US20120116382A1 - Catheter apparatuses having multi-electrode arrays for renal neuromodulation and associated systems and methods - Google Patents

Abstract

Catheter apparatuses, systems, and methods for achieving renal neuromodulation by intravascular access are disclosed herein. One aspect of the present technology, for example, is directed to a treatment device having a multi-electrode array configured to be delivered to a renal blood vessel. The array is selectively transformable between a delivery or low-profile state (e.g., a generally straight shape) and a deployed state (e.g., a radially expanded, generally helical shape). The multi-electrode array is sized and shaped so that the electrodes or energy delivery elements contact an interior wall of the renal blood vessel when the array is in the deployed (e.g., helical) state. The electrodes or energy delivery elements are configured for direct and/or indirect application of thermal and/or electrical energy to heat or otherwise electrically modulate neural fibers that contribute to renal function or of vascular structures that feed or perfuse the neural fibers.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)
• This application claims the benefit of the following pending applications:
• (a) U.S. Provisional Application No. 61/406,531, filed Oct. 25, 2010;
• (b) U.S. Provisional Application No. 61/406,960, filed Oct. 26, 2010;
• (c) U.S. Provisional Application No. 61/572,290, filed Jan. 28, 2011;
• (d) U.S. Provisional Application No. 61/528,001, filed Aug. 25, 2011;
• (e) U.S. Provisional Application No. 61/528,086, filed Aug. 26, 2011;
• (f) U.S. Provisional Application No. 61/528,091, filed Aug. 26, 2011;
• (g) U.S. Provisional Application No. 61/528,108, filed Aug. 26, 2011;
• (h) U.S. Provisional Application No. 61/528,684, filed Aug. 29, 2011; and
• (i) U.S. Provisional Application No. 61/546,512, filed Oct. 12, 2011.
• All of the foregoing applications are incorporated herein by reference in their entireties. Further, components and features of embodiments disclosed in the applications incorporated by reference may be combined with various components and features disclosed and claimed in the present application.
TECHNICAL FIELD
• The present technology relates generally to renal neuromodulation and associated systems and methods. In particular, several embodiments are directed to multi-electrode radio frequency (RF) ablation catheter apparatuses for intravascular renal neuromodulation and associated systems and methods.
BACKGROUND
• The sympathetic nervous system (SNS) is a primarily involuntary bodily control system typically associated with stress responses. Fibers of the SNS innervate tissue in almost every organ system of the human body and can affect characteristics such as pupil diameter, gut motility, and urinary output. Such regulation can have adaptive utility in maintaining homeostasis or in preparing the body for rapid response to environmental factors. Chronic activation of the SNS, however, is a common maladaptive response that can drive the progression of many disease states. Excessive activation of the renal SNS in particular has been identified experimentally and in humans as a likely contributor to the complex pathophysiology of hypertension, states of volume overload (such as heart failure), and progressive renal disease. For example, radiotracer dilution has demonstrated increased renal norepinephrine (NE) spillover rates in patients with essential hypertension.
• Cardio-renal sympathetic nerve hyperactivity can be particularly pronounced in patients with heart failure. For example, an exaggerated NE overflow from the heart and kidneys to plasma is often found in these patients. Heightened SNS activation commonly characterizes both chronic and end stage renal disease. In patients with end stage renal disease, NE plasma levels above the median have been demonstrated to be predictive for cardiovascular diseases and several causes of death. This is also true for patients suffering from diabetic or contrast nephropathy. Evidence suggests that sensory afferent signals originating from diseased kidneys are major contributors to initiating and sustaining elevated central sympathetic outflow.
• Sympathetic nerves innervating the kidneys terminate in the blood vessels, the juxtaglomerular apparatus, and the renal tubules. Stimulation of the renal sympathetic nerves can cause increased renin release, increased sodium (Na⁺) reabsorption, and a reduction of renal blood flow. These neural regulation components of renal function are considerably stimulated in disease states characterized by heightened sympathetic tone and likely contribute to increased blood pressure in hypertensive patients. The reduction of renal blood flow and glomerular filtration rate as a result of renal sympathetic efferent stimulation is likely a cornerstone of the loss of renal function in cardio-renal syndrome (i.e., renal dysfunction as a progressive complication of chronic heart failure). Pharmacologic strategies to thwart the consequences of renal efferent sympathetic stimulation include centrally acting sympatholytic drugs, beta blockers (intended to reduce renin release), angiotensin converting enzyme inhibitors and receptor blockers (intended to block the action of angiotensin II and aldosterone activation consequent to renin release), and diuretics (intended to counter the renal sympathetic mediated sodium and water retention). These pharmacologic strategies, however, have significant limitations including limited efficacy, compliance issues, side effects, and others. Accordingly, there is a strong public-health need for alternative treatment strategies.
BRIEF DESCRIPTION OF THE DRAWINGS
• Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on illustrating clearly the principles of the present disclosure.
• FIG. 1 illustrates an intravascular renal neuromodulation system configured in accordance with an embodiment of the present technology.
• FIG. 2 illustrates modulating renal nerves with a multi-electrode catheter apparatus in accordance with an embodiment of the present technology.
• FIG. 3A is a view of a distal portion of a catheter shaft and a multi-electrode array in a delivery state (e.g., low-profile or collapsed configuration) within a renal artery used in conjunction with a guide catheter in accordance with an embodiment of the present technology.
• FIG. 3B is a view of the distal portion of the catheter shaft and the multi-electrode array ofFIG. 3A in a deployed state (e.g., expanded configuration) within a renal artery in accordance with an embodiment of the technology.
• FIG. 3C is a partially cutaway, isometric view of a treatment device in a deployed state within a renal artery in accordance with an embodiment of the technology.
• FIG. 4A is a plan view of a treatment assembly for use in a treatment device in accordance with an embodiment of the technology.
• FIG. 4B is an isometric view of the treatment assembly ofFIG. 4A.
• FIG. 4C is an end view of the helical structure ofFIG. 4B showing the angular offset of energy delivery elements in a treatment assembly in accordance with an embodiment of the technology.
• FIG. 4D is a side view of a vessel with lesions prophetically formed by a treatment assembly that circumferentially and longitudinally overlap but do not overlap along a helical path.
• FIG. 5A-5D illustrate various embodiments of energy delivery elements or devices for use with the treatment assembly ofFIGS. 4A and 4B.
• FIG. 5E illustrates an embodiment of a treatment assembly in which the support structure is electrically conductive and serves as the energy delivery element.
• FIG. 6A illustrates an embodiment of a treatment device including an elongated shaft having different mechanical and functional regions configured in accordance with an embodiment of the technology.
• FIG. 6B is a plan view of a slot pattern for use in the treatment device ofFIG. 6A.
• FIG. 6C is a perspective view of a distal portion of the treatment device ofFIG. 6A in a delivery state (e.g., low-profile or collapsed configuration) outside a patient in accordance with an embodiment of the technology.
• FIG. 6D is a perspective view of the treatment device ofFIG. 6C in a deployed state (e.g., expanded configuration) outside a patient.
• FIG. 6E is a partially schematic plan view of a distal region of the support structure ofFIG. 6A in a generally helically-shaped deployed state.
• FIG. 6F is a partially schematic plan view of a distal portion of a treatment device of in a polygon-shaped deployed state in accordance with another embodiment of the technology.
• FIG. 6G is a plan view of a slot pattern for use in the treatment device ofFIG. 6A in accordance with another embodiment of the technology.
• FIG. 6H is a perspective view of a support structure for use in a treatment device configured in accordance with another embodiment of the technology.
• FIG. 6I is a plan view of an embodiment of a slot pattern for use in the support structure ofFIG. 6H.
• FIG. 6J is a plan view of a slot pattern for use with a treatment device configured in accordance with an embodiment of the technology.
• FIGS. 6K and 6L illustrate deformed slots of the support structure ofFIG. 6H in a deployed state in accordance with an embodiment of the technology.
• FIG. 6M is a plan view of a slot pattern for use with a treatment device configured in accordance with an embodiment of the technology.
• FIG. 6N is a plan view of a slot pattern for use with a treatment device configured in accordance with an embodiment of the technology.
• FIG. 6O is a schematic illustration of a portion of a treatment device having a support structure including the slot pattern ofFIG. 6N in a deployed state within a renal artery of a patient.
• FIG. 7A is a plan view of a hole pattern for use with a treatment device configured in accordance with an embodiment of the technology.
• FIG. 7B is a perspective view of a distal portion of a treatment device including a flexible region having the hole pattern ofFIG. 7A in a delivery state outside a patient.
• FIG. 8A is a broken perspective view in partial section of a treatment device including the slot pattern ofFIG. 6I configured in accordance with an embodiment of the technology.
• FIGS. 8B-8D illustrate various configurations of a distal end of a support structure configured in accordance with embodiments of the present technology.
• FIG. 9A illustrates a treatment device configured in accordance with an embodiment of the present technology in a deployed state (e.g., expanded configuration) outside a patient.
• FIG. 9B illustrates the treatment device ofFIG. 9A in a delivery state (e.g., low-profile or collapsed configuration).
• FIG. 9C illustrates another embodiment of a treatment device configured in accordance with an embodiment of the present technology in a deployed state.
• FIG. 9D illustrates yet another embodiment of a treatment device in a delivery state.
• FIG. 9E illustrates the device ofFIG. 9D in a deployed state.
• FIG. 10A is broken plan view of another treatment device in a delivery state outside a patient in accordance with an embodiment of the technology.
• FIG. 10B is a detailed view of a distal portion of the device ofFIG. 10A in a deployed state.
• FIG. 11A is a broken side view in part section of a treatment device in a delivery state in accordance with another embodiment of the technology.
• FIG. 11B is a broken side view in part section of the treatment device ofFIG. 11A in a deployed state.
• FIG. 11C is a longitudinal cross-sectional view of a handle assembly for use in the device ofFIG. 11A in accordance with an embodiment of the present technology.
• FIG. 11D is a longitudinal cross-sectional view of another handle assembly for use in the device ofFIG. 11A in accordance with an embodiment of the present technology.
• FIG. 12A is a side view of a distal portion of a treatment device in a delivery state (e.g., low-profile or collapsed configuration) outside a patient in accordance with an embodiment of the present technology.
• FIG. 12B is a side view of the distal portion of the treatment device ofFIG. 12B in a deployed state (e.g., expanded configuration) outside the patient.
• FIG. 13A is a broken side view in part section of a treatment device in a delivery state in accordance an embodiment of the present technology.
• FIG. 13B is a broken side view in part section of the embodiment ofFIG. 13A in a deployed state within a renal artery.
• FIG. 14A is a broken longitudinal cross-sectional view of another embodiment of a treatment device in a delivery state in accordance an embodiment of the present technology.
• FIG. 14B is a broken side view in part section of the embodiment ofFIG. 14A in a deployed state within a renal artery.
• FIG. 14C is a longitudinal cross-sectional view of a distal portion of another embodiment of a treatment device in a delivery state in accordance an embodiment of the present technology.
• FIG. 14D is a broken longitudinal cross-sectional view of the embodiment ofFIG. 14C in a deployed state within a renal artery.
• FIG. 15A is a longitudinal cross-sectional view of a distal portion of another embodiment of a treatment device in a delivery state in accordance an embodiment of the present technology.
• FIG. 15B is a broken side view in part section of the embodiment ofFIG. 15A in a deployed state within a renal artery.
• FIG. 16A is a cross-sectional view of one embodiment a treatment device in a delivery state within a patient's renal artery in accordance an embodiment of the present technology.
• FIG. 16B is a cross-sectional view of one embodiment a treatment device in a deployed state within a patient's renal artery in accordance an embodiment of the present technology.
• FIG. 17A is a broken side view in part section of a distal portion a rapid-exchange type of a treatment device configured in accordance an embodiment of the present technology.
• FIG. 17B is a broken side view in part section of a distal portion of a rapid-exchange type of a treatment device in a delivery state in accordance an embodiment of the present technology.
• FIG. 17C is a broken side view of a distal portion of the treatment device ofFIG. 17B in a deployed state.
• FIG. 17C is a broken side view in part section of a distal portion of another embodiment of a rapid-exchange type of a treatment device in accordance an embodiment of the present technology.
• FIG. 17D is a broken side view in part section of a distal portion of another rapid-exchange type of a treatment device in accordance an embodiment of the present technology.
• FIG. 17E is a broken side view in part section of a distal portion of yet another embodiment of a rapid-exchange type of a treatment device in accordance an embodiment of the present technology.
• FIG. 18 is an illustration of theoretical blood flow in a renal artery in accordance with an embodiment of the technology.
• FIG. 19A is a cross-sectional view of a treatment assembly including a fluid redirecting element within a renal artery in accordance with an embodiment of the present technology.
• FIG. 19B is a side view of a support structure with a schematic illustration of a fluid redirecting element in a delivery state (e.g., low-profile or collapsed configuration) outside a patient in accordance with an embodiment of the present technology.
• FIG. 20 is a graph depicting an energy delivery algorithm that may be used in conjunction with the system ofFIG. 1 in accordance with an embodiment of the technology.
• FIGS. 21 and 22 are block diagrams illustrating algorithms for evaluating a treatment in accordance with embodiments of the present technology.
• FIG. 23 is a block diagram illustrating an algorithm for providing operator feedback upon occurrence of a high temperature condition in accordance with an embodiment of the present technology.
• FIG. 24 is a block diagram illustrating an algorithm for providing operator feedback upon occurrence of a high impedance condition in accordance with an embodiment of the present technology.
• FIG. 25 is a block diagram illustrating an algorithm for providing operator feedback upon occurrence of a high degree of vessel constriction in accordance with an embodiment of the present technology.
• FIG. 26A is a block diagram illustrating an algorithm for providing operator feedback upon occurrence of an abnormal heart rate condition in accordance with an embodiment of the present technology.
• FIG. 26B is a block diagram illustrating an algorithm for providing operator feedback upon occurrence of a low blood flow condition in accordance with an embodiment of the present technology.
• FIGS. 27A and 27B are screen shots illustrating representative generator display screens configured in accordance with aspects of the present technology.
• FIG. 28 is an illustration of a kit containing packaged components of the system ofFIG. 1 in accordance with an embodiment of the technology.
• FIG. 29 is a conceptual illustration of the sympathetic nervous system (SNS) and how the brain communicates with the body via the SNS.
• FIG. 30 is an enlarged anatomic view of nerves innervating a left kidney to form the renal plexus surrounding the left renal artery.
• FIGS. 31A and 31B provide anatomic and conceptual views of a human body, respectively, depicting neural efferent and afferent communication between the brain and kidneys.
• FIGS. 32A and 32B are, respectively, anatomic views of the arterial and venous vasculatures of a human.
DETAILED DESCRIPTION
• The present technology is directed to apparatuses, systems, and methods for achieving electrically- and/or thermally-induced renal neuromodulation (i.e., rendering neural fibers that innervate the kidney inert or inactive or otherwise completely or partially reduced in function) by percutaneous transluminal intravascular access. In particular, embodiments of the present technology relate to apparatuses, systems, and methods that incorporate a catheter treatment device having a multi-electrode array movable between a delivery or low-profile state (e.g., a generally straight shape) and a deployed state (e.g., a radially expanded, generally helical shape). The electrodes or energy delivery elements carried by the array are configured to deliver energy (e.g., electrical energy, radio frequency (RF) electrical energy, pulsed electrical energy, thermal energy) to a renal artery after being advanced via catheter along a percutaneous transluminal path (e.g., a femoral artery puncture, an iliac artery and the aorta, a radial artery, or another suitable intravascular path). The multi-electrode array is sized and shaped so that the electrodes or energy delivery elements contact an interior wall of the renal artery when the array is in the deployed (e.g., helical) state within the renal artery. In addition, the helical shape of the deployed array allows blood to flow through the helix, which is expected to help prevent occlusion of the renal artery during activation of the energy delivery element. Further, blood flow in and around the array may cool the associated electrodes and/or the surrounding tissue. In some embodiments, cooling the energy delivery elements allows for the delivery of higher power levels at lower temperatures than may be reached without cooling. This feature is expected to help create deeper and/or larger lesions during therapy, reduce intimal surface temperature, and/or allow longer activation times with reduced risk of overheating during treatment.
• Specific details of several embodiments of the technology are described below with reference toFIGS. 1-32B. Although many of the embodiments are described below with respect to devices, systems, and methods for intravascular modulation of renal nerves using multi-electrode arrays, other applications and other embodiments in addition to those described herein are within the scope of the technology. Additionally, several other embodiments of the technology can have different configurations, components, or procedures than those described herein. A person of ordinary skill in the art, therefore, will accordingly understand that the technology can have other embodiments with additional elements, or the technology can have other embodiments without several of the features shown and described below with reference toFIGS. 1-32B.
• As used herein, the terms “distal” and “proximal” define a position or direction with respect to the treating clinician or clinician's control device (e.g., a handle assembly). “Distal” or “distally” are a position distant from or in a direction away from the clinician or clinician's control device. “Proximal” and “proximally” are a position near or in a direction toward the clinician or clinician's control device.
I. RENAL NEUROMODULATION
• Renal neuromodulation is the partial or complete incapacitation or other effective disruption of nerves innervating the kidneys. In particular, renal neuromodulation comprises inhibiting, reducing, and/or blocking neural communication along neural fibers (i.e., efferent and/or afferent nerve fibers) innervating the kidneys. Such incapacitation can be long-term (e.g., permanent or for periods of months, years, or decades) or short-term (e.g., for periods of minutes, hours, days, or weeks). Renal neuromodulation is expected to efficaciously treat several clinical conditions characterized by increased overall sympathetic activity, and in particular conditions associated with central sympathetic over stimulation such as hypertension, heart failure, acute myocardial infarction, metabolic syndrome, insulin resistance, diabetes, left ventricular hypertrophy, chronic and end stage renal disease, inappropriate fluid retention in heart failure, cardio-renal syndrome, and sudden death. The reduction of afferent neural signals contributes to the systemic reduction of sympathetic tone/drive, and renal neuromodulation is expected to be useful in treating several conditions associated with systemic sympathetic over activity or hyperactivity. Renal neuromodulation can potentially benefit a variety of organs and bodily structures innervated by sympathetic nerves. For example, a reduction in central sympathetic drive may reduce insulin resistance that afflicts patients with metabolic syndrome and Type II diabetics. Additionally, osteoporosis can be sympathetically activated and might benefit from the downregulation of sympathetic drive that accompanies renal neuromodulation. A more detailed description of pertinent patient anatomy and physiology is provided in Section IX below.
• Various techniques can be used to partially or completely incapacitate neural pathways, such as those innervating the kidney. The purposeful application of energy (e.g., electrical energy, thermal energy) to tissue by energy delivery element(s) can induce one or more desired thermal heating effects on localized regions of the renal artery and adjacent regions of the renal plexus RP, which lay intimately within or adjacent to the adventitia of the renal artery. The purposeful application of the thermal heating effects can achieve neuromodulation along all or a portion of the renal plexus RP.
• The thermal heating effects can include both thermal ablation and non-ablative thermal alteration or damage (e.g., via sustained heating and/or resistive heating). Desired thermal heating effects may include raising the temperature of target neural fibers above a desired threshold to achieve non-ablative thermal alteration, or above a higher temperature to achieve ablative thermal alteration. For example, the target temperature can be above body temperature (e.g., approximately 37° C.) but less than about 45° C. for non-ablative thermal alteration, or the target temperature can be about 45° C. or higher for the ablative thermal alteration.
• More specifically, exposure to thermal energy (heat) in excess of a body temperature of about 37° C., but below a temperature of about 45° C., may induce thermal alteration via moderate heating of the target neural fibers or of vascular structures that perfuse the target fibers. In cases where vascular structures are affected, the target neural fibers are denied perfusion resulting in necrosis of the neural tissue. For example, this may induce non-ablative thermal alteration in the fibers or structures. Exposure to heat above a temperature of about 45° C., or above about 60° C., may induce thermal alteration via substantial heating of the fibers or structures. For example, such higher temperatures may thermally ablate the target neural fibers or the vascular structures. In some patients, it may be desirable to achieve temperatures that thermally ablate the target neural fibers or the vascular structures, but that are less than about 90° C., or less than about 85° C., or less than about 80° C., and/or less than about 75° C. Regardless of the type of heat exposure utilized to induce the thermal neuromodulation, a reduction in renal sympathetic nerve activity (“RSNA”) is expected.
II. SELECTED EMBODIMENTS OF CATHETER APPARATUSES HAVING MULTI-ELECTRODE ARRAYS
• FIG. 1 illustrates a renal neuromodulation system10 (“system10”) configured in accordance with an embodiment of the present technology. Thesystem10 includes anintravascular treatment device12 operably coupled to an energy source orenergy generator26. In the embodiment shown inFIG. 1, the treatment device12 (e.g., a catheter) includes anelongated shaft16 having aproximal portion18, ahandle34 at a proximal region of theproximal portion18, and adistal portion20 extending distally relative to theproximal portion18. Thetreatment device12 further includes a therapeutic assembly ortreatment section21 at thedistal portion20 of theshaft16. As explained in further detail below, thetherapeutic assembly21 can include an array of two or more electrodes orenergy delivery elements24 configured to be delivered to a renal blood vessel (e.g., a renal artery) in a low-profile configuration. Upon delivery to the target treatment site within the renal blood vessel, thetherapeutic assembly21 is further configured to be deployed into an expanded state (e.g., a generally helical or spiral configuration) for delivering energy at the treatment site and providing therapeutically-effective electrically- and/or thermally-induced renal neuromodulation. Alternatively, the deployed state may be non-helical provided that the deployed state delivers the energy to the treatment site. In some embodiments, thetherapeutic assembly21 may be placed or transformed into the deployed state or arrangement via remote actuation, e.g., via anactuator36, such as a knob, pin, or lever carried by thehandle34. In other embodiments, however, thetherapeutic assembly21 may be transformed between the delivery and deployed states using other suitable mechanisms or techniques.
• The proximal end of thetherapeutic assembly21 is carried by or affixed to thedistal portion20 of theelongated shaft16. A distal end of thetherapeutic assembly21 may terminate thetreatment device12 with, for example, an atraumatic rounded tip or cap. Alternatively, the distal end of thetherapeutic assembly21 may be configured to engage another element of thesystem10 ortreatment device12. For example, the distal end of thetherapeutic assembly21 may define a passageway for engaging a guide wire (not shown) for delivery of the treatment device using over-the-wire (“OTW”) or rapid exchange (“RX”) techniques. Further details regarding such arrangements are described below with reference toFIGS. 9A-17E.
• The energy source or energy generator26 (e.g., a RF energy generator) is configured to generate a selected form and magnitude of energy for delivery to the target treatment site via theenergy delivery elements24. Theenergy generator26 can be electrically coupled to thetreatment device12 via acable28. At least one supply wire (not shown) passes along theelongated shaft16 or through a lumen in theelongated shaft16 to theenergy delivery elements24 and transmits the treatment energy to theenergy delivery elements24. In some embodiments, eachenergy delivery element24 includes its own supply wire. In other embodiments, however, two or moreenergy delivery elements24 may be electrically coupled to the same supply wire. A control mechanism, such asfoot pedal32, may be connected (e.g., pneumatically connected or electrically connected) to theenergy generator26 to allow the operator to initiate, terminate and, optionally, adjust various operational characteristics of the generator, including, but not limited to, power delivery. Thesystem10 may also include a remote control device (not shown) that can be positioned in a sterile field and operably coupled to theenergy delivery elements24. The remote control device is configured to allow for selectively turning on/off the electrodes. In other embodiments, the remote control device may be built into thehandle assembly34. Theenergy generator26 can be configured to deliver the treatment energy via anautomated control algorithm30 and/or under the control of the clinician. In addition, theenergy generator26 may include one or more evaluation orfeedback algorithms31 to provide feedback to the clinician before, during, and/or after therapy. Further details regarding suitable control algorithms and evaluation/feedback algorithms are described below with reference toFIGS. 20-27.
• In some embodiments, thesystem10 may be configured to provide delivery of a monopolar electric field via theenergy delivery elements24. In such embodiments, a neutral ordispersive electrode38 may be electrically connected to theenergy generator26 and attached to the exterior of the patient (as shown inFIG. 2). Additionally, one or more sensors (not shown), such as one or more temperature (e.g., thermocouple, thermistor, etc.), impedance, pressure, optical, flow, chemical or other sensors, may be located proximate to or within theenergy delivery elements24 and connected to one or more supply wires (not shown). For example, a total of two supply wires may be included, in which both wires could transmit the signal from the sensor and one wire could serve dual purpose and also convey the energy to theenergy delivery elements24. Alternatively, a different number of supply wires may be used to transmit energy to theenergy delivery elements24.
• Theenergy generator26 may be part of a device or monitor that may include processing circuitry, such as a microprocessor, and a display. The processing circuitry may be configured to execute stored instructions relating to thecontrol algorithm30. The monitor may be configured to communicate with the treatment device12 (e.g., via cable28) to control power to theenergy delivery elements24 and/or to obtain signals from theenergy delivery elements24 or any associated sensors. The monitor may be configured to provide indications of power levels or sensor data, such as audio, visual or other indications, or may be configured to communicate the information to another device. For example, theenergy generator26 may also be configured to be operably coupled to a catheter lab screen or system for displaying treatment information.
• FIG. 2 (with additional reference toFIG. 30) illustrates modulating renal nerves with an embodiment of thesystem10. Thetreatment device12 provides access to the renal plexus RP through an intravascular path P, such as a percutaneous access site in the femoral (illustrated), brachial, radial, or axillary artery to a targeted treatment site within a respective renal artery RA. As illustrated, a section of theproximal portion18 of theshaft16 is exposed externally of the patient. By manipulating theproximal portion18 of theshaft16 from outside the intravascular path P, the clinician may advance theshaft16 through the sometimes tortuous intravascular path P and remotely manipulate thedistal portion20 of theshaft16. Image guidance, e.g., computed tomography (CT), fluoroscopy, intravascular ultrasound (IVUS), optical coherence tomography (OCT), or another suitable guidance modality, or combinations thereof, may be used to aid the clinician's manipulation. Further, in some embodiments, image guidance components (e.g., IVUS, OCT) may be incorporated into thetreatment device12 itself. After thetherapeutic assembly21 is adequately positioned in the renal artery RA, it can be radially expanded or otherwise deployed using thehandle34 or other suitable means until theenergy delivery elements24 are in stable contact with the inner wall of the renal artery RA. The purposeful application of energy from theenergy delivery elements24 is then applied to tissue to induce one or more desired neuromodulating effects on localized regions of the renal artery and adjacent regions of the renal plexus RP, which lay intimately within, adjacent to, or in close proximity to the adventitia of the renal artery RA. The purposeful application of the energy may achieve neuromodulation along all or at least a portion of the renal plexus RP.
• The neuromodulating effects are generally a function of, at least in part, power, time, contact between theenergy delivery elements24 and the vessel wall, and blood flow through the vessel. The neuromodulating effects may include denervation, thermal ablation, and non-ablative thermal alteration or damage (e.g., via sustained heating and/or resistive heating). Desired thermal heating effects may include raising the temperature of target neural fibers above a desired threshold to achieve non-ablative thermal alteration, or above a higher temperature to achieve ablative thermal alteration. For example, the target temperature may be above body temperature (e.g., approximately 37° C.) but less than about 45° C. for non-ablative thermal alteration, or the target temperature may be about 45° C. or higher for the ablative thermal alteration. Desired non-thermal neuromodulation effects may include altering the electrical signals transmitted in a nerve.
• In some embodiments, theenergy delivery elements24 of thetherapeutic assembly21 may be proximate to, adjacent to, or carried by (e.g., adhered to, threaded over, wound over, and/or crimped to) asupport structure22. The proximal end of thesupport structure22 is preferably coupled to thedistal portion20 of theelongated shaft16 via a coupling (not shown). The coupling may be an integral component of the elongated shaft16 (i.e., may not be a separate piece) or the coupling may be a separate piece such as a collar (e.g., a radiopaque band) wrapped around an exterior surface of theelongated shaft16 to secure thesupport structure22 to theelongated shaft16. In other embodiments, however, thesupport structure22 may be associated with theelongated shaft16 using another arrangement and/or different features.
• In still another embodiment, theenergy delivery elements24 may form or define selected portions of, or the entirety of, thesupport structure22 itself. That is, as is described in further detail below, thesupport structure22 may be capable of delivering energy. Moreover, although in some embodiments thetherapeutic assembly21 may function with a single energy delivery element, it will be appreciated that thetherapeutic assembly21 preferably includes a plurality ofenergy delivery elements24 associated with or defining thesupport structure22. When multipleenergy delivery elements24 are provided, theenergy delivery elements24 may deliver power independently (i.e., may be used in a monopolar fashion), either simultaneously, selectively, or sequentially, and/or may deliver power between any desired combination of the elements (i.e., may be used in a bipolar fashion). Furthermore, the clinician optionally may choose which energy delivery element(s)24 are used for power delivery in order to form highly customized lesion(s) within the renal artery having a variety of shapes or patterns.
• FIG. 3A is a cross-sectional view illustrating one embodiment of thedistal portion20 of theshaft16 and thetherapeutic assembly21 in a delivery state (e.g., low-profile or collapsed configuration) within a renal artery RA, andFIGS. 3B and 3C illustrate thetherapeutic assembly21 in a deployed state (e.g., expanded or helical configuration) within the renal artery. Referring first toFIG. 3A, the collapsed or delivery arrangement of thetherapeutic assembly21 defines a low profile about the longitudinal axis A-A of the assembly such that a transverse dimension of thetherapeutic assembly21 is sufficiently small to define a clearance distance between anarterial wall55 and thetreatment device12. The delivery state facilitates insertion and/or removal of thetreatment device12 and, if desired, repositioning of thetherapeutic assembly21 within the renal artery RA.
• In the collapsed configuration, for example, the geometry of thesupport structure22 facilitates movement of thetherapeutic assembly21 through aguide catheter90 to the treatment site in the renal artery RA. Moreover, in the collapsed configuration, thetherapeutic assembly21 is sized and shaped to fit within the renal artery RA and has a diameter that is less than a renal artery inner diameter52 and a length (from a proximal end of thetherapeutic assembly21 to a distal end of the therapeutic assembly21) that is less than arenal artery length54. Further, as described in greater detail below, the geometry of thesupport structure22 is also arranged to define (in the delivery state) a minimum transverse dimension about its central axis that is less than the renal artery inner diameter52 and a maximum length in the direction of the central axis that is preferably less than therenal artery length54. In one embodiment, for example, the minimum diameter of thetherapeutic assembly21 is approximately equal to the interior diameter of theelongated shaft16.
• Thedistal portion20 of theshaft16 may flex in a substantial fashion to gain entrance into a respective left/right renal artery by following a path defined by a guide catheter, a guide wire, or a sheath. For example, the flexing ofdistal portion20 may be imparted by theguide catheter90, such as a renal guide catheter with a preformed bend near the distal end that directs theshaft16 along a desired path, from the percutaneous insertion site to the renal artery RA. In another embodiment, thetreatment device12 may be directed to the treatment site within the renal artery RA by engaging and tracking a guide wire (e.g.,guide wire66 ofFIG. 2) that is inserted into the renal artery RA and extends to the percutaneous access site. In operation, the guide wire is preferably first delivered into the renal artery RA and theelongated shaft16 comprising a guide wire lumen is then passed over the guide wire into the renal artery RA. In some guide wire procedures, a tubular delivery sheath1291 (described in greater detail below with reference toFIGS. 16A and 16B) is passed over the guide wire (i.e., the lumen defined by the delivery sheath slides over the guide wire) into the renal artery RA. Once the delivery sheath1291 (FIG. 16A) is placed in the renal artery RA, the guide wire may be removed and exchanged for a treatment catheter (e.g., treatment device12) that may be delivered through thedelivery sheath1291 into the renal artery RA. Furthermore, in some embodiments, thedistal portion20 can be directed or “steered” into the renal artery RA via the handle assembly34 (FIGS. 1 and 2), for example, by anactuatable element36 or by another control element. In particular, the flexing of theelongated shaft16 may be accomplished as provided in U.S. patent application Ser. No. 12/545,648, “Apparatus, Systems, and Methods for achieving Intravascular, Thermally-Induced Renal Neuromodulation” to Wu et al., which is incorporated herein by reference in its entirety. Alternatively, or in addition, thetreatment device12 and itsdistal portion20 may be flexed by being inserted through a steerable guide catheter (not shown) that includes a preformed or steerable bend near its distal end that can be adjusted or re-shaped by manipulation from the proximal end of the guide catheter.
• The maximum outer dimension (e.g., diameter) of any section of thetreatment device12, includingelongated shaft16 and theenergy delivery elements24 of thetherapeutic assembly21 can be defined by an inner diameter of theguide catheter90 through which thedevice12 is passed. In one particular embodiment, for example, an 8 French guide catheter having, for example, an inner diameter of approximately 0.091 inch (2.31 mm) may be used as a guide catheter to access the renal artery. Allowing for a reasonable clearance tolerance between theenergy delivery elements24 and the guide catheter, the maximum outer dimension of thetherapeutic assembly21 is generally less than or equal to approximately 0.085 inch (2.16 mm). For a therapeutic assembly having a substantially helical support structure for carrying theenergy delivery elements24, the expanded or helical configuration preferably defines a maximum width of less than or equal to approximately 0.085 inch (2.16 mm). However, use of a smaller 5 French guide catheter may require the use of smaller outer diameters along thetreatment device12. For example, atherapeutic assembly21 having ahelical support structure22 that is to be routed within a 5 French guide catheter preferably has an outer dimension or maximum width of no greater than about 0.053 inch (1.35 mm). In still other embodiments, it may be desirable to have atherapeutic assembly21 with a maximum width substantially under 0.053 inch (1.35 mm) provided there is sufficient clearance between the energy delivery elements and the guide catheter. Moreover, in some embodiments it may be desirable to have an arrangement in which the guide catheter and thetherapeutic assembly21 define a ratio of diameters of about 1.5:1. In another example, the helical structure andenergy delivery element24 that are to be delivered within a 6 French guide catheter would have an outer dimension of no great than 0.070 inch (1.78 mm). In still further examples, other suitable guide catheters may be used, and outer dimensions and/or arrangements of thetreatment device12 can vary accordingly.
• After locating thetherapeutic assembly21 at thedistal portion20 of theshaft16 in the renal artery RA, thetherapeutic assembly21 is transformed from its delivery state to its deployed state or deployed arrangement. The transformation may be initiated using an arrangement of device components as described herein with respect to the particular embodiments and their various modes of deployment. As described in greater detail below and in accordance with one or more embodiments of the present technology, the therapeutic assembly may be deployed by a control member, such as for example a pull- or tension-wire, guide wire, shaft or stylet engaged internally or externally with the support structure of the therapeutic assembly to apply a deforming or shaping force to the assembly to transform it into its deployed state. Alternatively, thetherapeutic assembly21 may be self expanding or deploying such that removal of a radial restraint results in deployment of the assembly. Further, the modality used to transform thetherapeutic assembly21 from the delivery state into the deployed state may, in most embodiments, be reversed to transform thetherapeutic assembly21 back to the delivery state from the deployed state.
• Further manipulation of thesupport structure22 and theenergy delivery elements24 within the respective renal artery RA establishes apposition of theenergy delivery elements24 against the tissue along an interior wall of the respective renal artery RA. For example, as shown inFIGS. 3B and 3C, thetherapeutic assembly21 is expanded within the renal artery RA such that theenergy delivery elements24 are in contact with therenal artery wall55. In some embodiments, manipulation of thedistal portion20 will also facilitate contact between theenergy delivery elements24 and the wall of the renal artery. Embodiments of the support structures described herein (e.g., the support structure22) are expected to ensure that the contact force between the renal arteryinner wall55 and theenergy delivery elements24 does not exceed a maximum value. In addition, thesupport structure22 or other suitable support structures described herein preferably provide for a consistent contact force against thearterial wall55 that may allow for consistent lesion formation.
• The alignment may also include alignment of geometrical aspects of theenergy delivery elements24 with therenal artery wall55. For example, in embodiments in which theenergy delivery elements24 have a cylindrical shape with rounded ends, alignment may include alignment of the longitudinal surface of the individualenergy delivery elements24 with theartery wall55. In another example, an embodiment may compriseenergy delivery elements24 having a structured shape or inactive surface, and alignment may include aligning theenergy delivery elements24 such that the structured shape or inactive surface is not in contact with theartery wall55.
• As best seen inFIGS. 3B and 3C, in the deployed state, thetherapeutic assembly21 defines a substantiallyhelical support structure22 in contact with therenal artery wall55 along a helical path. One advantage of this arrangement is that pressure from the helical structure can be applied to a large range of radial directions without applying pressure to a circumference of the vessel. Thus, the helically-shapedtherapeutic assembly21 is expected to provide stable contact between theenergy delivery elements24 and theartery wall55 when the wall moves in any direction. Furthermore, pressure applied to thevessel wall55 along a helical path is less likely to stretch or distend a circumference of a vessel that could thereby cause injury to the vessel tissue. Still another feature of the expanded helical structure is that it may contact the vessel wall in a large range of radial directions and maintain a sufficiently open lumen in the vessel allowing blood to flow through the helix during therapy.
• As best seen inFIG. 3B, in the deployed state, thesupport structure22 defines a maximum axial length of thetherapeutic assembly21 that is approximately equal to or less than arenal artery length54 of a main renal artery (i.e., a section of a renal artery proximal to a bifurcation). Because this length can vary from patient to patient, it is envisioned that the deployed helical-shapedsupport structure22 may be fabricated in different sizes (e.g., with varying lengths L and/or diameters D as shown inFIG. 4A) that may be appropriate for different patients. Referring toFIGS. 3B and 3C, in the deployed state, the helical-shapedtherapeutic assembly21 provides for circumferentially discontinuous contact between theenergy delivery elements24 and theinner wall55 of the renal artery RA. That is, the helical path may comprise a partial arc (i.e., <360°), a complete arc (i.e., 360°) or a more than complete arc (i.e., >360°) along the inner wall of a vessel about the longitudinal axis of the vessel. In some embodiments, however, the arc is not substantially in one plane normal to the central axis of the artery, but instead preferably defines an obtuse angle with the central axis of the artery.
• A. The Helical Structure
• FIG. 4A is a plan view of an embodiment of a therapeutic ortreatment assembly21 for use with a treatment device (e.g., treatment device12) in accordance with an embodiment of the technology, andFIG. 4B is an isometric view of thetherapeutic assembly21 ofFIG. 4A. Theenergy delivery elements24 depicted inFIGS. 4A and 4B are merely for illustrative purposes, and it will be appreciated that thetreatment assembly21 can include a different number and/or arrangement ofenergy delivery elements24.
• As shown inFIGS. 4A and 4B, a helix may be characterized, at least in part, by its overall diameter D, length L, helix angle α (an angle between a tangent line to the helix and its axis), pitch HP (longitudinal distance of one complete helix turn measured parallel to its axis), and number of revolutions (number of times the helix completes a 360° revolution about its axis).
• In particular, the deployed or expanded configuration of the helix may be characterized by its axial length L along the axis of elongation in free space, e.g., not restricted by a vessel wall or other structure. As thehelical support structure22 radially expands from its delivery state, its diameter D increases and its length L decreases. That is, when the helical structure deploys, adistal end22amoves axially towards theproximal end22b(or vice versa). Accordingly, the deployed length L is less than the unexpanded or delivery length. In certain embodiments, only one of thedistal end portion22aor theproximal end portion22bof thesupport structure22 is fixedly coupled to theelongated shaft16 or an extension thereof. In other embodiments, thesupport structure22 may be transformed to its deployed or expanded configuration by twisting the distal andproximal end portions22aand22brelative to one another.
• Referring toFIG. 4B, the deployed helically-shapedsupport structure22 optionally comprises adistal extension26adistal to the helical portion that is relatively straight and may terminate with an atraumatic (e.g., rounded)tip50. Thedistal extension26aincluding thetip50 may reduce the risk of injuring the blood vessel as the helical structure is expanding and/or as a delivery sheath is retracted, and may facilitate alignment of the helical structure in a vessel as it expands. In some embodiments, thedistal extension26ais generally straight (but flexible) and has a length of less than about 40 mm (e.g., between 2 mm and 10 mm). Thetip50 can be made from a polymer or metal that is fixed to the end of the structural element by adhesive, welding, crimping, over-molding, and/or solder. In other embodiments, thetip50 may be made from the same material as the structural element and fabricated into thetip50 by machining or melting. In other embodiments, thedistal extension26amay have a different configuration and/or features. For example, in some embodiments thetip50 may comprise an energy delivery element or a radiopaque marker. Further, thedistal extension26ais an optional feature that may not be included in all embodiments.
• The helical structure may also optionally have aproximal extension26bthat is relatively straight compared to the helically shaped region of thesupport structure22. Theproximal extension26b, for example, may be an extension of thesupport structure22 and may have a length between 0 mm and 40 mm (e.g., between about 2 and 10 mm). Alternatively, theproximal extension26bmay be comprised of a separate material (e.g., a polymer fiber) with more flexibility than the rest of thesupport structure22. Theproximal extension26bis configured to provide a flexible connection between the helical region of thesupport structure22 and the distal end of the elongated shaft16 (FIG. 1). This feature is expected to facilitate alignment of the deployedhelical support structure22 with the vessel wall by reducing the force transferred from theelongated shaft16 to the helical region of thehelical structure22. This may be useful, for example, when the elongated shaft is biased toward a side of the vessel wall or if the elongated shaft moves relative to the vessel wall allowing the helical structure to remain positioned.
• Referring back toFIGS. 4A and 4B together (and with reference toFIGS. 3A and 3B), the dimensions of the deployed helically-shapedstructure22 are influenced by its physical characteristics and its configuration (e.g., expanded vs. unexpanded), which in turn may be selected with renal artery geometry in mind. For example, the axial length L of the deployed helical structure may be selected to be no longer than a patient's renal artery (e.g., thelength54 of renal artery RA ofFIGS. 3A and 3B). For example, the distance between the access site and the ostium of the renal artery (e.g., the distance from a femoral access site to the renal artery is typically about 40 cm to about 55 cm) is generally greater than the length of a renal artery from the aorta and the most distal treatment site along the length of the renal artery, which is typically less than about 7 cm. Accordingly, it is envisioned that the elongated shaft16 (FIG. 1) is at least 40 cm and the helical structure is less than about 7 cm in its unexpanded length L. A length in an unexpanded configuration of no more than about 4 cm may be suitable for use in a large population of patients and provide a long contact area when in an expanded configuration and, in some embodiments, provide a long region for placement of multiple energy delivery elements; however, a shorter length (e.g., less than about 2 cm) in an unexpanded configuration may be used in patients with shorter renal arteries. Thehelical structure22 may also be designed to work with typical renal artery diameters. For example, the diameter52 (FIG. 3A) of the renal artery RA may vary between about 2 mm and about 10 mm. In a particular embodiment, the placement of theenergy delivery elements24 on thehelical structure22 may be selected with regard to an estimated location of the renal plexus RP relative to the renal artery RA.
• In another specific embodiment, a section or support structure of thetherapeutic assembly21, when allowed to fully deploy to an unconstrained configuration (i.e., outside of the body as shown inFIGS. 4A and 4B), comprises a helical shape having a diameter D less than about 15 mm (e.g., about 12 mm, 10 mm, 8 mm, or 6 mm); a length L less than or equal to about 40 mm (e.g., less than about 25 mm, less than about 20 mm, less than about 15 mm); a helix angle α of between about 20° and 75° (e.g., between about 35° and 55°); a range of revolutions between 0.25 and 6 (e.g., between 0.75 and 2, between 0.75 and 1.25); and a pitch HP between about 5 mm and 20 mm (e.g., between about 7 mm and 13 mm). In another example, thetherapeutic assembly21 may be configured to expand radially from its delivery state with a diameter about its central axis being approximately 10 mm to a delivery state in which theenergy delivery elements24 are in contact with the artery wall. The foregoing dimensions/angles are associated with specific embodiments of the technology, and it will be appreciated that therapeutic assemblies configured in accordance with other embodiments of the technology may have different arrangements and/or configurations.
• In some embodiments, the deployed helically-shapedsupport structure22 may be generally cylindrical (i.e., a helical diameter can be generally consistent along a majority of its length). It is also contemplated, however, that thestructure22 may have variations such as a conical helical shape, a tapered structural element, clockwise or counterclockwise pathway, consistent or varied pitch.
• In one embodiment, thesupport structure22 can include a solid structural element, e.g., a wire, tube, coiled or braided cable. Thesupport structure22 may be formed from biocompatible metals and/or polymers, including polyethylene terephthalate (PET), polyamide, polyimide, polyethylene block amide copolymer, polypropylene, or polyether ether ketone (PEEK) polymers. In some embodiments, thesupport structure22 may be electrically nonconductive, electrically conductive (e.g., stainless steel, nitinol, silver, platinum, nickel-cobalt-chromium-molybdenum alloy), or a combination of electrically conductive and nonconductive materials. In one particular embodiment, for example, thesupport structure22 may be formed of a pre-shaped material, such as spring temper stainless steel or nitinol. Furthermore, in particular embodiments, thestructure22 may be formed, at least in part, from radiopaque materials that are capable of being fluoroscopically imaged to allow a clinician to determine if thetreatment assembly21 is appropriately placed and/or deployed in the renal artery. Radiopaque materials may include, for example, barium sulfate, bismuth trioxide, bismuth subcarbonate, powdered tungsten, powdered tantalum, or various formulations of certain metals, including gold and platinum, and these materials may be directly incorporated intostructural elements22 or may form a partial or complete coating on thehelical structure22.
• Generally, thehelical structure22 may be designed to apply a desired outward radial force to the renal artery wall55 (FIGS. 3A and 3B) when inserted and expanded to contact the inner surface of the renal artery wall55 (FIGS. 3A and 3B). The radial force may be selected to avoid injury from stretching or distending the renal artery RA when thehelical structure22 is expanded against theartery wall55 within the patient. Radial forces that may avoid injuring the renal artery RA yet provide adequate stabilization force may be determined by calculating the radial force exerted on an artery wall by typical blood pressure. For example, a suitable radial force may be less than or equal to about 300 mN/mm (e.g., less than 200 mN/mm). Factors that may influence the applied radial force include the geometry and the stiffness of thesupport structure22. In one particular embodiment, thesupport structure22 is about 0.003-0.009 inch (0.08-0.23 mm) in diameter. Depending on the composition of thesupport structure22, the structural element diameter may be selected to facilitate a desired conformability and/or radial force against the renal artery when expanded. For example, asupport structure22 formed from a stiffer material (e.g., metal) may be thinner relative to asupport structure22 formed from a highly flexible polymer to achieve similar flexibilities and radial force profiles. The outward pressure of thehelical support structure22 may be assessed in vivo by an associated pressure transducer.
• In addition, certain secondary processes, including heat treating and annealing may harden or soften the fiber material to affect strength and stiffness. In particular, for shape-memory alloys such as nitinol, these secondary processes may be varied to give the same starting material different final properties. For example, the elastic range or softness may be increased to impart improved flexibility. The secondary processing of shape memory alloys influences the transition temperature, i.e., the temperature at which the structure exhibits a desired radial strength and stiffness. In embodiments that employ shape memory properties, such as shape memory nitinol, this transition temperature may be set at normal body temperature (e.g., around 37° C.) or in a range between about 37° C. and 45° C. In other embodiments that comprise super elastic nitinol, a transition temperature can be well below body temperature, for example below 0° C. Alternatively, the helical structure may be formed from an elastic or super elastic material such as nitinol that is thermally engineered into a desired helical shape. Alternatively, thehelical structure22 may be formed from multiple materials such as one or more polymers and metals.
• Referring back toFIGS. 3B and 3C together, it should be understood that thesupport structure22 of thetreatment assembly21, when not inserted into a patient, is capable of deploying to a maximum diameter that is larger than the diameter in its delivery state. Further, the helically-shapedstructure22 may be sized so that the maximum diameter is larger than the lumen diameter52 of the renal artery RA. When inserted into a patient and transformed to the deployed state, however, the helically-shapedstructure22 expands radially to span the renal artery lumen and, at its largest circumferential section, is approximately or slightly less than (e.g., in embodiments in which theenergy delivery elements24 fill some of the space) the diameter52 of the renal artery RA. A slight amount of vessel distension may be caused without undue injury and thestructure22 may expand such that its largest circumferential section is slightly more than the diameter52 of the renal artery RA, or such that one or moreenergy delivery elements24 are slightly pressed into thewall55 of the renal artery RA. A helically-shaped assembly or array that causes slight and non-injurious distension of anartery wall55 may advantageously provide stable contact force between theenergy delivery elements24 and theartery wall55 and/or hold theenergy delivery elements24 in place even as the artery moves with respiratory motion and pulsing blood flow. Because this diameter52 of the renal artery RA varies from patient to patient, thetreatment assembly21 may be capable of assuming a range of diameters between the delivery diameter and the maximum diameter.
• As provided above, one feature of the deployedtherapeutic assembly21 in the helical configuration is that theenergy delivery elements24 associated with the helical structure may be placed into stable contact with a vessel wall to reliably create consistent lesions. Further, multipleenergy delivery elements24 may be placed along the helical structure with appropriate spacing to achieve a desired lesion configuration within the target vessel. Another feature of several embodiments of thetherapeutic assembly21 having the helical configuration described above is that the assembly may be expanded to fit within a relatively wide range of different vessel diameters and/or with various tortuosities.
• B. Size and Configuration of the Energy Delivery Elements
• It should be understood that the embodiments provided herein may be used in conjunction with one or moreenergy delivery elements24. As described in greater detail below, the deployed helically-shaped structure carrying theenergy delivery elements24 is configured to provide a therapeutic energy delivery to the renal artery without any repositioning. Illustrative embodiments of theenergy delivery elements24 are shown inFIGS. 5A-5D. Theenergy delivery elements24 associated with thehelical structure22 may be separate elements or may be an integral part of thehelical structure22. In some patients, it may be desirable to use the energy delivery element(s)24 to create a single lesion or multiple focal lesions that are spaced around the circumference of the renal artery. A single focal lesion with desired longitudinal and/or circumferential dimensions, one or more full-circle lesions, multiple circumferentially spaced focal lesions at a common longitudinal position, spiral-shaped lesions, interrupted spiral lesions, generally linear lesions, and/or multiple longitudinally spaced discrete focal lesions at a common circumferential position alternatively or additionally may be created. In still further embodiments, theenergy delivery elements24 may be used to create lesions having a variety of other geometric shapes or patterns.
• Depending on the size, shape, and number of theenergy delivery elements24, the formed lesions may be spaced apart around the circumference of the renal artery and the same formed lesions also may be spaced apart along the longitudinal axis of the renal artery. In particular embodiments, it is desirable for each formed lesion to cover at least 10% of the vessel circumference to increase the probability of affecting the renal plexus. Furthermore, to achieve denervation of the kidney, it is considered desirable for the formed lesion pattern, as viewed from a proximal or distal end of the vessel, to extend at least approximately all the way around the circumference of the renal artery. In other words, each formed lesion covers an arc of the circumference, and each of the lesions, as viewed from an end of the vessel, abut or overlap adjacent or other lesions in the pattern to create either an actual circumferential lesion or a virtually circumferential lesion. The formed lesions defining an actual circumferential lesion lie in a single plane perpendicular to a longitudinal axis of the renal artery. A virtually circumferential lesion is defined by multiple lesions that may not all lie in a single perpendicular plane, although more than one lesion of the pattern can be so formed. At least one of the formed lesions comprising the virtually circumferential lesion is axially spaced apart from other lesions. In a non-limiting example, a virtually circumferential lesion can comprise six lesions created in a single helical pattern along the renal artery such that each lesion spans an arc extending along at least one sixth of the vessel circumference such that the resulting pattern of lesions completely encompasses the vessel circumference when viewed from an end of the vessel. In other examples, however, a virtually circumferential lesion can comprise a different number of lesions. It is also desirable that each lesion be sufficiently deep to penetrate into and beyond the adventitia to thereby affect the renal plexus. However, lesions that are too deep (e.g., >5 mm) run the risk of interfering with non-target tissue and tissue structures (e.g., a renal vein) so a controlled depth of energy treatment is also desirable.
• As shown inFIGS. 4A and 4B,energy delivery elements24 may be distributed on thehelical structure22 in a desired arrangement. For example, the axial distances between theenergy delivery elements24 may be selected so that the edges of the lesions formed by individualenergy delivery elements24 on therenal artery wall55 are overlapping or non-overlapping. One or both of the axial distances xx or yy may be about 2 mm to about 1 cm. In a particular embodiment, the axial distances xx or yy may be in the range of about 2 mm to about 5 mm. In another embodiment, theenergy delivery elements24 may be spaced apart about 30 mm. In still another embodiment, theenergy delivery elements24 are spaced apart about 11 mm. In yet another embodiment, theenergy delivery elements24 are spaced apart about 17.5 mm. Further, the axial distance xx may be less than, about equal to, or greater than the axial distance yy.
• Spacing ofenergy delivery elements24 may be characterized by a helical length distance zz, that is, the distance between energy delivery elements along the path of thehelical structure22. The helical length distance zz may be chosen based on the size of lesions created byenergy delivery elements24 so the lesions either overlap or do not overlap. In some embodiments, theenergy delivery elements24 are both longitudinally and circumferentially offset from one another.FIG. 4C, for example, is an end view of thehelical structure22 showing the angular offset or separation of theenergy delivery elements24 from one another around the circumference of the deployedhelical structure22. In particular,energy delivery element24cis offset fromenergy delivery element24abyangle150 and offset fromenergy delivery element24bbyangle152. The offset angles may be selected such that, when energy is applied to the renal artery viaenergy delivery elements24a,24b, and24c, the lesions may or may not overlap circumferentially.
• FIG. 4D is a side view of a vessel with formedlesions340 that circumferentially and/or longitudinally overlap, but do not overlap along a helical path. More specifically,lesions340 can be formed byenergy delivery elements24 to have a circumferential overlap341 as viewed from one end of the vessel (e.g.,FIG. 4C) and/or alongitudinal overlap342, but may not produce a helical length overlap, instead forming ahelical length gap343. For example,energy delivery elements24 may take the form of electrodes for applying an electrical field of RF energy to a vessel wall and be configured to produce lesions that are about 5 mm in diameter with the electrodes spaced apart by helical length distance of about 6 to 7 mm. Depending on the number and positioning of theenergy delivery elements24, a helical lesion pattern with any suitable number of turns may be formed. As such, thetreatment device12 may employ a single energy application to form a complex lesion pattern. It should be noted that the embodiments illustrated inFIGS. 4A-4C are exemplary, may be schematic in nature, may not correlate exactly to one another, and are shown only for the purposes of clarifying certain aspects of the technology. As such, the number and spacing ofenergy delivery elements24 are different in each ofFIGS. 4A-4C, and lesions formed by the illustrated embodiments may not create a sufficiently overlapping pattern to achieve a virtually circumferential lesion as described above, particularly when applying energy in only one deployment of thetreatment assembly21 without repositioning.
• Referring back toFIG. 3B, the individualenergy delivery elements24 are connected to energy generator26 (FIG. 1) and are sized and configured to contact an internal wall of the renal artery. In the illustrated embodiment, theenergy delivery element24 may be operated in a monopolar or unipolar mode. In this arrangement, a return path for the applied RF electric field is established, e.g., by an external dispersive electrode (shown aselement38 inFIGS. 1 and 2), also called an indifferent electrode or neutral electrode. The monopolar application of RF electric field energy serves to ohmically or resistively heat tissue in the vicinity of the electrode. The application of the RF electrical field thermally injures tissue. The treatment objective is to thermally induce neuromodulation (e.g., necrosis, thermal alteration or ablation) in the targeted neural fibers. The thermal injury forms a lesion in the vessel wall. Alternatively, a RF electrical field may be delivered with an oscillating or pulsed intensity that does not thermally injure the tissue whereby neuromodulation in the targeted nerves is accomplished by electrical modification of the nerve signals.
• The active surface area of theenergy delivery element24 is defined as the energy transmitting area of theelement24 that may be placed in intimate contact against tissue. Too much contact area between the energy delivery element and the vessel wall may create unduly high temperatures at or around the interface between the tissue and the energy delivery element, thereby creating excessive heat generation at this interface. This excessive heat may create a lesion that is circumferentially too large. This may also lead to undesirable thermal application to the vessel wall. In some instances, too much contact can also lead to small, shallow lesions. Too little contact between the energy delivery element and the vessel wall may result in superficial heating of the vessel wall, thereby creating a lesion that is too small (e.g., <10% of vessel circumference) and/or too shallow.
• The active surface area of contact (ASA) between theenergy delivery element24 and the inner vessel wall (e.g., renal artery wall55) has great bearing on the efficiency and control of the generation of a thermal energy field across the vessel wall to thermally affect targeted neural fibers in the renal plexus. While the ASA of the energy delivery element is important to creating lesions of desirable size and depth, the ratio between the ASA and total surface area (TSA) of theenergy delivery element24 and electrode46 is also important. The ASA to TSA ratio influences lesion formation in two ways: (1) the degree of resistive heating via the electric field, and (2) the effects of blood flow or other convective cooling elements such as injected or infused saline. For example, an RF electric field causes lesion formation via resistive heating of tissue exposed to the electric field. The higher the ASA to TSA ratio (i.e., the greater the contact between the electrode and tissue), the greater the resistive heating, e.g., the larger the lesion that is formed. As discussed in greater detail below, the flow of blood over the non-contacting portion of the electrode (TSA minus ASA) provides conductive and convective cooling of the electrode, thereby carrying excess thermal energy away from the interface between the vessel wall and electrode. If the ratio of ASA to TSA is too high (e.g., more than 50%), resistive heating of the tissue may be too aggressive and not enough excess thermal energy is being carried away, resulting in excessive heat generation and increased potential for stenotic injury, thrombus formation and undesirable lesion size. If the ratio of ASA to TSA is too low (e.g., 10%), then there is too little resistive heating of tissue, thereby resulting in superficial heating and smaller and shallower lesions. In a representative embodiment, the ASA of theenergy delivery elements24 contacting tissue may be expressed as
• 
  0.25TSA≦ASA≦0.50TSA
• An ASA to TSA ratio of over 50% may still be effective without excessive heat generation by compensating with a reduced power delivery algorithm and/or by using convective cooling of the electrode by exposing it to blood flow. As discussed further below, electrode cooling can be achieved by injecting or infusing cooling liquids such as saline (e.g., room temperature saline or chilled saline) over the electrode and into the blood stream.
• Various size constraints for anenergy delivery element24 may be imposed for clinical reasons by the maximum desired dimensions of the guide catheter, as well as by the size and anatomy of the renal artery lumen itself. In some embodiments such as those shown inFIGS. 13 and 25, the maximum outer diameter (or cross-sectional dimension for non-circular cross-section) of theenergy delivery element24 may be the largest diameter encountered along the length of theelongated shaft16 distal to thehandle assembly34. As previously discussed, for clinical reasons, the maximum outer diameter (or cross-sectional dimension) of theenergy delivery element24 is constrained by the maximum inner diameter of the guide catheter through which theelongated shaft16 is to be passed through theintravascular path14. Assuming that an 8 French guide catheter (which has an inner diameter of approximately 0.091 inch (2.31 mm)) is, from a clinical perspective, the largest desired catheter to be used to access the renal artery, and allowing for a reasonable clearance tolerance between theenergy delivery element24 and the guide catheter, the maximum diameter of the electrode46 is constrained to about 0.085 inch (2.16 mm). In the event a 6 French guide catheter is used instead of an 8 French guide catheter, then the maximum diameter of theenergy delivery element24 is constrained to about 0.070 inch (1.78 mm), e.g., about 0.050 inch (1.27 mm). In the event a 5 French guide catheter is used, then maximum diameter of theenergy delivery element24 is constrained to about 0.053 inch (1.35 mm).
• Based upon these constraints and the aforementioned power delivery considerations, theenergy delivery element24 may have an outer diameter of from about 0.049 to about 0.051 inch (1.24 mm-1.30 mm). Theenergy delivery elements24 also may have a minimum outer diameter of about 0.020 inch (0.51 mm) to provide sufficient cooling and lesion size. In some embodiments, theenergy delivery element24 may have a length of about 1 mm to about 3 mm. In some embodiments in which theenergy delivery element24 is a resistive heating element, theenergy delivery element24 have a maximum outer diameter from about 0.049 to 0.051 inch (1.24 mm-1.30 mm) and a length of about 10 mm to 30 mm. One embodiment ofenergy delivery elements24, for example, provides for a multiple array of 4-6 electrodes disposed about a support structure (e.g., a tubular structure). Theenergy delivery elements24, for example, may be gold electrodes or alternatively, platinum, platinum-iridium, or another suitable material. In one particular embodiment, the electrodes may measure about 0.030 inch ID×0.0325 OD inch×0.060 inch in length (0.76 mm×0.83 mm×1.52 mm). In still another particular embodiment, the electrodes may measure 0.029 inch ID×0.033 inch OD×0.060 inch length (0.72 mm×0.83 mm×1.52 mm). In yet another particular embodiment, the electrodes may measure 0.038 inch ID×0.042 inch OD×0.060 inch length (0.97 mm×1.07 mm×1.52 mm). Moreover, the electrodes may be appropriately electrically insulated from the support structure with the supply wire array of each of the electrodes jacketed in a polymer so as to provide for a compact packaged electrode array assembly about thesupport structure22.
• In other embodiments, the outer diameter of thetreatment device12 may be defined by the one or moreenergy delivery elements24 and may be further defined by elements such as e.g.,control wire168 as shown inFIG. 8A. For example, particular embodiments may be used with an 8 French guide catheter and may comprise energy delivery element(s)24 with a diameter between about 0.049 to 0.053 inch (1.24 mm to 1.35 mm) and a control wire with a diameter between about 0.005 to 0.015 inch (0.13 mm to 0.38 mm) in diameter. In other embodiments, however, the arrangement and/or dimensions of theenergy delivery elements24 and/or control wire may vary.
• In certain embodiments, thehelical structure22 may be formed of an electrically conductive material. For example, thehelical structure22 may be made from nitinol wire, cable, or tube. As shown inFIG. 5E, wire leads19 may connect thehelical structure22 toenergy generator26. Thehelical structure22 forms a contact region with the renal artery wall and acts as theenergy delivery element24. In this configuration, thehelical structure22 is capable of producing a continuous helical lesion. Ahelical structure22 that is configured to be anenergy delivery element24 may optionally comprisesensors33 positioned on, in, and/or proximate to thehelical structure22 and may be electrically connected to supplywires35.
• In other embodiments, the electrically conductivehelical structure22 is insulated at least in part. That is, the conductive helical structure is partially covered with an electrically insulating material and the uncovered portions of thehelical structure22 serve as one or more conductiveenergy delivery elements24. Theenergy delivery elements24 may be any size, shape, or number, and may be positioned relative to one another as provided herein.
• Energy delivery element24 may be configured to deliver thermal energy, i.e., to heat up and conduct thermal energy to tissue. For example, energy delivery elements may be an electrically resistive element such as a thermistor or a coil made from electrically resistive wire so that when electrical current is passed through the energy delivery element heat is produced. An electrically resistive wire may be for example an alloy such as nickel-chromium with a diameter for example between 48 and 30 AWG. The resistive wire may be electrically insulated for example with polyimide enamel.
• In certain embodiments, theenergy delivery elements24 may be angularly repositioned relative to the renal artery during treatment. Referring back toFIGS. 1 and 2, for example, this angular repositioning may be achieved by compressing thetherapeutic assembly21 and rotating theelongated shaft16 of thetreatment device12 via thehandle assembly34. In addition to the angular or circumferential repositioning of theenergy delivery elements24, theenergy delivery elements24 optionally may also be repositioned along the lengthwise or longitudinal dimension of the renal artery. This longitudinal repositioning may be achieved, for example, by translating theelongated shaft16 oftreatment device12 viahandle assembly34, and may occur before, after, or concurrent with angular repositioning of theenergy delivery elements24. With reference toFIG. 3B, repositioning theenergy delivery elements24 in both the longitudinal and angular dimensions places theenergy delivery elements24 in contact with theinterior wall55 of the renal artery RA at a second treatment site for treating the renal plexus RP. In operation, energy may then be delivered via theenergy delivery elements24 to form a second focal lesion at this second treatment site. For embodiments in which multipleenergy delivery elements24 are associated with the helical structure, the initial treatment may result in two or more lesions, and repositioning may allow additional lesions to be created.
• In certain embodiments, the lesions created via repositioning of the helically-shapedsupport structure22 are angularly and longitudinally offset from the initial lesion(s) about the angular and lengthwise dimensions of the renal artery RA, respectively. The composite lesion pattern created along the renal artery RA by the initial energy application and all subsequent energy applications after any repositioning of the energy delivery element(s)24 may effectively result in a discontinuous lesion (i.e., it is formed from multiple, longitudinally and angularly spaced treatment sites).
• In an alternative embodiment, theenergy delivery element24 may be in the form of an electrically conductive wire. As shown inFIG. 5D, for example, aconductive wire500 may be wound about thehelical structure22 to form a coiledelectrode24′. The coiledelectrode24′ may provide increased surface area for delivering energy. For example, the coiledelectrode24′ may form a generally continuous helical lesion in a single energy application. The coiledelectrode24′ may be wound in any manner about thehelical structure22, depending on the desired lesion. For example, the coiledelectrode24′ may form a continuous path along a length of the helix or the coiled structure may form one or more short discrete electrodes separated by non-conducting sections. In other embodiments, portions of the coiledelectrode24′ may be positioned on the helical structure to come in contact with the vessel wall when the helical structure is expanded, while other portions of the coiledelectrode24′ may be positioned away from the vessel wall when the helical structure is expanded to allow lesions to be discontinuous. Further, in such an arrangement, regions of the coiledelectrode24′ that do not contact the renal artery may contribute to cooling of theenergy delivery elements24′, as described in greater detail below. The positioning and number of conductive portions forming theenergy delivery elements24′ may be selected according to a desired lesion pattern.
• In the embodiments shown inFIGS. 5A and 5B,energy delivery elements24 preferably comprise metal electrodes with rounded ends and a lumen. The nitinolhelical support structure22 is preferably electrically insulated (e.g., with PET) and theelectrodes24 are mounted over the insulation.Supply wires25 connect the electrodes to an energy source (not shown) and deliver energy (e.g., RF electrical current) to theelectrodes24. The rounded ends reduce mechanical irritation to the vessel wall and provide a more consistent current density when energy is delivered compared to electrodes with square or sharper ends. Theenergy delivery elements24 may alternatively comprise other forms as noted, such as acoil electrode24′ described above with reference toFIG. 5D. In another embodiment, thestructural element510 that forms thehelical structure22 may be theenergy delivery element24′ itself, as seen, for example inFIG. 5C.
III. SELECTED EMBODIMENTS OF RENAL DENERVATION SYSTEMS
• The representative embodiments provided herein include features that may be combined with one another and with the features of other disclosed embodiments. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions should be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another.
• FIG. 6A illustrates an embodiment of atreatment device112 including anelongated shaft116 having different mechanical and functional regions configured in accordance with an embodiment of the technology. Theelongated shaft116 of thetreatment device112, for example, includes a distal region with a therapeutic ortreatment assembly121 for delivery and deployment at a renal artery site for treatment and, in particular, for renal denervation. Disposed at a proximal end of theelongated shaft116 is ahandle assembly134 for manipulation of theelongated shaft116 and thetherapeutic assembly121. More specifically, thehandle assembly134 is configured with an actuator136 (schematically shown) to provide for remote operation of a control member (e.g.,control wire168 ofFIG. 6E or8A) for controlling or transforming thetherapeutic assembly121 between a delivery state and a deployed state. Further details regarding suitable handle assemblies may be found, for example, in U.S. patent application Ser. No. 12/759,641, “Handle Assemblies for Intravascular Treatment Devices and Associated System sand Methods” to Clark et al., which is incorporated herein by reference in its entirety.
• Thetreatment device112 is configured to deliver thetherapeutic assembly121 to a treatment site in a delivery (e.g., low-profile) state in which theassembly121 is substantially linear (e.g., straight) such that energy delivery elements (not shown) carried by asupport structure122 of thetreatment assembly121 are substantially axially aligned along thesupport member122. Once located at the treatment site within the renal artery, thehandle assembly134 is operated for actuation of a control member that transforms thetherapeutic assembly121 from the delivery state to a deployed state. In one embodiment, for example, the control member comprises a control wire168 (FIG. 8A) disposed within an internal lumen of thetubular support structure122. One end of thecontrol wire168 may be affixed at or near the distal end of thesupport structure122, and the opposite end of thecontrol wire168 terminates within thehandle assembly134. As mentioned previously, thehandle assembly134 is configured for manipulating thecontrol wire168 to transform thetherapeutic assembly121 between the delivery and the deployed states. The tension in thecontrol wire168 provides for a proximally and axially directed force that acts on thesupport structure122. Under the influence of the tension force in thecontrol wire168 and, in operation within a patient under the influence of a radial constraint of the patient's renal arterial wall, thesupport structure122 deforms so as to deploy into the helical geometry to bring the energy delivery elements into stable contact with the wall of the renal artery.
• To provide for the desired deformation upon deployment, thesupport structure122 may be a tubular member having a plurality of slots, cuts, through holes, and/or openings selectively formed or disposed about thesupport structure122. Thetubular support structure122 may have a number of features generally similar to the features ofsupport structure22 described above. For example, thesupport structure122 may be formed from biocompatible metals and/or polymers, including PET, polyamide, polyimide, polyethylene block amide copolymer, polypropylene, or PEEK polymers, and the slots are preferably laser cut into the tubular structure in a desired configuration. In particular embodiments, thesupport structure122 may be electrically nonconductive, electrically conductive (e.g., stainless steel, nitinol, silver, platinum nickel-cobalt-chromium-molybdenum alloy), or a combination of electrically conductive and nonconductive materials. In one particular embodiment, thesupport structure122 may be formed of a pre-shaped material, such as spring temper stainless steel or nitinol. Moreover, in some embodiments thesupport structure122 may be formed, at least in part, from radiopaque materials that are capable of being imaged fluoroscopically to allow a clinician to determine if thesupport structure122 is appropriately placed and/or deployed in the renal artery. Radiopaque materials may include barium sulfate, bismuth trioxide, bismuth subcarbonate, powdered tungsten, powdered tantalum, or various formulations of certain metals, including gold, platinum, and platinum-iridium, and these materials may be directly incorporated into thesupport structure122 or may form a partial or complete coating of thesupport structure122.
• The location, orientation and/or configuration of the slots, cuts, through holes, and/or openings formed or disposed about thesupport structure122 define the deformation of the structure. Moreover, the slots, cuts, through holes, and/or openings can be varied along thetubular structure122 so as to define varying regions of deformation along the structure. In the embodiment illustrated inFIG. 6A, for example, thetubular structure122 includes adistal deflection region122a, anintermediate orientation region122bproximal to thedistal deflection region122a, and a transition orflexible region122cproximal to theorientation region122b. As will be described in greater detail below, thedeflection region122ais configured to have a substantially helical geometry upon deployment. Theorientation region122bis configured to locate or bias thedeflection region122aaway from a longitudinal axis B of theelongated shaft116 and toward a wall of the renal artery. Thetransition region122cis configured to provide flexibility to thetreatment device112 as theelongated shaft112 is advanced through the sometimes tortuous intravascular path from the percutaneous access site to the targeted treatment site within the respective renal artery (as described above with reference toFIG. 2). Further details regarding various mechanical and functional aspects of the different regions of thetreatment device112 are described below.
• FIG. 6B is a plan view of a slot pattern configured in accordance with one embodiment of the technology. Referring toFIGS. 6A and 6B together, for example, thedeflection region122amay be defined by a plurality of substantially equal lengthtransverse slots128 arranged along thesupport structure122 in a spiral fashion. Theorientation region122bmay be defined by a plurality of axially spacedtransverse slots130 in which at least two slots differ in length. Further, as best seen inFIG. 6A, theorientation region122bcan have a smaller axial length than thedeflection region122a. Thetransition region122cis located proximally of theorientation region122band has an axial length greater than each of thedeflection region122aand theorientation region122b. In the illustrated embodiment, thetransition region122ccan include a continuous spiral cut or slit132 having a varying pitch along thesupport structure122. In one embodiment, for example, the pitch of the spiral cut132 can increase proximally along theelongated shaft116. Further details regarding various mechanical and functional aspects of the regions of thetreatment device112 are described below.
• FIG. 6C is a perspective view of thetreatment device112 including thesupport structure122 in a delivery state (e.g., low-profile or collapsed configuration) outside of a patient in accordance with an embodiment of the present technology, andFIG. 6D is a perspective view of thesupport structure122 in a deployed state (e.g., expanded configuration). For ease of understanding, thesupport structure122 inFIGS. 6C and 6D is shown without energy delivery elements disposed about thesupport structure122.
• Referring toFIGS. 6C and 6D together, thesupport structure122 comprises a tubular member having a central lumen to define a longitudinal axis B-B. As described above, thesupport structure122 includes a proximal generallyflexible transition region122c, anintermediate orientation region122b, and adistal deflection region122a. Thesupport structure122 is selectively transformable between the delivery state (FIG. 6C) and the deployed state (FIG. 6D) by application of a force having at least a proximally directed axial component and preferably applied at or near thedistal end126ato transformdistal deflection region122aandintermediate orientation region122b. In one embodiment, for example, an axial force applied at or near thedistal end126adirected at least partially in the proximal direction deflects thedistal deflection region122aof thesupport structure122 such that it forms the helically-shaped support structure such as is shown inFIG. 6D (e.g., within the renal artery) to bring one or more energy delivery elements (not shown) into contact with the inner wall of the renal artery.
• The Deflection Region
• As mentioned above, to provide thesupport structure122 with the desired deflection and deployment configuration, thedeflection region122aincludes a plurality ofslots128a,128b,128c, . . .128n. Again, the plurality ofslots128a-128nare selectively formed, spaced, and/or oriented about the longitudinal axis B-B such that thedistal deflection region122adeflects in a predictable manner to form a helical geometry in the deployed state within the renal artery. Outside of the renal artery or other lumen that may radially constrain deflection of thedistal region122a, thedistal region122amay define a non-helical geometry in its fully expanded configuration, such as, for example, a substantially circular geometry as shown inFIG. 6E. As shown therein, thecontrol wire168 is disposed in the central lumen of thesupport structure122, and is anchored at or near thedistal end126a. When thecontrol wire168 is placed under tension in the proximal direction, at least a portion of thedeflection region122a(in the absence of any restriction in the radial direction) deflects from the substantially straight shape ofFIG. 6C to form the substantial circular shape ofFIG. 6E. More specifically, referring toFIGS. 6C-6E together, a portion of thedeflection region122adeflects such that thedeflection slots128a-ndeform and close or approximately close (as shown schematically inFIG. 6E) and provide contact between the edges of thesupport structure122 framing a central region in eachslot128. Further details regarding the configuration of the slots are described below.
• Thedeflection region122ais arranged to deflect about a center of curvature Z to define a first radius of curvature r with respect to afirst surface122dof thesupport member122, and a second radius of curvature R with respect to asecond surface122e. The second radius of curvature R is greater than the first radius of curvature r with the difference being the width or diameter d of thesupport member122 measured at its outer surface. Under a radial constraint of, for example, the inner wall of a renal artery, thedeflection region122adeforms to define a substantially helical deployed shape (as depicted inFIG. 6D) instead of the substantial circular shape defined in the absence of radial constraint (as depicted inFIG. 6E). Thus, the proportions of the substantially helical deployed shape (e.g., the diameter and pitch of the helix) can vary according to the inner diameter of the lumen (e.g., the renal artery lumen) within which thedeflection region122ais deformed.
• The arrangement and configuration of theslots128a-128n(FIG. 6C) further define the geometry of the deflectabledistal region122a.FIG. 6F, for example, schematically illustrates a slot pattern forslots128 in accordance with one embodiment of the technology to illustrate the slot spacing and orientation about thedeflection region122aof thesupport member122. Although only fourslots128a-dare shown inFIG. 6F, it will be appreciated that thedeflection region122acan have any number of desiredslots128. Referring toFIGS. 6E and 6F together, the centers of theslots128 are disposed and spaced along a progressive axis C-C. The progressive axis C-C defines a progressive angle θ with the longitudinal axis B-B of the support structure122 (FIG. 6A) to define an angular spacing of y about the center of curvature Z (FIG. 6E) in the unconstrained deployed state. The centers of theslots128a-128dare shown as substantially equidistantly spaced at a distance x. Alternatively, however, the center spacing between the slots may vary (x1, x2, etc.) along the progressive axis C-C. Eachslot128 further defines a maximum arc length L about the longitudinal axis B-B and a maximum slot width W in the direction of the longitudinal axis B-B.
• The total number ofslots128 in theregion122aunder deflection multiplied by the slot width W populated in a specific length defines the first radius of curvature r in the deflected portion of thedeflection region122a(when placed in an unconstrained deployed state). In one particular embodiment, for example, each slot ma have a width W ranging from about 0.0005 to 0.010 inch (0.01 to 0.25 mm) and a slot arc length L of about 0.0005 to 0.010 inch (0.01 to 0.25 mm) so as to define a first radius of curvature r in an unconstrained deflected state that ranges between about 3.5 to 6 mm (7 to 12 mm diameter). Minimizing the first radius of curvature r at a maximum application of axial force through thedeflection region122aof thesupport member122 defines the flexibility of thedeflection region122a. Accordingly, the smaller the first radius of curvature r, the greater the flexibility; the greater the first radius of curvature r, the greater the stiffness. Thus, the flexibility and/or stiffness of thedeflection region122aof thesupport member122 can be defined by selecting the number and/or width of slots of thedistal region122a. In one embodiment, for example, thedeflection region122acan include approximately 2 to 100 slots, with each having a slot width W ranging from about 0.0005 to 0.010 inch (0.01 to 0.25 mm) and a slot arc length L of about 0.0005 to 0.010 inch (0.01 to 0.25 mm) so as to define a first radius of curvature r in an unconstrained deflected state that ranges between about 3.5 to 6 mm (7 to 12 mm diameter).
• Because the first radius of curvature r of thedeflection region122ais directly related to the number ofslots128, the number ofslots128 can be few in number so as to provide for a non-continuous radius of curvature in a segment of thedeflection region122asuch that the segment is substantially polygonal.FIG. 6G, for example, is a schematic plan view of atreatment device112′ configured in accordance with another embodiment of the technology. Adeflection region122′aof thetreatment device112′ may include a low or reduced number of deflection slots128 (e.g., threeslots128a-care shown) such that thedeflection region122′adefines a substantially polygonal geometry when under a tension load at its distal end (i.e., from control wire168). In other embodiments, a different number ofslots128 may be used to selectively form a desired geometry for thetreatment device112′.
• Referring back toFIGS. 6B and 6C and as noted previously, thedeflection region122ais defined by a plurality ofdeflection slots128 in which eachslot128 extends substantially transverse to the longitudinal axis B-B of thesupport structure122 with theslots128 being of substantially similar arc length. Moreover, with reference toFIG. 6F, the centers of theslots128 of thedeflection region122aare generally spaced apart along a progressive axis CC that is skewed from the longitudinal axis BB such that theslots128 of thedeflection region122aprogress in a generally spiral fashion along thesupport structure122 in the axial direction (as best seen inFIG. 6C). The plurality ofslots128 of thedeflection region122aare selectively formed, spaced, and/or oriented about the longitudinal axis B-B such that thedeflection region122adeflects or deforms in a predictable manner so as to preferably form a helical geometry when in a deployed state (e.g., within the renal artery).
• Referring again toFIG. 6B, for example, thedeflection region122aincludes a pattern ofdeflection slots128 arranged in accordance with one embodiment of the technology to illustrate the slot spacing and orientation about the support member122 (FIG. 6A). The centers of thedeflection slots128 are disposed and spaced along progressive axis C-C. The progressive axis C-C defines a progressive angle θ₁with the longitudinal axis B-B of the support structure122 (FIG. 6A). The progressive angle θ₁defines and, more particularly, directly corresponds to a pitch angle of the helical geometry defined by thesupport structure122 when in a deployed state. The progressive angle θ₁can range from, for example, about zero degrees (0°) to about six degrees (6°), e.g., one-half degree, (0.5°), two degrees (2°), etc. The centers of thedeflection slots128 are shown as substantially equidistantly spaced apart. In other embodiments, however, the center spacing betweenslots128 may vary along the progressive axis C-C. The total number ofslots128 defining thedeflection region122acan be from about 2 to 100 slots (e.g., about 80 slots). In one particular embodiment, the total axial length of thedeflection region122ais about one inch (2.54 cm). In other embodiments, however, thedeflection region122acan have a different number ofslots128 and/or the slots can have different dimensions or arrangements relative to each other.
• In one embodiment, each of thedeflection slots128 comprises a substantially rectangularcentral region129athat extends generally perpendicular to and about the central longitudinal axis B-B of theshaft116. The elongate lateral walls of thecentral region129adefine a slot width W therebetween (e.g., about 0.0015 inch (0.038 mm)) to define a maximum gap that may be closed when theslot128 deforms during deflection ofregion122a. Eachslot128 further compriseslateral regions129bin communication or contiguous with thecentral region129a. In one embodiment, thelateral regions129bare substantially circular and have a diameter (e.g., 0.0060 inch (0.15 mm)) to define regions for stress relief at the ends ofslots128. The spacing between the centers of the substantially circularlateral regions129bdefine an arc length L (e.g., about 0.040 inch (1.02 mm)) about the longitudinal axis of thestructure122. In some embodiments, theselateral regions129bmay be formed as elliptical cuts on a non-perpendicular angle relative to the longitudinal axis B-B of thesupport structure122,122′,122″.
• Alternate configurations of the deflection slots are possible. For example, the deflection slots can be more specifically formed to provide a desired flexibility and deflection in thedeflection region122aof thesupport member122.FIGS. 6H and 6I, for example, illustrate adeflection region122a″ havingdeflection slots128′ configured in accordance with another embodiment of the technology. In this embodiment, thedeflection slots128′ extend substantially transverse to the progressive axis C-C and are substantially symmetrical about the progressive axis C-C. Theslots128′, for example, can be generally “I-shaped” and include acentral region129aextending perpendicular to the progressive axis C-C with two enlargedlateral regions129bdisposed about thecentral slot region129a. Further, the walls of thesupport structure122″ forming the perimeter of each of thelateral regions129bdefine a substantially rectangular geometry preferably extending substantially parallel to the longitudinal axis B-B of thesupport structure122″ with the corners of the rectangular-shaped openings being radiused. Thecentral region129aof theslots128′ can include a substantially circular cut-outregion129cformed in communication with thelateral regions129b. Alternatively, in some embodiments thecentral region129cof theslots128′ may be generally rectangular and not include a circular cut-out.
• As best seen inFIG. 6I, thedistal slots128′ extend about the longitudinal axis B-B of thesupport structure122″ at an arc length L′ of, for example, less than about 0.05 inch (1.27 mm), e.g., about 0.04 inch (1.02 mm). Thelateral regions129bdefine the maximum width W′ of thedeflection slot128′ to be, for example, about 0.03 inch (0.76 mm). Thecircular portion129cofcentral region129ais contiguous with or in communication with the lateral regions and includes a central circular cut-out129chaving a diameter of e.g., about 0.01 inch (0.25 mm). Thecentral region129adefines a minimum width of, e.g., about 0.02 inch (0.51 mm) in the longitudinal direction of the support structure. In one particular embodiment, the total number ofslots128′ in the distal region is less than 30 slots (e.g., 25 slots), the slot spacing is about 0.03-0.04 inch (0.76-1.02 mm), and the slots are equally spaced apart in thedistal deflection region122″. In other embodiments, however, the distal region may have a different number of slots and/or the slots may have a different arrangement (e.g., different dimensions, different or non-equal spacing between slots, etc.).
• Alternate slot, cut, and/or opening configurations can provide desired flexibility, stress-relief or other performance characteristics.FIG. 6J, for example, is analternative slot arrangement128″ that can be used, for example, in either thedeflection region122aor theorientation region122b(described in greater detail below) of thesupport structure122. Theillustrative slot128″ includes a central region129′athat extends substantially perpendicular and about the longitudinal axis B-B of thesupport structure122. The opposed lateral walls of the central region129′aare generally arcuate, each defining a radius of curvature (e.g., about 0.06 inch (1.52 mm)) with a maximum gap WWW therebetween (e.g., about 0.005 inch (0.13 mm)) to define the maximum slot gap that may be partially or fully closed during deflection of thesupport structure122. Further, disposed about the longitudinal axis B-B of thesupport structure122 are lateral regions129′bin communication or contiguous with the central region129′a. The lateral regions129′bare substantially circular and each have a diameter (e.g., 0.005 inch (0.13 mm)) to define regions for stress relief. The spacing between the centers of the curved lateral regions129′bdefine a length LLL (e.g., about 0.04 inch (1.02 mm)) about the longitudinal axis B-B of thesupport structure122. These lateral regions129′bmay be formed, for example as elliptical cuts on a non-perpendicular angle relative to a longitudinal axis of the shaft.
• The configuration of a slot in thedeflection region122aand/ororientation region122bof the elongated shaft can impact the flexibility of thesupport structure122. For example, as shown inFIGS. 6K and 6L, the inclusion (or absence) of the circular cut-out129cin thecentral region129aof aslot128,128′,128″ can vary the number of contact points between the sidewalls of the slots disposed about the bisecting axis of the slot.FIG. 6K, for example, illustrates a portion of thedistal region122a″ in a deflected or bent configuration. The central circular cut-out129cprovides for twocontact points602 between the sidewalls ofcentral region129a—one point of contact between each of thelateral regions129band the central circular cut-out129c. In contrast and with reference toFIG. 6L, the absence of a central circular cut-out129cprovides for asingle contact point602 between the walls of thecentral region129cwhen along a deflected portion of thedistal region122″.
• It should also be noted that, in order to facilitate fabrication of thesupport members122,122′,122″, thedeflection slots128,128′,128″ described above may be formed perpendicular or generally perpendicular to either the longitudinal axis B-B or the progressive axis C-C without impairing the ability of thesupport member122,122′,122″ to form the desired helical geometry when in a deployed state.
• Further, as described above with reference toFIG. 6E, whensupport structure122 is transformed from the delivery state to the deployed state,slots128,128″,128′″ are deformed such that the walls definingcentral regions129a,129″a(as shown, for example, inFIGS. 6B,6I, and6J) approach each other to narrow the corresponding gap widths W, WW, WWW up to and including fully closing the gap wherein one or more pairs of opposing contact points touch each other (as shown schematically inFIG. 6E and described above with reference toFIGS. 6K and 6L).
• The Orientation Region
• Referring back again toFIGS. 6A-6D and as discussed previously, disposed proximally of thedeflection region122ais theorientation region122bdefined by a plurality oforientation slots130. It may be desirable to control the orientation of the helical axis relative to the longitudinal axis B-B of thesupport structure122. For example, in a therapeutic assembly incorporating thesupport structure122, it may be desirable to direct the therapeutic assembly in a selected direction away from the longitudinal axis B-B such that at least a portion of thedeflection region122ais laterally off-set from theproximal end126bof thesupport structure122 and/or a distal end of theelongated shaft116. As best seen inFIG. 6D, for example, theorientation region122bcan include orientation slots oropenings130 that are formed, spaced and/or oriented to provide for an orientation axis B-B that is skewed (e.g., from about 45 degrees (45°) to about 90 degrees (90°)) relative to the longitudinal axis B-B and orients the helically shaped geometry of thedeflection region122aadjacent the renal artery wall with the helical axis directed axially along the renal artery.
• Theorientation slots130 can have a variety of different arrangements/configurations. Referring toFIG. 6B (and with reference toFIG. 6M), for example, the centers oforientation slots130 are disposed and spaced along an orientation axis D-D that is radially offset from the progressive axis C-C (e.g., by about 90° about the longitudinal axis B-B of the support structure122). The orientation axis D-D may extend generally parallel to the longitudinal axis B-B or, alternatively, may be skewed at a selected angle relative to the longitudinal axis B-B (as described in greater detail below with reference toFIG. 6N). In the illustrated embodiment, the centers of theorientation slots130 are shown as substantially equidistantly spaced apart. In other embodiments, however, the spacing between theindividual slots130 may vary along the orientation axis D-D. Eachslot130 defines a maximum arc length LL about the longitudinal axis B-B and a maximum slot width WW in the direction of the longitudinal axis B-B.
• Referring toFIG. 6B, in one embodiment theorientation slots130 can include groups of slots of varying arc length LL about the longitudinal axis B-B. For example, theorientation slots130 can include a first group oforientation slots130ahaving a first arc length, a second group oforientation slots130bhaving a second arc length less than the first arc length of the first group oforientation slots130a, and a third group oforientation slots130chaving a third arc length less than the second arc length ofgroup130b. For example, in one particular embodiment, the first group oforientation slots130ahas an arc length of about 0.038 inch (0.97 mm), the second group oforientation slots130bhas an arc length of about 0.034 inch (0.86 mm), and the third group oforientation slots130chas an arc length of about 0.03 inch (0.76 mm). In other embodiments, however, theorientation slots130 may have different sizes and/or arrangements relative to each other. For example, in some embodiments one or more groups oforientation slots130 may have different slot widths (in addition to, or in lieu of, varying arc lengths).
• In one embodiment, the total number ofslots130 defining theorientation region122bis less than 20 slots (e.g., about 5 to 15 slots, about 6 to 12 slots, etc.) equally spaced over theorientation region122b. Further, in one particular embodiment, the total axial length of theorientation region122bis about 0.2 to 0.25 inch (5.08 to 6.35 mm). In other embodiments, theorientation region122bmay have a different number of slots and/or a different arrangement and/or dimensions.
• Alternate configurations of the orientation slots are possible. For example, Referring back again to the pattern illustrated inFIG. 6I,orientation slots130′ may be substantially elongated defining a preferably maximum arc length LL′ about the longitudinal axis B-B and a maximum slot width WW in the direction of the longitudinal axis B-B. In one particular embodiment, for example, eachorientation slot130′ has a width W′ ranging from about 0.0005 to 0.010 inch (0.01 mm to 0.03 mm) and a slot arc length LL′ of about 0.0005 to 0.010 inch (0.01 mm to 0.03 mm) so as to define a first radius of curvature r in an unconstrained deflected state that ranges between about 7 to 12 mm. In other embodiments, however, theorientation slots130′ may have other dimensions and/or arrangements.
• In the illustrated embodiment, theorientation slots130′ extend generally perpendicular to the orientation axis D-D and are substantially symmetrical about the orientation axis D-D. Theorientation slots130′ are generally “I-shaped” having acentral region131aextending perpendicular to the orientation axis D-D with two enlargedlateral regions131bdisposed about thecentral slot region131afor stress relief. In this embodiment, the walls of thesupport structure122″ forming the perimeter of each of thelateral regions131bcan define, for example, a substantially rectangular geometry extending substantially parallel to the longitudinal axis B-B of thesupport structure122″ with the corners of the rectangular-shaped openings being radiused (not shown). Further,central regions131aof theindividual orientation slots130′ may be generally rectangular, or may have another suitable shape.
• Each of theorientation slots130′ depicted inFIG. 6I can include a substantial rectangularcentral region131athat extends substantially perpendicular and about the longitudinal axis B-B of thesupport structure122. The elongate lateral walls of thecentral region131adefine a gap therebetween (e.g., about 0.0015 inch (0.038 mm)) to define the maximum closing gap of the slot during deflection of thestructure122. Eachslot130′ can also includelateral regions131bdisposed about the longitudinal axis B-B and in communication or contiguous with thecentral region131a. Thelateral regions131bdefine a substantially rectangular geometry preferably extending substantially parallel to the longitudinal axis B-B of thesupport structure122″ with the corners of the rectangular-shaped openings being radiused to define regions for stress relief. The spacing between the centers of the substantially rectangularlateral regions131bdefine an arc length L (e.g., about 0.04 inch (1.02 mm)) about the longitudinal axis B-B of thesupport structure122″. Alternatively,lateral regions131bmay be formed as elliptical cuts on a non-perpendicular angle relative to the longitudinal axis B-B of thesupport structure122,122′,122″.
• In some embodiments, the total number ofslots130′ in the orientation region is generally less than ten slots, e.g., five slots, the slot spacing can be, e.g., about 0.03 to 0.04 inch (0.76 mm to 1.02 mm), and theslots130′ can be equally spaced apart. Further, in some embodiments the orientation axis D-D can be generally parallel to the longitudinal axis B-B and radially offset from the progressive axis C-C at a minimum arc length distance of, e.g., about 0.01 inch (0.25 mm) over an angle ranging from about 50° to less than 90° about the longitudinal axis B-B of thesupport structure122″.
• In yet another embodiment, theorientation slots130 may be disposed along an orientation axis that is substantially skewed with respect to the longitudinal axis B-B.FIG. 6N, for example, is a plan view of a slot pattern configured in accordance with another embodiment of the technology. In this embodiment, theorientation slots130 are disposed on an orientation axis D₂-D₂that may be skewed relative to the longitudinal axis B-B by an angle θ₂ranging from, e.g., about 0 degrees (0°) to about 45 degrees (45°). The angled orientation axis D₂-D₂provides for anorientation region122bhaving a tapered helical geometry upon deployment of thesupport structure122.FIG. 6O, for example, is a schematic illustration of a portion of a treatment device having a support structure including the slot pattern ofFIG. 6N in a deployed state within a renal artery of a patient.
• The Flexible/Transition Region
• Referring again toFIG. 6A, disposed proximally of theorientation region122bis the flexible ortransition region122c. As noted above, theflexible region122ccan include, for example, the transitional helical or spiral slit or cut132 having a variable pitch over its length. The variable pitch of the spiral cut132 along the length of theflexible region122cprovides thesupport structure122 with variable flexibility along the length of theelongated shaft116. In one embodiment, for example, thetransitional cut132 extends over an axial length of, e.g., about 170 mm initiating proximal to theorientation region122b. In other embodiments, however, thetransitional cut132 may have a different length.
• As illustrated inFIGS. 6C and 6D, in some embodiments the pitch of the transition cut132 may vary over the length of the transition cut to define multiple, different transition regions (fourtransition regions132a,132b,132c, and132dare shown inFIG. 6C). More specifically, in one embodiment, thecut132 defines a firsttransitional portion132ahaving a first pitch by forming, e.g., five revolutions about thetubular support structure122 at a spacing of 0.02 inch (0.51 mm) and transitions to a secondtransitional portion132bhaving a second pitch defined by, e.g., five revolutions at a spacing of 0.040 inch (1.02 mm). Thecut132 continues to define a thirdtransitional portion132ahaving a third pitch defined by, e.g., ten revolutions at a spacing of 0.06 inch (1.52 mm) and transitions to a fourth pitch defined by, e.g., twenty revolutions at a spacing of 0.08 inch (2.03 mm). It should be appreciated in the above example that, considering each sequentialtransitional portion132 in order from the distal end to the proximal end oftransition region122c, the slit pitch spacing increases and the flexibility oftubular support structure122 decreases.
• Thetransitional cut132 may have a generally constant width of, e.g., about 0.0005 inch (0.01 mm) over its length, or the width of thetransitional cut132 may vary over its length. Thetransitional cut132 can also include at each end a substantially circular void contiguous with or in communication with the transitional cut. In other embodiments, however, thetransitional cut132 can have a different arrangement and/or different dimensions. For example, rather than having stepwise increases in pitch, thetransitional cut132 may have a continuously increasing pitch from the distal end to the proximal end oftransition region122c.
• Alternate slot, cut and/or opening configurations can provide for the desired flexibility, stress-relief or other performance characteristics in theflexible region122cin lieu of the transition cut132. In some embodiments, for example, opening or apertures may be selectively formed in theelongated shaft116 to provide the desired flexibility. The individual openings or apertures of theflexible region122ccan, for example, have centers disposed along an axis that extends parallel to the central longitudinal axis B-B of thesupport structure122.FIGS. 7A and 7B, for example, illustrate thesupport structure122 with an alternate arrangement for theflexible region122c, having through holes oropenings132′a,132′b,132′cthat each extend through thetubular support structure122. Theopenings132′, for example, can be alternately disposed on axes that are angularly spaced from one another about the longitudinal axis B-B of thesupport structure122. In the illustrated embodiment, for example, opening132′bis angularly disposed at 90° relative to the axiallyadjacent openings132′aand132′c. In other embodiments, however, theopenings132′ may have a different arrangement.
• FIG. 8A is a broken perspective view in partial section of atreatment device100 including a catheter having anelongated shaft116 with adistal region120 having asupport structure122 for delivery and deployment of a therapeutic ortreatment assembly121 at a target treatment site in a lumen and, in particular, for performing renal denervation within a renal artery. Disposed at a proximal end of theelongated shaft116 is ahandle assembly134, shown schematically, for manipulation of theelongated shaft116 and thetherapeutic assembly121. More specifically, thehandle assembly134 is configured to provide for remote operation of a control member168 (e.g., a control wire) for controlling or transforming thetherapeutic assembly121 between a delivery state and a deployed state (shown inFIG. 8A).
• Thesystem100 is configured to deliver thetherapeutic assembly121 to the treatment site in a delivery state (not shown) in which thetherapeutic assembly121 is substantially linear (e.g., straight) such that theenergy delivery elements124 are substantially axially aligned along thesupport member122.Energy supply wires25 may be disposed along an outer surface of thesupport member122 and coupled to each of theenergy delivery elements124 for supplying treatment energy to the respectiveenergy delivery elements124. Once located at the treatment site within the renal artery, actuation of thecontrol member168 that transforms thetherapeutic assembly121 from the delivery state to the deployed state as shown. In the illustrated embodiment, thecontrol wire168 is disposed within thetubular support structure122. One end of thecontrol member168 may be affixed at or near thedistal end126aof the support structure122 (e.g., terminating in a tip member174). The opposite end of thecontrol member168 can terminate within thehandle assembly134 and be operably coupled to an actuator for transforming thetherapeutic assembly121 between the delivery and the deployed state.
• The tension in thecontrol member168 can provide a proximal and/or axially directed force to thedistal end126aof thesupport structure122. For example, under the influence of the tension force in thecontrol member168, thedistal region122bof thesupport structure122 deflects. Thedistal deflection region122apreferably include a plurality of slots128 (only two are shown as128′aand128′b). As described above, theslots128′aand128′bare disposed along a progressive axis. Theslots128′aand128′bformed in thedistal region122aof the support structure bias the deflection of thedistal region122aso as to form one or more curved portions, each having a radius of curvature preferably defined by the number ofdeflection slots128, the individual slot width, slot configuration, and/or slot arrangement. As thedistal region122acontinues to deflect, it radially expands placing one or more of the spaced-apartenergy elements124 into contact with theinner wall55 of the renal artery. Thesupport structure122, when subject to the tension of thecontrol wire168 and the radial constraints of thevessel wall55, is configured to form a substantially helical shape so as to axially space and radially offset theenergy delivery elements124 from one another. Moreover, because thedeflection region122aof thesupport structure122 is configured to form a helical geometry within the renal artery when under a tension load, thetreatment assembly121 is not expected to radially overload thewall55 of the renal artery. Rather, thesupport structure122 deforms to form the helix under a continuously increasing tension load.
• As discussed above, the progressive angle of the axis (e.g., progressive axis C-C) along which thedeflection slots128,128′,128″ are disposed defines the helical angle of the resulting deployed arrangement. In one embodiment, an amount of tension to fully deploy thetherapeutic assembly121 is typically less than, for example, about 1.5 lbf (pound-force) (0.68 kgF) applied at thedistal end126aof thetherapeutic assembly121, e.g., between about 1 lbf (0.45 kgF) to about 1.5 lbf (0.68 kgF). In the helically shaped deployed state ofFIG. 8A, theslots128′ are disposed along the interior surface of the helix with thesupply wires25 for theenergy delivery elements24 disposed on an outer surface of the helix so as to form a “spine” of the assembly. Thesupply wires25 can extend along the length of thetreatment device112 to an appropriately configured energy generator (not shown).
• Thesupport structure122 of thetherapeutic assembly121 includes a proximal portion that defines anorientation region122bof the assembly for locating the therapeutic assembly adjacent to the wall of the renal artery. As shown inFIG. 8A, the proximal region of thesupport structure122 includes a plurality oforientation slots130′. In operation, upon actuation of thehandle assembly134 to place thecontrol wire168 under tension, theorientation region122bdeflects in a radially outward direction within the renal artery to locate thetherapeutic assembly121 into contact with thearterial wall55. More specifically, theslots130′ deform under the tension force so as to deflect theorientation region122bradially outward from the longitudinal axis B-B of thesupport structure122. In the fully deployed state, the resultant helical geometry of thetherapeutic assembly121 at the distal end of thesupport structure122 is preferably offset from the longitudinal axis B-B at the proximal end of thesupport structure122 such that the helical axis H-H and the longitudinal axis B-B of thesupport structure122 are non-coaxial. The axes H-H, B-B may be parallel to one another or, alternatively, skewed with respect to one another.
• The proximal end of thesupport structure122 can be coupled to a separate member forming theelongated shaft116 of thedevice112. Alternatively, thesupport structure122 and theelongated shaft116 may be a single unitary member that extends proximally from thedistal end126ainto thehandle assembly134. In one embodiment, thetubular support structure122 is formed from a metallic shape-memory material (e.g., nitinol). Further, in one embodiment thesupport structure122 can have an axial length of less than five inches (12.7 cm) and, more specifically, about two inches (5.08 cm); an outer diameter of about 0.020 inch (0.57 mm) and, more specifically, ranging between about 0.016 inch (0.41 mm) to about 0.018 inch (0.46 mm); a tubular wall thickness of less than 0.005 inch (0.13 mm) and, more particularly, about 0.003 inch (0.08 mm). In several embodiments, theelongated shaft116 can be formed from stainless steel metal tubing having an outer diameter of, e.g., about 0.020 (0.57 mm) to about 0.060 inch (1.52 mm). In coupling theproximal support structure122 to theelongated shaft116, a joint119 may be provided therebetween to provide the desired transfer of torque from theelongated shaft116 to thesupport structure122 when navigating to the treatment site. More specifically, each end of thesupport structure122 and theelongated shaft116 may respectively include mating notches that permit the ends of the tubular members to interlock with one another as shown in thejoint assembly120. In some embodiments, disposed about the joint119 is a stainless steel sleeve that is crimped about the juncture to provide additional support to the joint119.
• As noted above, thecontrol member168 can be a control rod or wire that extends the axial length of thecatheter device112 from at or near thedistal end126aof thesupport structure122 to thehandle assembly134. Thecontrol wire168 can be comprised of ultra high molecular weight (UHMW) fiber, such as for example high strength, gel-spun fiber sold under the trademark SPECTRA or other sufficiently strong polyethylene fiber. Alternatively, nitinol, a para-aramid synthetic fiber sold under the trademark KEVLAR, or other mono- or multi-filament types can be used provided they are compatible with the application and can transfer the tensile force to the distal end of thetherapeutic assembly121 over the length of thetreatment device112.
• To provide the desired tensile force at the distal end of thetherapeutic assembly121, thecontrol wire168 may be anchored at or near thedistal end126aof thesupport structure122.FIGS. 8B-8D, for example, illustrate various anchoring configurations for thecontrol wire168. More specifically, as shown inFIG. 8B, thedistal end126aof the support structure includes a slot adjacent the axial opening to tie and anchor thecontrol wire168 therethrough. In an alternate anchoring arrangement shown inFIG. 8C, thecontrol wire168 extends through the axial opening at thedistal end126a. Thecontrol wire168 can be encased in acoil174 material to stop thecontrol wire168 from sliding proximally into the distal portion of thesupport structure122.FIG. 8D illustrates anothertip174 configured in accordance with an embodiment of the disclosure. In this arrangement, thecontrol wire168 can be tripled-knotted to provide an enlarged surface of thecontrol wire168 on which to coat the polymer material that is formed into a tip.
• Referring back toFIG. 8A, thecontrol wire168 can extend through theelongated shaft116 to thehandle assembly134. In operation of thehandle assembly134 to tension and release thecontrol wire168 when transforming the therapeutic assembly between deployed and delivered states, friction occurs between the movingcontrol wire168 and the interior of the relatively stationary elongated shaft. One embodiment of thecontrol wire168 assembly is configured to minimize the friction contact between thecontrol wire168 and the interior of theelongated shaft116. For example, as shown inFIG. 8A, asleeve170 can be disposed and bound to thecontrol wire168 to provide a relatively low-friction outer surface. Thesleeve170 preferably has axial length that is less than that of theelongated shaft116 and, more preferably, covers a substantially proximal portion of thecontrol wire168 within theelongated shaft116. During operation of thehandle assembly134 to tension and release thecontrol wire168, thetubular sleeve170 is configured to move with thecontrol wire168 and acts as a bearing surface against the interior of theelongated shaft116, thereby reducing friction between thecontrol wire168 and theelongated shaft116.
• In several embodiments, a control member may be configured to be outside of the support structure of the treatment assembly that carries the energy delivery elements. For example, the support structure of the treatment assembly may instead be externally wound or wrapped around the control member. In such arrangements, the control member engages a portion of the support structure to apply a force that converts the support structure and the treatment assembly between its delivery and deployed state.
• FIGS. 9A and 9B, for example, illustrate a distal portion of atreatment device212 configured in accordance with further embodiments of the present technology. More specifically,FIGS. 9A and 9B illustrate atreatment assembly221 having atubular support structure222 helically wrapped about acontrol member268 with a plurality ofenergy delivery elements224 disposed about thesupport structure222. Thesupport structure222 can include a number of features generally similar to thesupport structures22 and122 described above.
• In the illustrated embodiment, a distal region orportion222aof thesupport structure222 terminates in an end piece (e.g., a conical or bullet-shaped tip250) or, alternatively, a collar, shaft, or cap. Thetip250 can include a rounded distal portion to facilitate atraumatic insertion of thetreatment device212 into a renal artery. A proximal region orportion222bof thesupport structure222 is coupled to and affixed to anelongated shaft216 of thetreatment device212. Theelongated shaft216 defines a central passageway for passage of acontrol member268. Thecontrol member268 may be, for example, a solid wire made from a metal or polymer. Thecontrol member268 extends from theelongated shaft216 and is affixed to thedistal region222aof thesupport structure222 at thetip250. Moreover, thecontrol member268 slidably passes through theelongated shaft216 to anactuator236 in ahandle assembly234.
• In this embodiment, thecontrol member268 is configured to move distally and proximally through theelongated shaft216 so as to move thedistal region222aof thesupport structure222 accordingly. Distal and proximal movement of thedistal region222arespectively lengthen and shorten the axial length of the helix of thesupport structure222 so as to transform thetreatment assembly221 between a delivery (FIG. 9B) and deployed state (FIG. 9A) such that theenergy delivery elements224 move a radial distance Y to engage the walls of the renal artery (not shown).
• In an alternate embodiment, the treatment assembly may not be affixed to a control member at the distal region of the tubular support structure.FIG. 9C, for example, illustrates another embodiment of atreatment device212′ andtreatment assembly221′ having a helical shapedsupport structure222 with a plurality ofenergy delivery elements224 disposed about thehelical support structure222. Adistal end region222aof thesupport structure222 is coupled to acollar element274 that includes a passage sized and shaped to slidably accommodate thecontrol member268 that terminates at anend piece250. In this embodiment, thecontrol member268 comprises control wire that extends from theelongated shaft216 and moves distally and proximally through theelongated shaft216 and thecollar element274. Astopper member275 can be connected to thecontrol wire268 proximal to thecollar element274.
• Thecontrol wire268 facilitates the expansion and/or contraction of thehelical support structure222 when it is pulled or pushed to shorten or lengthen thehelical support structure222. For example, pulling (i.e., an increase in tension) of thecontrol wire268 may trigger expansion of thehelical structure222, while pushing (i.e., an increase in compression) of thecontrol wire268 may lengthen thehelical support structure222 to a compressed configuration. In some embodiments,helical structure222 has elastic or super-elastic properties such that when force is removed thehelical structure222 elastically returns to a relaxed state. Force may be applied by theend piece250 or thestopper member275 to transform thetreatment assembly221′ between the delivery and deployed states. For example, thecontrol wire268 may be pushed distally such that thestopper member275 engages and distally moves thecollar element274 so as to lengthen thesupport structure222 and reduce its diameter placing it in a delivery state. Alternatively, thecontrol wire268 may be pulled proximally to causeend piece250 to engage and proximally move thecollar element274 so as to shorten thehelical support structure222 and increase its diameter, thereby placing it in a deployed state.
• When thehelical support structure222 has a pre-formed helical shape memory, thehelical support structure222 elastically expands to its pre-formed shape when thecollar element274 is not engaged with either thestopper member275 or theend piece250. In this way thehelical support structure222 may expand to contact the inner wall of the renal artery with a relatively consistent force. Furthermore, in some embodiments the force exerted in the renal arterial wall by the pre-formedhelical structure222 may be less dependent on the operator's control at the handle assembly234 (FIG. 9A).
• FIGS. 9D and 9E illustrate another embodiment of atreatment device212″. In this embodiment,control member268′ comprises a hollow tube defining an internal passage for aguide wire266 to facilitate insertion of thetreatment assembly221 through an intravascular path to a renal artery. Accordingly, thetreatment device212″ is configured for an OTW or RX delivery as described herein. Thecontrol member268′ defines an internal lumen extending through the control member and composed of, for example, a polyimide tube with wall thickness less than about 0.003 inch (0.08 mm) (e.g., about 0.001 inch (0.02 mm)) and a lumen with a diameter of less than about 0.015 inch (0.38 mm) (e.g., about 0.014 inch (0.36 mm)). In addition to engaging and tracking along theguide wire266, thedevice212″ transforms the configuration of thetreatment assembly221 between the delivery state and the deployed state in a manner similar to that oftreatment device212 shown and described with respect toFIGS. 9A and 9B.
• FIGS. 10A and 10B are side views of another embodiment of atreatment device310 having an OTW configuration and including atubular control member368 defining a guide wire lumen that extends substantially the entire length of the device. Thecontrol member368 is configured to slidably receive aguide wire366 such that thetreatment device310 may be tracked over theguide wire366 using over-the-wire techniques. Thecontrol member368 is slidably disposed within anelongated shaft316. In one embodiment, thecontrol member368 is allowed to slide relative to theelongated shaft316 within a thin-walled sleeve (not shown) that is attached to an inner surface of theelongated shaft316 using thermal or adhesive bonding methods. The thin-walled sleeve may be formed out of a polymeric material such as, but not limited to, polyimide. In other embodiments, however, thetreatment device310 may not include the sleeve.
• Thetreatment device310 also includes atreatment assembly312 extending between a distal portion of theelongated shaft316 and a distal portion of thecontrol member368. Thetreatment assembly312 is deployable at a target location within the vasculature and includes multiple (e.g., six) energy delivery elements324 (e.g., electrodes) for delivering energy from anenergy generator326 to a vessel wall. In some embodiment, the energy delivery elements orelectrodes324 may be equally spaced apart along the length of thesupport structure322. In other embodiments, however, the number and/or arrangements of theenergy delivery elements324 may vary. The axial length of thesupport structure322 can be between, e.g., about 17 mm to 20 mm. In other embodiments, however, thesupport structure322 may have a different length so long as the structure sufficiently supports the number of electrodes in a desired electrode spacing pattern.
• Theenergy delivery elements324 may be a series of separate band electrodes spaced along thatsupport structure322. Band or tubular electrodes may be used in some embodiments, for example, because they have lower power requirements for ablation as compared to disc or flat electrodes. In other embodiments, however, disc or flat electrodes are also suitable for use. In still another embodiment, electrodes having a spiral or coil shape may be utilized. In one embodiment, the individualenergy delivery elements324 may have a length ranging from approximately 1-5 mm, and the spacing between each of theenergy delivery elements324 may range from approximately 1-10 mm. In other embodiments, however, theenergy delivery elements324 may have different dimensions and/or arrangements.
• Theenergy delivery elements324 may be formed from any suitable metallic material (e.g., gold, platinum, an alloy of platinum and iridium, etc.). In one embodiment, for example,energy delivery elements324 may be 99.95% pure gold with an inner diameter that ranges between about 0.025 inch (0.64 mm) and 0.030 inch (0.76 mm), and an outer diameter that ranges between about 0.030 inch (0.76 mm) and 0.035 inch (0.89 mm). Electrodes of smaller or larger dimensions, i.e., diameter and length, are also suitable for use herein.
• Each energy delivery element orelectrode324 is electrically connected to thegenerator326 by a conductor or wire (not shown) extending through a lumen of theelongated shaft316. Eachelectrode324 may be welded or otherwise electrically coupled to the distal end of its energy supply wire and each wire can extend through theelongated shaft316 for the entire length of shaft such that a proximal end thereof is coupled to thegenerator326.
• Thesupport structure322 may comprise a shape memory component that extends at least the length of theassembly312. Shapememory support structure322 is utilized to deploy or transform thetreatment assembly312 from a delivery state shown inFIG. 10A (i.e., a substantially straightened form) to a deployed state shown inFIG. 10B (i.e., a preset spiral or helical form). More particularly, the shape memory component ofsupport structure322 may be constructed from a shape memory material that is pre-formed or pre-shaped into the deployed state. Certain shape memory materials have the ability to return to a predefined or predetermined shape when subjected to certain thermal conditions. When shape memory materials, such as nickel-titanium (nitinol) or shape memory polymers or electro-active polymers, are at a relatively low temperature, items formed therefrom may generally be deformed quite easily into a new shape that they retain until exposed to a relatively higher transformation temperature, which in embodiments hereof is above a normal body temperature of 37° C., that then returns the items to the predefined or predetermined shape they held prior to the deformation. In some embodiments,support structure322 may be formed from such a shape memory material, inserted into the body in a deformed, low profile straightened state, and returned to a “remembered” preset shape once shapememory support structure322 is exposed to a transformation temperature in vivo. Thus, shapememory support structure322 has at least two stages of size or shape, a generally straightened or stretched-out coil configuration of a sufficiently low profile for delivery to the treatment site as shown inFIG. 10A and a spiral or helical configuration that placesenergy delivery elements324 into contact with avessel wall55, which is shown as a dashed line inFIG. 10B. The delivery state may also be achieved by mechanically straightening shapememory support structure322 by the operator or via a tensioning device. Referring toFIG. 10A, in one embodiment a delivery diameter D1 of shapememory support structure322 may be between about 1 and 2 mm to accommodate delivery to a target vessel, such as a renal artery.
• Thetreatment assembly312 may also include an insulating component (not shown) that functions to electrically isolate shapememory support structure322 from theenergy delivery element324. The insulating component, for example, can include a tubular sheath defining a lumen that is formed from an electrically insulative material, such as polyethylene block amide copolymer. In an embodiment, the insulating component may have an outer diameter of approximately 0.027 inch (0.69 mm) and an inner diameter of approximately 0.023 inch (0.59 mm). The insulating component is configured to house shapememory support structure322 as well as housing wires to provide additional protection thereto, andelectrodes324 are attached to or disposed around insulating component. A distal end of the insulating component may be attached to a distal end ofguide wire shaft368 by any suitable method such as an adhesive, a sleeve, or other mechanical method. In one embodiment depicted inFIG. 10A, the distal end of the insulating component is preferably attached to the distal end ofguide wire shaft368 via a cyanoacrylate adhesive and a polymer sleeve surrounds and holds together the distal ends to form a tapereddistal tip350 of thetreatment assembly312. In other embodiments, however, the insulating component may have a different arrangement relative to thetreatment assembly312.
• Both shapememory support structure322 and the insulating component preferably extend along thelength treatment assembly312 and proximally extend into the distal end of theshaft316, e.g., at least one or two centimeters, such that the proximal end of shapememory support structure322 is sufficiently removed from theenergy delivery elements324 to avoid any thermal effects therefrom.
• As the shapememory support structure322 of thetreatment assembly312 assumes the deployed configuration, the distal end of the insulating component proximally retracts such that thetreatment assembly312 radially expands into contact with vessel wall, since the distal end of the insulating component is coupled to distal end of innertubular shaft368. Thecontrol member368 also slightly proximally retracts withinelongated shaft316 in order to allow deployment of thetreatment assembly312.
• In each of the previously described embodiments of the treatment or therapeutic devices, the control member is configured as a wire, tubular shaft or other inner member that applies a force at or near the distal end of the support structure to alter the configuration of the therapeutic assembly between a delivery state and a deployed state. In other embodiments, however, an actuating force may be applied at or near the proximal end of the therapeutic assembly to transform the configuration of the assembly.
• FIGS. 11A and 11B, for example, illustrate an embodiment of atreatment device612 configured to apply a deforming force to a proximal end of the treatment assembly. Thetreatment device612 includes a tubularelongated shaft616 having a proximal end coupled to ahandle assembly634 and a distal end coupled to atreatment assembly621. The illustratedtreatment assembly621 includes atubular support structure622 carrying a plurality ofenergy delivery elements624. Energy supply wires (omitted for clarity) extend internally or externally along thesupport structure622 to provide a treatment energy to theenergy delivery elements624. Aproximal end622bof thesupport structure622 is disposed within and affixed to the distal end of the tubularelongated shaft616. Thesupport structure622 defines a preferably helical shape wrapped about atubular control member668 having an internal lumen for passage of aguide wire666 that can extend distally beyond thetreatment assembly621 and proximally beyond thehandle assembly634. Accordingly, thetreatment device612 is configured for an over-the-wire delivery. The support structuredistal end622ais coupled to a distal region of thetubular control member668. Thecontrol member668 extends proximally into theelongated shaft616 and is affixed to an internal surface of thehandle assembly634. Accordingly, thedistal end622aof thesupport structure622 can remain at a fixed distance from thehandle assembly634.
• Theelongated shaft616 extends proximally into thehandle assembly634, and is coupled to anactuator636. In one embodiment, theactuator636 provides for linear displacement or direct longitudinal translation of theelongated shaft616. Theactuator636 is shown schematically as a slider-in-groove assembly. In operation, proximal translation of theactuator636 translates theaxial shaft616 proximally with respect to handleassembly634 and thus toinner member668. The distal end of theelongated shaft616 applies a tension force to the affixedproximal end622bof thesupport structure622. Because thedistal end622aof thesupport structure622 is affixed to thecontrol member668, proximal translation of theproximal end622aof thesupport structure622 elongates the structure so as to place thetreatment assembly612 in a low profile delivery state (FIG. 11A). Distal translation of theactuator636 results in compressing thesupport structure622 axially so as to place thetreatment assembly612 into a deployed state (as best seen inFIG. 11B).
• Alternate configurations of thehandle assembly634 can provide the desired axial translation of theelongated shaft616.FIG. 11C, for example, illustrates an alternate arrangement of thehandle assembly634 that provides for a pivot-type actuator636′ to axially translate theelongated shaft616. Theactuator636′ can include a pivot connection to theelongated shaft616. Accordingly, angular rotation ofactuator636′ about the pivot connection linearly translates theelongated shaft616. The amount of angular rotation of theactuator636′ can be controlled by the distance betweenelongated shaft616 and the pivot point.FIG. 11D illustrates another alternate configuration of thehandle assembly634 including a gear-type actuator636″ to linearly translate theelongated shaft616. In one embodiment, for example, theactuator636″ includes a knob or thumb roller connected to a small gear. Theelongated shaft616 may be connected to a larger gear engaged with the a small gear such that the small gear rotates, which in turn rotates the larger gear and translates theelongated shaft616. The difference in gear sizes allows a small roller rotation to create a large translation of theelongated shaft616.
• In the previously described embodiments of the treatment device, the treatment assembly of the devices was altered between a delivery state and a deployed state by pushing or pulling on either a proximal end or a distal end of the support structure depending upon the configuration. It should be understood that the treatment device may be configured for selectively applying a force at or near either the proximal or the distal end of the support structure such that a clinician may select the end for relevant movement depending, for example, the constraints around the supporting structure.
• In several alternate configurations, the treatment assembly can be movable between the delivery and deployed states by either inserting or retracting a control member (e.g., an insertion member, stylet, pre-shaped member, etc.) into a distal treatment section or portion of a tubular support structure.FIGS. 12A and 12B, for example, are side perspective views of a portion of atreatment device700 configured in accordance with an additional embodiment of the technology. More specifically,FIG. 12A illustrates thetreatment device700 in a delivery state (e.g., low-profile or collapsed configuration) outside a patient, andFIG. 12B illustrates thetreatment device700 in a deployed state (e.g., expanded configuration). Referring toFIGS. 12A and 12B together, thetreatment device700 includes anelongated shaft701 having adistal portion702, and atreatment section704 at thedistal portion702. Thetreatment device700 also includes a plurality ofenergy delivery elements706 carried by thetreatment section704. Thetreatment device700 further includes a control member708 (shown schematically in broken lines) coupled to thetreatment device700 and slidably moveable relative to thetreatment section704. As will be described in greater detail below, thetreatment section704 or thecontrol member708 comprises a pre-formed helical shape, and the other of thetreatment section704 and thecontrol member708 comprises a substantially straight shape. Thetreatment section704 and thecontrol member708 are movable relative to one another to alter thetreatment device700 between a low-profile delivery state (FIG. 12A) and an expanded delivery state having the pre-formed helical shape (FIG. 12B). For purposes of illustration,control member708 is shown in bothFIGS. 12A and 12B. As described in greater detail below, in various embodiments, thecontrol member708 may be either inserted into or withdrawn from thetreatment section704 to alter thetreatment device700 between the delivery and deployed states.
• For example, in one embodiment described below, thecontrol member708 can include a stylet, stiffening mandrel, straightening member, or a procedural guide wire extending along at least a portion of the length of thetreatment device700 and configured to straighten a pre-shapedhelical treatment section704 of thetreatment device700 during delivery. More specifically, thecontrol member708 facilitates the expansion and/or contraction of thetreatment section704 when thecontrol member708 is pulled or pushed, respectively, relative to thetreatment section704. In another embodiment, a pre-shaped control member (e.g., stylet or pre-shaped member) can provide a helical shape to a relatively flexible,distal portion702 of thetreatment device700.
• FIGS. 13A-15B are directed to various embodiments of treatment devices including features generally similar to thetreatment device700 described above with reference toFIGS. 12A and 12B.FIGS. 13A and 13B, for example, are cross-sectional views of atreatment device712 including a treatment section orassembly721 having a plurality ofenergy delivery elements724 carried by a relatively flexibletubular support structure722 defining acentral lumen729. Thetubular support structure722 includes adistal end722ahaving an axial opening for passage of a guide wire766 (FIG. 13A) extending through thelumen729. Thetubular support structure722 has aproximal end722bcoupled to or affixed to the distal end of a tubularelongated shaft716. Theelongated shaft716 defines a central lumen for housing theguide wire766. Accordingly, the present configuration provides for an over-the-wire delivery from an access site in which theguide wire766 is initially inserted to a treatment site (e.g., within a renal artery), and thetreatment device712 is installed over theguide wire766. Inserting the substantially straight andlinear guide wire766 through the flexibletubular support structure722 maintains thetubular support structure722 in a normally straight shape so as to place thetreatment assembly721 into a low profile delivery state for delivery to the treatment site in the renal artery. Theguide wire766 may be of a constant stiffness along its length or may have a variable stiffness or flexibility along its length so as to provide increased flexibility, for example, in the proximal to distal direction.
• Once thetreatment device712 is delivered overguide wire766 to a desired position within the renal artery, theguide wire766 is refracted completely fromtreatment device712 and an elongate control member768 (FIG. 13B) is inserted at a proximal end of thedevice712 and advanced distally through theelongated shaft716 into thecentral lumen729 of thetubular support structure722. The distal region of thecontrol member768 can have a pre-set deployed shape (e.g., a helical shape) when unconstrained to define the deployed state of thetreatment assembly721. Thecontrol member768 may be made from a super-elastic nitinol material having a pre-set or pre-formed helical shape. Alternatively, the control member can be made from a shape-memory material.
• Thecontrol member768 is sufficiently elastic so as to be straightened for insertion at the proximal end of the device, for example, at thehandle734. Thecontrol member768 may be inserted directly into theelongated shaft716. Alternatively, thecontrol member768 may be first housed inside of a more rigid insertion tube769 (FIG. 13B) to straighten out thecontrol wire768 and facilitate insertion of thecontrol member768 into thecatheter device712. In this embodiment, thetreatment assembly721 can be inserted into the proximal end of theelongated shaft716 and, once located at the treatment site within the renal artery, theinsertion tube769 can be retracted to allow thecontrol member768 to deploy. As shown inFIG. 13B, thecontrol member768 imparts a force on thetubular support structure722, thereby deforming it in to an expanded helical configuration and deploying thetreatment assembly721 to locate theenergy delivery elements724 against the wall of the renal artery.
• In a particular embodiment, a plurality ofelectrical delivery elements724 are configured asmultiple electrodes724 mounted onto a flexible, somewhat distensible tube722 (e.g., a tube made of polyethylene block amide copolymer such as PEBAX® 5533D, or a lower durometer material). In other embodiments, thetubular support structure722 may be constructed from other polymers, e.g., PET, polyamide, polyimide, PEBAX, polypropylene, or PEEK polymers that provide the desired flexibility. In one embodiment, thetubular support structure722 has an inner diameter of about 0.03 inch (0.76 mm) and an outer diameter of about 0.04 inch (1.02 mm) and a length of about 4 cm. Theelectrodes724 can be cylindrical electrodes and, in one embodiment, can have an inner diameter of about 0.042 inch (1.07 mm), an outer diameter of about 0.046 inch (1.17 mm), and a length of about 1 mm. Theelectrodes724 can be spaced between 3 to 5 mm apart and bonded to thetubular support structure722 using an adhesive. Electrode conductivepower supply wires725 can extend proximally along and outside thetubular support structure722.
• In several embodiments, theproximal end722bof theflexible support structure722 with theelectrodes724 is placed over the distal end of tubularelongated shaft716 and bonded in place. Theelongated shaft716, for example, can include a polyamide tube. In one embodiment, theshaft716 has an inner diameter about of 0.025 inch (0.64 mm) and an outer diameter of about 0.03 inch (0.76 mm) with a length of about 100 cm. In other embodiments, the elongated shaft has an inner diameter of 0.026 inch (0.66 mm) and an outer diameter of 0.028 inch (0.71 mm) and/or other suitable dimensions. An outertubular jacket717 can surround theshaft716 and abut or overlap theproximal end722aof thetubular support structure722.
• Thecontrol member768 for deploying thetreatment assembly721 can include, for example, a nitinol wire pre-shaped with a helical configuration over the distal region of thecontrol member768. In one embodiment, thecontrol member768 has a diameter of about 0.015 inch (0.38 mm) and tapers distally to a tip having a diameter of 0.008 inch (0.20 mm). Several different diameters ofpre-shaped control members768 can be made to accommodate different diameter renal arteries with each having a diameter ranging from about 4.0 mm to about 8.0 mm. Thecontrol member768 can have a shape memory transformation temperature that is slightly above body temperature (e.g., austenite finish temperature A_f=42° C.). Thecontrol member768 is more pliable at temperatures below the A_f<, and therefore the helical region can be straightened manually with relative ease. Accordingly, thecontrol member768 can then be inserted directly into the proximal end of the catheter without the need for the “rigid insertion tube769.” Once the distal region of thecontrol member768 is positioned within thetubular support structure722 surrounded by themultiple electrodes824, raising the temperature of the shapememory control member768 above the A_fwill allow it to assume the helical configuration, deform thetubular support structure722 and press theelectrodes724 into the arterial wall allowing the tissue ablation to occur. Once the ablation is completed and theenergy source26 turned off, the surrounding blood flow can cool theelectrodes724 and thecontrol member768 below the A_f, allowing thecontrol member768 to become more pliable for removal from the catheter. Those skilled in the art will understand that various methods can be used to heat thecontrol member768 to transform its shape.
• In the embodiment illustrated inFIG. 13B, thecontrol member768 is disposed in theoptional insertion tube769. Theinsertion tube769 can be made from a variety of materials including braided polyimide, PEEK, and/or stainless steel and can have dimensions such that theinsertion tube769 can slide easily through theelongated shaft716. Thepre-shaped control member768 has a total axial delivery length that is greater that then the axial length of theinsertion tube769 such that theguide wire766 can be advanced and retracted from the proximal end of thecatheter device712.
• In the above described embodiments that use the flexibletubular support structure722 and theinsertion tube769 for delivery and deployment of the therapeutic assembly, the guide wire is completely removed from thetubular support structure722 before insertion of thepre-shaped control member768 because there is only a single lumen in the elongated shaft of the catheter for receiving theguide wire766 and thecontrol member768. Further embodiments of treatment devices, however, include for an elongated shaft with multiple lumens to provide multiple passageways in which to hold a control member, a guide wire, supply wires, and/or an injectable fluid (e.g., contrast, medicine, or saline). Accordingly, such treatment devices provide for an over-the-wire delivery and deployment of a treatment assembly with an insertable member without the need to remove the guide wire completely from the catheter.
• FIGS. 14A and 14B, for example, are broken longitudinal cross-sectional views of atreatment device812 configured in accordance with another embodiment of the present technology. As shown inFIG. 14A, thetreatment device812 includes atreatment assembly821 having a plurality ofenergy delivery elements824 carried by a relatively flexibletubular support structure822 defining acentral lumen829. Thetubular support structure822 includes adistal end822ahaving anaxial opening823 for passage of aguide wire866 extending through thecentral lumen829. Thetubular support structure822 has aproximal end822bcoupled or affixed to the distal end of an elongatedtubular shaft816. Theelongated shaft816 can define a firstinternal lumen813 for housing theguide wire866. Theguide wire866 exits proximally from a conventional hub/luer fitting located, for example, at thehandle834. Accordingly, the illustrated configuration provides for an OTW delivery from the access site to the treatment site. Inserting the substantiallystraight guide wire866 through the flexibletubular support structure822 straightens thetubular support structure822 so as to place thetreatment assembly821 into a low profile delivery state for delivery to the treatment site in the renal artery.
• Thetubular shaft816 further includes a second internal lumen814 for housing acontrol member868 for deployment of thetreatment assembly821. Thetubular shaft816 may have multiple lumens to hold the shape insertion members, supply wires, and/or an injectable fluid (e.g., contrast, medicine, or saline).FIGS. 14A and 14B show the twolumens813,814 formed within the integraltubular shaft816. Alternatively, the first andsecond lumens813 and814 can be defined by separate tubular shafts disposed within the outertubular shaft816. Within the second internal lumen814 of thetubular shaft816, thecontrol member868 can be maintained in a substantially linear configuration. Once thetreatment device812 is placed in a desired position within a renal artery, theguide wire866 can be refracted from thetubular support structure822 into thefirst lumen813, and thecontrol member868 can be advanced distally into thecentral lumen829 of thetubular support structure822. Because each of thecontrol member868 and theguide wire866 have independent lumens in which they reside, theguide wire866 needs only be retracted a sufficient distance proximally to exit thetubular support structure822 of thetreatment assembly821 so as to allow thecontrol member868 to fill thesupport structure822 and deploy thetreatment assembly821. In several embodiments, for example, theguide wire866 can be retracted 10-20 cm (e.g., about 15 cm) to clear thetubular support structure822 for deployment of thetreatment assembly821.
• Thecontrol member868 can have a pre-set deployed shape that defines a helical shape when unconstrained to define the deployed state of thetreatment assembly821. Thecontrol member868 may be made from a super-elastic nitinol material having a pre-set helical shape. Once located within thesupport structure822, theelastic control member868 can impart a force on thetubular support structure822 deforming it in to an expanded helical configuration (e.g., as shown inFIG. 14B), so as to deploy thetreatment assembly821 and locate theenergy delivery elements824 against the wall of the renal artery.
• In other embodiments of the device with the multi-lumen elongated shaft, a tubular support structure can include at least two or more independent lumens or passageways. For example,FIGS. 14C and 14D illustrate a treatment device912 including atreatment assembly921 with a plurality ofenergy delivery elements924. Atubular support structure922 defines at least two internal lumens. Afirst lumen928 can include an axial opening at its distal end and can be adapted to accept aguide wire966 having a diameter of less than about 0.015 inch (0.38 mm) for insertion and retraction from thefirst lumen928. Accordingly, thesupport structure922 can be delivered into a renal artery using an OTW approach as discussed above. In other embodiments, thedistal end922aof thetubular support structure922 may terminate in a rounded distal tip to facilitate atraumatic insertion of the treatment device into the renal artery. Asecond lumen930 is adapted to hold adeployment member968 having a pre-set distal region defining a helical shape in a deployed state.
• Thetherapeutic assembly921 can be placed into a low-profile delivery state (e.g., as shown inFIG. 14C) by inserting theguide wire966 through thefirst lumen928 of thesupport structure922 for delivery to a renal artery. The substantiallylinear guide wire966 can overcome the pre-set helical shape in theflexible deployment member968 to maintain thetherapeutic assembly921 in the delivery state. Theguide wire966 may be of a constant stiffness along its length or, alternatively, may have a variable stiffness or flexibility along its length so as to provide increased stiffness, for example, in the proximal to distal direction. Once thetreatment assembly921 is positioned at the target treatment site in the renal artery, thetherapeutic assembly921 can be deployed by retracting theguide wire966 out of thefirst lumen928 of thesupport structure922 such that it is generally located within the elongated shaft916 (e.g., within one of the plurality of lumens formed within the elongated shaft916). With theguide wire966 removed from thesupport structure922, thedeployment member968 can impart a deforming force on thetubular support structure922 that deforms it to the helical shape so as to deploy the therapeutic assembly921 (e.g., as shown inFIG. 14D). Accordingly, theguide wire966 provides a control member to alter the therapeutic assembly between the delivery and the deployed states. Optionally, thefirst lumen928 may be used to deliver a fluid distally, such as saline to cool theenergy delivery element924 during energy delivery.
• In another embodiment, thedeployment member968 may be retractable to control the delivery and deployment states of thetreatment assembly921 and theguide wire966 or other straightening stylet can remain in thefirst lumen928 during deployment. In such an arrangement, theguide wire966 can be sufficiently rigid to place thetreatment assembly921 in the low profile configuration for delivery, yet flexible enough to allow thedeployment member968 to impart a force on theassembly921 to place thesupport structure922 and thetreatment assembly921 in the deployment configuration.
• FIGS. 15A and 15B illustrate still another embodiment atreatment device1012 that allows aguide wire1066 to remain at least partially inserted in anelongated shaft1016 during treatment. As shown inFIG. 15A, thetreatment device1012 includes a single lumen in each of atubular support structure1022 and theelongated shaft1016. Thetreatment device1012 includes atreatment assembly1021 having a plurality ofenergy delivery elements1024 mounted to thetubular support structure1022 defining a singlecentral lumen1029. Thesupport structure1022 may be covered with an electrical insulator, e.g., with a heat shrink tube of a polymer such as PET. Thetubular support structure1022 may also include adistal end1022ahaving anaxial opening1023 to allow theguide wire1066 to project beyond thedistal end1022a. In some embodiments, thedistal end1022amay terminate in a rounded distal portion (e.g., as shown in broken lines). Thetubular support structure1022 can have aproximal end1022bcoupled to the distal end of theelongated shaft1016. Thecentral lumen1029 of thesupport structure1022 can extend through theelongated shaft1016 to receive theguide wire1066 and allow for an OTW delivery. In operation, inserting the substantiallystraight guide wire1066 through thetubular support structure1022 straightens thetubular support structure1022 so as to place thetreatment assembly1021 into a low-profile delivery state (e.g., as shown inFIG. 15A) for delivery to the treatment site in the renal artery.
• Thetubular support member1022 may be made from an elastic or super elastic material, e.g., nitinol tubing or polymer-composite tubing including braided or coiled filaments of nitinol. In several embodiments, thesupport structure1022 can have an inner diameter less than or equal to about 0.015 inch (0.38 mm), e.g., about 0.010 inch (0.25 mm), and a wall thickness of less than about 0.005 inch (0.13 mm), e.g., about 0.003 inch (0.76 mm). Thetubular support structure1022 may also be made from a shape-memory material, e.g., nitinol having a pre-formed helical deployed shape. As an alternative to using a pre-formed shape, thetubular support structure1022 may includes a pre-shaped inner member (e.g., inner tubing) or an outer frame structure (not shown) that biases thetubular support structure1022 into the helical deployment configuration.
• With theguide wire1066 disposed in thecentral lumen1029, theguide wire1066 imparts a straightening force on thetubular support structure1022 so as to define the low profile or collapsed delivery configuration shown inFIG. 15A. Theguide wire1066 may be of a constant stiffness along its length or, alternatively, may have a variable stiffness or flexibility along its length so as to provide increased flexibility (e.g., in the proximal to distal direction). To deploy thetreatment assembly1021, theguide wire1066 can be retracted proximally into theelongated shaft1016 so as to remove theguide wire1066 from thesupport structure1022. As shown inFIG. 15B, in the absence of a straightening force, thesupport structure1022 can deploy into a helical configuration. Accordingly, theguide wire1066 acts as a control member for altering the configuration of thetreatment assembly1021 between the delivery and the deployed states.
• Although the embodiments of the treatment or catheter devices previously described include an arrangement of the treatment assembly and a control member to place the assembly in a low-profile delivery state, the catheter devices may further include an external sheath that can be disposed and retracted over the treatment assembly to alter its delivery and deployed configurations. For example, as shown inFIGS. 16A and 16B, atreatment device1212 can be used in conjunction with adelivery sheath1291 that forms a sheath around atreatment assembly1221 and anelongated shaft1216. As noted, in certain embodiments, it may be advantageous to use aguide catheter1290 of a particular size to facilitate insertion of thetreatment device1221 through the femoral artery. Adelivery sheath1291 may be used in conjunction with theguide catheter1290 to gain access to a renal artery and deliver a contained expandablehelical structure1222. Alternatively, thedelivery sheath1291 may be used in conjunction with a guide wire (not shown) as described previously. When used in conjunction with theguide catheter1290, a working length of theelongated shaft1216 may be about 40 cm to about 125 cm. If, for example, a 55 cm length guide catheter is used, then this working length may be about 70 cm to about 80 cm. If a 90 cmlength guide catheter1290 is used, then this working length may be about 105 cm to about 115 cm. In a representative embodiment where noguide catheter1290 is used, then this working length may be about 40 cm to about 50 cm. In still other embodiments, a variety of other different dimensions and/or arrangements may be used.
• In the depicted embodiment, thetreatment assembly1221 includes ahelical structure1222 that may be held in a low profile delivery configuration by thedelivery sheath1291. Removal of thedelivery sheath1291 allows thehelical support structure1222 to deploy and place theenergy delivery elements1224 into contact with the wall of the renal artery. The deployment of thesupport structure1222 may be passive (e.g., the structure has a pre-set deployed shape) or active (e.g., the deployment is facilitated by a pre-shaped stylet or a tension wire). Regardless of the type of expansion, thehelical support structure1222 may by coupled to a control member (e.g., a control wire) that compresses the helical structure prior to removal or repositioning of thetreatment device1212. In particular embodiments, depending on the placement and number ofenergy delivery elements1224, thehelical support structure1222 may be progressively repositioned within the renal artery to provide a plurality of locations for energy delivery.FIG. 16B shows the embodiment of a catheter with ahelical structure1222 ofFIG. 16A with thedelivery sheath1291 retracted allowing thehelical structure22 to elastically expand to its deployed configuration in a renal artery. It should be noted that, inFIG. 16A, thesheath1291 andtreatment assembly1221 are drawn oversized for clarity.
• In one particular embodiment, a sheath can be used to hold the components of the treatment assembly together, particularly as the device is navigated through to the treatment site within the renal artery. With reference toFIGS. 9A and 9B, thetreatment assembly221 can include a spine orsupport structure222 of nitinol material with a plurality ofelectrodes224 disposed thereabout. Thenitinol support structure222 can be helically wrapped about a braided polyamideinner member268. In the delivery state of thetreatment assembly221 ofFIG. 9B, thesupport structure222 may lie adjacent to theinner member268 over its length. In order to minimize substantial separation between thesupport structure222 and theinner member268 when thetreatment assembly221 is bent or curved during delivery, a sheath can be disposed over thetreatment assembly221. Sheaths may also be employed with the treatment assemblies described above with reference toFIGS. 10A-11B and other suitable treatment assemblies described herein.
• A sheath may also be used to support a treatment assembly in its delivery configuration, even when the treatment assembly has a shape-forming insertion member disposed in the lumen of the flexible tubular support structure. For example, with reference toFIGS. 13A and 13B, a sheath (not shown) can be disposed oversupport structure722. Upon retraction of theguide wire766 and insertion of acontrol member768 into the lumen of thesupport structure722, the sheath prevents thetreatment assembly721 from deploying to its fullest transverse dimension. To permit theassembly721 to deploy completely to the desired helical configuration, the sheath can be retracted. Alternatively or in addition, thetubular support structure722 is preferable stiff enough to allow for guidable insertion to the treatment site without the use of the stylet or shaping member, but flexible enough to take on the shape of the insertedcontrol member768 once the sheath is withdrawn. Further, in the alternative or in addition to, theinsertable control member768 can be sheathed to minimize or eliminate the premature deployment of the treatment assembly upon insertion of the control member. Accordingly, once the sheath is removed, theinsertion member768 can expand to its full deployment configuration.
• In still further embodiments with reference toFIGS. 13A and 13B, thestylet768 is positioned in the distalend treatment assembly721 of thedevice712 while the device is at the treatment site (e.g., within the renal artery). In this embodiment, for example, thestylet768 is sheathed in a low-profile configuration during insertion byinsertion tube769. Theinsertion tube769 is removed from thepre-formed stylet768 after insertion, allowing thestylet768 to take its helical shape in the manner described above. In this embodiment, thestylet768 can provide structure and a desired level of rigidity to thedevice712 to help guide and position thedevice712 during delivery and then give it the desired helical arrangement upon deployment.
• In some of the over-the-wire embodiments of the treatment catheter device described above, the guide wire is described as extending within the elongated shaft of the catheter from at least the distal end of the treatment assembly to a location proximal of the handle assembly. In order to disengage the catheter from the guide wire requires retracting the full length of the guide wire proximally from the access site. Accordingly, the guide wire axial length may be greater than that of the catheter elongated shaft and its distal treatment assembly. To provide for an operation and manipulation of a shorter guide wire, and in particular to minimize the retraction distance to disengage the catheter from the guide wire, it may be desirable to have a treatment catheter device that provides for a rapid-exchange configuration. The rapid exchange examples described below with reference toFIGS. 17A-17E may also be used with any of the treatment devices described herein that employ a guide wire and OTW delivery techniques.
• FIG. 17A, for example, is a broken side view in part section of a distal portion of atreatment device1410 with a rapid exchange configuration in accordance with an embodiment of the technology. Thetreatment device1410 includes atreatment assembly1421 helically disposed about atubular control member1468 that defines an internal lumen for passage over aguide wire1466. Thetubular control member1468 extends proximally within theelongated shaft1416 of thetreatment device1410, which is shown at least partially disposed within aguide catheter1490. To provide for a rapid exchange configuration in which theguide wire1466 extends at least partially parallel to and externally to theelongated shaft1416, thetubular control member1468 includes anopening1470 proximal to thetreatment assembly1421, but distal of a handle assembly (not shown) for exit of theguide wire1466. Theelongated shaft1416 also preferably includes anopening1472 for exit of theguide wire1466 and passage into theguide catheter1490. Because theguide wire1466 does not need to extend proximally through theelongated shaft1416 to the handle assembly (not shown), its overall length can be reduced.
• FIGS. 17B and 17C illustrate another embodiment of atreatment device1600 with a rapid exchange configuration in accordance with another embodiment of the technology. More specifically,FIG. 17B is a broken side view in part section of a distal portion thetreatment device1600 in a delivery state, andFIG. 17C is a broken side view of thetreatment device1600 in a deployed state. Referring toFIGS. 17B and 17C together, thetreatment device1600 includes atreatment assembly1621 having atubular support structure1622 with a plurality ofenergy delivery elements1624 disposed about thesupport structure1622. Thesupport structure1622 extends proximally within at least a portion of theelongated shaft1616 of thetreatment device1600.Energy supply wires1625 preferably extend within thetubular support structure1622 to provide energy from an external generator source (not shown) to each of theenergy delivery elements1624. Thetubular support structure1622 extends distally about atubular member1680 in a spiral or helical manner and terminates along an outer surface of thetubular member1680 and is preferably bonded at adistal region1680aof thetubular member1680.
• Thetubular member1680 provides thetreatment assembly1621 with an inner member disposed within the helix defined by thesupport structure1622 that can be used to control the distal region of thesupport structure1622 to alter thesupport structure1622 of thetreatment assembly1621 between a delivery and a deployed configuration. Thetreatment device1600 further includes acontrol member1668 coupled to a proximal region of thetubular member1680 for pushing distally and pulling proximally theinner member1680 so as to move respectively thedistal end1622aof thetubular support structure1622 in the distal and proximal directions with respect to the distal end of theshaft1616. Distal movement of thedistal end1622aof thesupport structure1622 lengthens an axial length of the helical shapedsupport structure1622 and places thetreatment assembly1621 in the delivery configuration (as seen inFIG. 17B). Likewise, proximal movement of thedistal end1622aof thesupport structure1622 shortens an axial length of the helical shapedsupport structure1622 to place thetreatment assembly1621 in the deployed configuration shown inFIG. 17C. In one embodiment, thecontrol member1668 may be configured as a push-pull rod. For example, the push-pull rod can extend axially within theelongated shaft1616 and, in some embodiments, within an independent lumen in theelongated shaft1616 separate from a lumen carryingpower supply wires1625 for thetreatment assembly1621.
• The tubularinner member1680 defines a internal lumen for passage of aguide wire1666. Accordingly, the tubularinner member1680 includes an axial opening at adistal end region1680afor passage of theguide wire1666. Theproximal end region1680bof the tubularinner member1680 is configured for a proximal passage and exit of theguide wire1666. Theproximal region1680bmay terminate, for example, in an obliqueelongated opening1682 for exiting of theguide wire1666. In some embodiments, theproximal region1680bof theinner member1680 may be affixed to the distal end of the push-pull member1668 such that the push-pull member1668 can control the axial distance between theguide wire exit1682 and theelongated shaft1668. Further, in some embodiments the distal end of the push-pull member1668 may include a taper or angled end to increase the cross-sectional area of the push-pull member1668 for bonding to theinner tubular member1680. Because the arrangement of theinner member1680 and the push-pull member1668 maintains the guide wire exit opening external to theelongated shaft1616, the arrangement provides for a rapid exchange configuration.
• In particular, the guidewire exit opening1682 provides that theguide wire1666 can extend parallel and external to theelongated shaft1616. Thus, manipulation of theguide wire1666 does not require that theguide wire1666 extend proximally within the full length of theelongated shaft1616 and beyond, for example, through a handle assembly. Accordingly, in some embodiments theguide wire length1666 may have a reduced length, e.g., about 180 cm. Moreover, to the extent it may be desired to disengage thetreatment assembly1621 from theguide wire1666, theguide wire1666 need only be retracted an amount sufficient to proximally retract the distal end of the guide wire from the guidewire exit opening1682.
• In one embodiment, theelongated shaft1616 is configured to engage the proximal region of theinner tubular member1680 in the deployed configuration of thetreatment assembly1621. More specifically, the distal region of theelongated shaft1616 is formed so as to form a mating fit with the external portion of theproximal end1680bof thetubular member1680 in the deployed configuration. As shown inFIG. 17C, the push-pull member1668 is fully retracted so as to deploy thetreatment assembly1621. The retraction of the push-pull member1668 locates theproximal end1680badjacent the distal end ofelongated shaft1616. The distal end of theelongated shaft1616 preferably includes a taper such that the internal lumen for theenergy supply wires1625 and the linear portion of thetubular support structure1622 extend distally beyond the internal lumen which houses the push-pull member1668. The taper (e.g., skived or oblique notch) at the distal end of theelongated shaft1616 is sized and shaped to receive theproximal end1680bof the inner tubular member when located adjacent theelongated shaft1616.
• In one embodiment, thetreatment assembly1621 may have a maximum delivery length ranging from, for example, about 8 mm to about 50 mm, e.g., about 15 mm to about 50 mm. In a deployed configuration, thetreatment assembly1621 may have a maximum axial length of, e.g., about 45 mm. Thetubular member1680 may have an axial length ranging from about 2-50 cm. with anopening1682 having an axial length of, e.g., about 2-8 mm. The push-pull rod1668 may be configured to alter the axial distance between the distal end of theelongated shaft1616 and theopening1682 of theinner tubular member1680 over a distance of, e.g., 1 mm to about 30 mm. Theelongated shaft1616 and theguide wire1666 may extend parallel to one another within a surroundingguide catheter1690. The catheter device1612 can be configured such that theopening1682 is located inside or outside theguide catheter1690.
• An alternate embodiment of the treatment device1710 is shown inFIG. 17D. In this embodiment, the treatment assembly1721 includes atubular support structure1722 having a proximal portion that extends proximally into the elongated shaft to carry the energy supply wires for the energy delivery elements1724 disposed about thesupport structure1722. Extending parallel to the proximal portion of thetubular support structure1722 are acontrol member1768 that includes a push-pull rod. Also preferably extending parallel to the push-pull control member1768 is atubular member1780 defining an internal lumen for passage of aguide wire1766. Each of the distal end region1722aof thesupport structure1722 and the pull-push rod member1768 is preferably affixed to thetubular member1780 such that axial movement of the push-pull member1768 moves the distal end of thetubular support structure1722 and thetubular member1780 along theguide wire1766. Thetubular support structure1722 is preferably helically wrapped about thetubular member1780 such that thetubular member1780 is internal to the helix defined by thesupport member1722. The distal and proximal movement of the distal region1722arespectively extends and reduces the axial length of the helicaltubular support structure1722 to place the treatment assembly1721 in the delivery and deployed configurations. Proximal of the treatment assembly1721, distal of the handle assembly along thetubular member1780 is an opening1782 to provide for a rapid exchange configuration.
• Because the push-pull member1768 and the distal end1722aof the tubular support structure are affixed to thetubular member1780, thetubular support structure1722 cannot be rotated about thetubular member1780 and its axial opening through which the guide wire passes. Accordingly, to provide for a distal end1722athat rotates about the guide wire lumen of themember1780, the push-pull member1768 and the distal end1722aof the tubular support member1722aare coupled to but separable from thetubular member1780 as seen for example, inFIG. 17E. More specifically thetubular member1780 is preferably detachable or independently rotatable with respect to thetubular support structure1722 and the push-pull member1768. Accordingly, a rotatable distal region of the treatment assembly1721 is rotatable about theguide wire1766. Moreover, because the distal region of the treatment assembly1721 is rotatable about thetubular member1780, the proximal guide wire exit1782 can remain fixed relative to the treatment assembly1721 such that the rapid exchange configuration does not interfere with rotation of the treatment assembly.
• In the embodiment shown inFIG. 17E, asleeve1785 is provided to which the distal end of thetubular support structure1722 and the push-pull member1768 are affixed. Thesleeve1785 further defines an internal passage for slidably receiving themember1780. Thesleeve1785 provides for a tip assembly of the treatment assembly which axially slides and rotates about thetubular member1780. The configuration further provides rotation of thesupport structure1722 and the push-pull member1768 of the assembly relative to thetubular member1780 while maintaining the preferably generally helical shape without thesupport structure1722 “wrapping up” around thetubular member1780 and losing the desired shape/configuration while manipulating the treatment assembly within the vessel.
IV. APPLYING ENERGY TO TISSUE VIA THE ENERGY DELIVERY ELEMENT
• Referring back toFIG. 1, theenergy generator26 may supply a continuous or pulsed RF electric field to theenergy delivery elements24. Although a continuous delivery of RF energy is desirable, the application of RF energy in pulses may allow the application of relatively higher energy levels (e.g., higher power), longer or shorter total duration times, and/or better controlled intravascular renal neuromodulation therapy. Pulsed energy may also allow for the use of a smaller electrode.
• Although many of the embodiments described herein pertain to electrical systems configured for the delivery of RF energy, it is contemplated that the desired treatment may be accomplished by other means, e.g., by coherent or incoherent light; direct thermal modification (e.g., with a heated or cooled fluid or resistive heating element or cryogenic applicator); microwave; ultrasound (including high intensity focused ultrasound); diode laser; radiation; a tissue heating fluid; and/or a cryogenic refrigerant.
• As previously discussed, energy delivery may be monitored and controlled via data collected with one or more sensors, such as temperature sensors (e.g., thermocouples, thermistors, etc.), impedance sensors, pressure sensors, optical sensors, flow sensors, chemical sensors, etc., which may be incorporated into or on theenergy delivery elements24, thesupport structure22, and/or in/on adjacent areas on thedistal portion20. A sensor may be incorporated into the energy delivery element(s)24 in a manner that specifies whether the sensor(s) are in contact with tissue at the treatment site and/or are facing blood flow. The ability to specify sensor placement relative to tissue and blood flow is highly significant, since a temperature gradient across the electrode from the side facing blood flow to the side in contact with the vessel wall may be up to about 15° C. Significant gradients across the electrode in other sensed data (e.g., flow, pressure, impedance, etc.) also are expected.
• The sensor(s) may, for example, be incorporated on the side of one or moreenergy delivery elements24 that contact the vessel wall at the treatment site during power and energy delivery or may be incorporated on the opposing side of one or moreenergy delivery elements24 that face blood flow during energy delivery, and/or may be incorporated within certain regions of the energy delivery elements24 (e.g., distal, proximal, quandrants, etc.). In some embodiments, multiple sensors may be provided at multiple positions along the electrode or energy delivery element array and/or relative to blood flow. For example, a plurality of circumferentially and/or longitudinally spaced sensors may be provided. In one embodiment, a first sensor may contact the vessel wall during treatment, and a second sensor may face blood flow.
• Additionally or alternatively, various microsensors may be used to acquire data corresponding to theenergy delivery elements24, the vessel wall and/or the blood flowing across theenergy delivery elements24. For example, arrays of micro thermocouples and/or impedance sensors may be implemented to acquire data along theenergy delivery elements24 or other parts of the treatment device. Sensor data may be acquired or monitored prior to, simultaneous with, or after the delivery of energy or in between pulses of energy, when applicable. The monitored data may be used in a feedback loop to better control therapy, e.g., to determine whether to continue or stop treatment, and it may facilitate controlled delivery of an increased or reduced power or a longer or shorter duration therapy.
V. BLOOD FLOW AROUND THE ENERGY DELIVERY ELEMENTS
• Non-target tissue may be protected by blood flow within the respective renal artery that serves as a conductive and/or convective heat sink that carries away excess thermal energy. For example, referring toFIGS. 1 and 18 together, since blood flow is not blocked by theelongated shaft16, the helically-shapedtherapeutic assembly21, and theenergy delivery elements24 it carries, the native circulation of blood in the respective renal artery serves to remove excess thermal energy from the non-target tissue and the energy delivery element. The removal of excess thermal energy by blood flow also allows for treatments of higher power, where more power may be delivered to the target tissue as thermal energy is carried away from the electrode and non-target tissue. In this way, intravascularly-delivered thermal energy heats target neural fibers located proximate to the vessel wall to modulate the target neural fibers, while blood flow within the respective renal artery protects non-target tissue of the vessel wall from excessive or undesirable thermal injury.
• It may also be desirable to provide enhanced cooling by inducing additional native blood flow across theenergy delivery elements24. For example, techniques and/or technologies may be implemented by the clinician to increase perfusion through the renal artery or to theenergy delivery elements24 themselves. These techniques include positioning partial occlusion elements (e.g., balloons) within upstream vascular bodies such as the aorta, or within a portion of the renal artery to improve flow across the energy delivery element.
• FIG. 18, for example, illustrates hypothetical blood flow in a renal artery. Blood flow (F) is thought to be laminar, e.g., to exhibit a gradient of flow rates such that in an area closest to the center of the artery, e.g.,area2214, the blood flow F may be faster relative to areas closer to therenal artery wall55, e.g.,areas2215. Accordingly, the blood flow F nearest the location of theenergy delivery elements24 is relatively slow. Because cooling of theenergy delivery elements24 is mediated by blood flow, improved cooling may be achieved by redirecting the blood flow F in the renal artery so that the blood flowing around theenergy delivery elements24 is relatively faster.
• FIG. 19A illustrates an embodiment in which afluid redirecting element2220 is positioned within the center of the renal artery. Accordingly, the flowing blood, represented byarrows2216, including faster flowing blood, is redirected towards theenergy delivery elements24. The fluid redirecting element may be any biocompatible material, such as a polymer, that is positioned to encourage blood flow towards theenergy delivery elements24 carried by amesh structure3422.
• Referring toFIGS. 19A and 19B together, thefluid redirecting element2220 may extend from thedistal end region20 of theelongated shaft16, generally along the axis A-A of theelongated shaft16. For embodiments in which a guide wire (not shown) is used, thefluid redirecting element2220 may include an integral passage (not shown) of an inner member sized and shaped to accommodate the guide wire. In addition, in some embodiments, an axial length of thefluid redirecting element2220 may be at least 25%, at least 50%, or at least 75% of an axial length of themesh structure2220 in the expanded configuration. In any case, in order to maximize redirected blood flow, thefluid redirecting element2220 may extend at least far enough into themesh structure3422 so that an imaginary axis through theenergy delivery elements24 and orthogonal to the axis A-A intersects thefluid redirecting element2220. Thediameter2228 of thefluid redirecting element2220 may be expandable such that in its unexpanded state it is generally compatible with insertion, repositioning, and removal of themesh structure3422 and in its expanded state it is configured to redirect blood flow toward areas closer to the renal artery wall, e.g.,areas2215. As shown inFIG. 19B, in a collapsed configuration, themesh structure3422 may conform to the shape of thefluid redirecting element2220. Thediameter2228 may be slightly larger than, about equal to, or less than a diameter of theelongated shaft16. In one embodiment, thediameter2228 may be less than about 2.18 mm.
• In addition, or as an alternative, to passively utilizing blood flow as a heat sink, active cooling may be provided to remove excess thermal energy and protect non-target tissues. For example, a thermal fluid infusate may be injected, infused, or otherwise delivered into the vessel in an open circuit system. Thermal fluid infusates used for active cooling may, for example, include (room temperature or chilled) saline or some other biocompatible fluid. The thermal fluid infusate(s) may, for example, be introduced through thetreatment device12 via one or more infusion lumens and/or ports. When introduced into the bloodstream, the thermal fluid infusate(s) may, for example, be introduced through a guide catheter at a location upstream from theenergy delivery elements24 or at other locations relative to the tissue for which protection is sought. The delivery of a thermal fluid infusate in the vicinity of the treatment site (via an open circuit system and/or via a closed circuit system) may, for example, allow for the application of increased/higher power treatment, may allow for the maintenance of lower temperature at the vessel wall during energy delivery, may facilitate the creation of deeper or larger lesions, may facilitate a reduction in treatment time, may allow for the use of a smaller electrode size, or a combination thereof.
• Accordingly, treatment devices configured in accordance with embodiments of the technology may include features for an open circuit cooling system, such as a lumen in fluid communication with a source of infusate and a pumping mechanism (e.g., manual injection or a motorized pump) for injection or infusion of saline or some other biocompatible thermal fluid infusate from outside the patient, throughelongated shaft16 and towards theenergy delivery elements24 into the patient's bloodstream during energy delivery. In addition, thedistal end region20 of theelongated shaft16 may include one or more ports for injection or infusion of saline directly at the treatment site.
VI. USE OF THE SYSTEM
• A. Intravascular Delivery, Deflection and Placement of the Treatment Device
• As mentioned previously, any one of the embodiments of the treatment devices described herein may be delivered using OTW or RX techniques. When delivered in this manner, theelongated shaft16 includes a passage or lumen accommodating passage of a guide wire. Alternatively, any one of thetreatment devices12 described herein may be deployed using a conventional guide catheter or pre-curved renal guide catheter (e.g., as shown inFIGS. 3A and 3B). When using a guide catheter, the femoral artery is exposed and cannulated at the base of the femoral triangle, using conventional techniques. In one exemplary approach, a guide wire is inserted through the access site and passed using image guidance through the femoral artery, into the iliac artery and aorta, and into either the left or right renal artery. A guide catheter may be passed over the guide wire into the accessed renal artery. The guide wire is then removed. Alternatively, a renal guide catheter, which is specifically shaped and configured to access a renal artery, may be used to avoid using a guide wire. Still alternatively, the treatment device may be routed from the femoral artery to the renal artery using angiographic guidance and without the need of a guide catheter.
• When a guide catheter is used, at least three delivery approaches may be implemented. In one approach, one or more of the aforementioned delivery techniques may be used to position a guide catheter within the renal artery just distal to the entrance of the renal artery. The treatment device is then routed via the guide catheter into the renal artery. Once the treatment device is properly positioned within the renal artery, the guide catheter is retracted from the renal artery into the abdominal aorta. In this approach, the guide catheter should be sized and configured to accommodate passage of the treatment device. For example, a 6 French guide catheter may be used.
• In a second approach, a first guide catheter is placed at the entrance of the renal artery (with or without a guide wire). A second guide catheter (also called a delivery sheath) is passed via the first guide catheter (with or without the assistance of a guide wire) into the renal artery. The treatment device is then routed via the second guide catheter into the renal artery. Once the treatment device is properly positioned within the renal artery the second guide catheter is retracted, leaving the first guide catheter at the entrance to the renal artery. In this approach the first and second guide catheters should be sized and configured to accommodate passage of the second guide catheter within the first guide catheter (i.e., the inner diameter of the first guide catheter should be greater than the outer diameter of the second guide catheter). For example, a 8 French guide catheter may be used for the first guide catheter, and 5 French guide catheter may be used for the second guide catheter.
• In a third approach, a renal guide catheter is positioned within the abdominal aorta, just proximal to the entrance of the renal artery. Thetreatment device12 as described herein is passed through the guide catheter and into the accessed renal artery. The elongated shaft makes atraumatic passage through the guide catheter, in response to forces applied to theelongated shaft16 through thehandle assembly34.
• B. Control of Applied Energy
• 1. Overview
• Referring back toFIG. 1, a treatment administered using thesystem10 constitutes delivering energy through the energy delivery elements orelectrodes24 to the inner wall of a renal artery for a predetermined amount of time (e.g., 120 sec). Multiple treatments (e.g., 4-6) may be administered in both the left and right renal arteries to achieve the desired coverage. A technical objective of a treatment may be, for example, to heat tissue to a desired depth (e.g., at least about 3 mm) to a temperature that would lesion a nerve (e.g., about 65° C.). A clinical objective of the procedure typically is to neuromodulate (e.g., lesion) a sufficient number of renal nerves (either efferent or afferent nerves of the sympathetic renal plexus) to cause a reduction in sympathetic tone. If the technical objective of a treatment is met (e.g., tissue is heated to about 65° C. to a depth of about 3 mm) the probability of forming a lesion of renal nerve tissue is high. The greater the number of technically successful treatments, the greater the probability of modulating a sufficient proportion of renal nerves, and thus the greater the probability of clinical success.
• Throughout the treatment there may be a number of states that are indicative of a possibility that the treatment may not be successful. In certain embodiments, based on indications of these states, the operation of thesystem10 may be stopped or modified. For example, certain indications may result in cessation of energy delivery and an appropriate message may be displayed, such as ondisplay33. Factors that may result in a display message and/or cessation or modification of a treatment protocol include, but are not limited to, indications of an impedance, blood flow, and/or temperature measurement or change that is outside of accepted or expected thresholds and/or ranges that may be predetermined or calculated. A message can indicate information such as a type of patient condition (e.g., an abnormal patient condition), the type and/or value of the parameter that falls outside an accepted or expected threshold, an indication of suggested action for a clinician, or an indication that energy delivery has been stopped. However, if no unexpected or aberrant measurements are observed, energy may continue to be delivered at the target site in accordance with a programmed profile for a specified duration resulting in a complete treatment. Following a completed treatment, energy delivery is stopped and a message indicating completion of the treatment may be displayed.
• However, a treatment can be completed without initiating an indication of an abnormal patient condition and yet an event or combination of events could occur that alters (e.g., decreases) the probability of a technically successful treatment. For example, an electrode that is delivering energy could move or be inadvertently placed with insufficient contact between the electrode and the wall of a renal artery, thereby resulting in insufficient lesion depth or temperature. Therefore, even when a treatment is completed without an indication of abnormal patient condition, it may be difficult to evaluate the technical success of the treatment. Likewise, to the extent that indications of abnormal patient conditions may be reported by thesystem10, it may be difficult to understand the causes of the abnormal patient conditions (such as temperature and/or impedance values that fall outside of expected ranges).
• As noted above, one or more evaluation/feedback algorithms31 may be provided that are executed on a processor-based component of thesystem10, such as one or more components provided with thegenerator26. In such implementations, the one or more evaluation/feedback algorithms31 may be able to provide a user with meaningful feedback that can be used in evaluating a given treatment and/or that can be used in learning the significance of certain types of abnormal patient conditions and how to reduce the occurrence of such conditions. For example, if a particular parameter (e.g., an impedance or temperature value) causes or indicates that treatment did not proceed as expected and (in some instances), may have resulted in a technically unsuccessful treatment, thesystem10 can provide feedback (e.g., via the display33) to alert the clinician. The alert to the clinician can range from a simple notification of unsuccessful treatment to a recommendation that a particular parameter of the treatment (e.g., the impedance value(s) during treatment, placement of theenergy delivery elements24 within the patient, etc.) be modified in a subsequent treatment. Thesystem10 can accordingly learn from completed treatment cycles and modify subsequent treatment parameters based on such learning to improve efficacy. Non-exhaustive examples of measurements the one or more evaluation/feedback algorithms31 may consider include measurements related to change(s) in temperature over a specified time, a maximum temperature, a maximum average temperature, a minimum temperature, a temperature at a predetermined or calculated time relative to a predetermined or calculated temperature, an average temperature over a specified time, a maximum blood flow, a minimum blood flow, a blood flow at a predetermined or calculated time relative to a predetermined or calculated blood flow, an average blood flow over time, a maximum impedance, a minimum impedance, an impedance at a predetermined or calculated time relative to a predetermined or calculated impedance, a change in impedance over a specified time, or a change in impedance relative to a change in temperature over a specified time. Measurements may be taken at one or more predetermined times, ranges of times, calculated times, and/or times when or relative to when a measured event occurs. It will be appreciated that the foregoing list merely provides a number of examples of different measurements, and other suitable measurements may be used.
• 2. Control of Applied Energy
• With the treatments disclosed herein for delivering therapy to target tissue, it may be beneficial for energy to be delivered to the target neural structures in a controlled manner. The controlled delivery of energy will allow the zone of thermal treatment to extend into the renal fascia while reducing undesirable energy delivery or thermal effects to the vessel wall. A controlled delivery of energy may also result in a more consistent, predictable and efficient overall treatment. Accordingly, thegenerator26 desirably includes a processor including a memory component with instructions for executing an algorithm30 (seeFIG. 1) for controlling the delivery of power and energy to the energy delivery device. Thealgorithm30, a representative embodiment of which is depicted inFIG. 3, may be implemented as a conventional computer program for execution by a processor coupled to thegenerator26. A clinician using step-by-step instructions may also implement thealgorithm30 manually.
• The operating parameters monitored in accordance with the algorithm may include, for example, temperature, time, impedance, power, blood flow, flow velocity, volumetric flow rate, blood pressure, heart rate, etc. Discrete values in temperature may be used to trigger changes in power or energy delivery. For example, high values in temperature (e.g., 85° C.) could indicate tissue desiccation in which case the algorithm may decrease or stop the power and energy delivery to prevent undesirable thermal effects to target or non-target tissue. Time additionally or alternatively may be used to prevent undesirable thermal alteration to non-target tissue. For each treatment, a set time (e.g., 2 minutes) is checked to prevent indefinite delivery of power.
• Impedance may be used to measure tissue changes. Impedance indicates the electrical property of the treatment site. In thermal inductive embodiments, when an electric field is applied to the treatment site, the impedance will decrease as the tissue cells become less resistive to current flow. If too much energy is applied, tissue desiccation or coagulation may occur near the electrode, which would increase the impedance as the cells lose water retention and/or the electrode surface area decreases (e.g., via the accumulation of coagulum). Thus, an increase in tissue impedance may be indicative or predictive of undesirable thermal alteration to target or non-target tissue. In other embodiments, the impedance value may be used to assess contact of the energy delivery element(s)24 with the tissue. For multiple electrode configurations (e.g., when the energy delivery element(s)24 includes two or more electrodes,) a relatively small difference between the impedance values of the individual electrodes may be indicative of good contact with the tissue. For a single electrode configuration, a stable value may be indicative of good contact. Accordingly, impedance information from the one or more electrodes may be provided to a downstream monitor, which in turn may provide an indication to a clinician related to the quality of the energy delivery element(s)24 contact with the tissue.
• Additionally or alternatively, power is an effective parameter to monitor in controlling the delivery of therapy. Power is a function of voltage and current. Thealgorithm30 may tailor the voltage and/or current to achieve a desired power.
• Derivatives of the aforementioned parameters (e.g., rates of change) also may be used to trigger changes in power or energy delivery. For example, the rate of change in temperature could be monitored such that power output is reduced in the event that a sudden rise in temperature is detected. Likewise, the rate of change of impedance could be monitored such that power output is reduced in the event that a sudden rise in impedance is detected.
• As seen inFIG. 20, when a clinician initiates treatment (e.g., via thefoot pedal32 illustrated inFIG. 1), thecontrol algorithm30 includes instructions to thegenerator26 to gradually adjust its power output to a first power level P₁(e.g., 5 watts) over a first time period t₁(e.g., 15 seconds). The power increase during the first time period is generally linear. As a result, thegenerator26 increases its power output at a generally constant rate of P₁/t₁. Alternatively, the power increase may be non-linear (e.g., exponential or parabolic) with a variable rate of increase. Once P₁and t₁are achieved, the algorithm may hold at P₁until a new time t₂for a predetermined period of time t₂−t₁(e.g., 3 seconds). At t₂power is increased by a predetermined increment (e.g., 1 watt) to P₂over a predetermined period of time, t₃−t₂(e.g., 1 second). This power ramp in predetermined increments of about 1 watt over predetermined periods of time may continue until a maximum power P_MAXis achieved or some other condition is satisfied. In one embodiment, P_MAXis 8 watts. In another embodiment P_MAXis 10 watts. Optionally, the power may be maintained at the maximum power P_MAXfor a desired period of time or up to the desired total treatment time (e.g., up to about 120 seconds).
• InFIG. 20, thealgorithm30 illustratively includes a power-control algorithm. However, it should be understood that thealgorithm30 alternatively may include a temperature-control algorithm. For example, power may be gradually increased until a desired temperature (or temperatures) is obtained for a desired duration (or durations). In another embodiment, a combination power-control and temperature-control algorithm may be provided.
• As discussed, thealgorithm30 includes monitoring certain operating parameters (e.g., temperature, time, impedance, power, flow velocity, volumetric flow rate, blood pressure, heart rate, etc.). The operating parameters may be monitored continuously or periodically. Thealgorithm30 checks the monitored parameters against predetermined parameter profiles to determine whether the parameters individually or in combination fall within the ranges set by the predetermined parameter profiles. If the monitored parameters fall within the ranges set by the predetermined parameter profiles, then treatment may continue at the commanded power output. If monitored parameters fall outside the ranges set by the predetermined parameter profiles, thealgorithm30 adjusts the commanded power output accordingly. For example, if a target temperature (e.g., 65° C.) is achieved, then power delivery is kept constant until the total treatment time (e.g., 120 seconds) has expired. If a first temperature threshold (e.g., 70° C.) is achieved or exceeded, then power is reduced in predetermined increments (e.g., 0.5 watts, 1.0 watts, etc.) until a target temperature is achieved. If a second power threshold (e.g., 85° C.) is achieved or exceeded, thereby indicating an undesirable condition, then power delivery may be terminated. The system may be equipped with various audible and visual alarms to alert the operator of certain conditions.
• The following is a non-exhaustive list of events under whichalgorithm30 may adjust and/or terminate/discontinue the commanded power output:
• (1) The measured temperature exceeds a maximum temperature threshold (e.g., from about 70 to about 85° C.).
• (2) The average temperature derived from the measured temperature exceeds an average temperature threshold (e.g., about 65° C.).
• (3) The rate of change of the measured temperature exceeds a rate of change threshold.
• (4) The temperature rise over a period of time is below a minimum temperature change threshold while thegenerator26 has non-zero output. Poor contact between the energy delivery element(s)24 and the arterial wall may cause such a condition.
• (5) A measured impedance exceeds or falls outside an impedance threshold (e.g., <20 Ohms or >500 Ohms).
• (6) A measured impedance exceeds a relative threshold (e.g., impedance decreases from a starting or baseline value and then rises above this baseline value)
• (7) A measured power exceeds a power threshold (e.g., >8 Watts or >10 Watts).
• (8) A measured duration of power delivery exceeds a time threshold (e.g., >120 seconds).
• Advantageously, the magnitude of maximum power delivered during renal neuromodulation treatment in accordance with the present technology may be relatively low (e.g., less than about 15 Watts, less than about 10 Watts, less than about 8 Watts, etc.) as compared, for example, to the power levels utilized in electrophysiology treatments to achieve cardiac tissue ablation (e.g., power levels greater than about 15 Watts, greater than about 30 Watts, etc.). Since relatively low power levels may be utilized to achieve such renal neuromodulation, the flow rate and/or total volume of intravascular infusate injection needed to maintain the energy delivery element and/or non-target tissue at or below a desired temperature during power delivery (e.g., at or below about 50° C., for example, or at or below about 45° C.) also may be relatively lower than would be required at the higher power levels used, for example, in electrophysiology treatments (e.g., power levels above about 15 Watts). In embodiments in which active cooling is used, the relative reduction in flow rate and/or total volume of intravascular infusate infusion advantageously may facilitate the use of intravascular infusate in higher risk patient groups that would be contraindicated were higher power levels and, thus, correspondingly higher infusate rates/volumes utilized (e.g., patients with heart disease, heart failure, renal insufficiency and/or diabetes mellitus).
• C. Technical Evaluation of a Treatment
• FIG. 21 is a block diagram of atreatment algorithm2180 configured in accordance with an embodiment of the present technology. Thealgorithm2180 is configured to evaluate events in a treatment, determine the probability of technical success of the treatment and display a message accordingly to provide feedback to an operator of the system10 (or another suitable treatment system). If the treatment is determined to have a predetermined probability of sub optimal technical success, a message indicating that the treatment did not proceed as expected may be displayed. Alternative implementations can categorize a treatment into several ranges of probabilities of success, such as probability of success on a scale of 1 to 5. Similarly, in certain implementations, thealgorithm2180 can evaluate if a treatment belongs in a high probability of success category, a very low probability of success category, or somewhere in between.
• Variables that characterize a treatment and that may be used by thealgorithm2180 in evaluating a treatment include, but are not limited to: time (i.e., treatment duration), power, change in temperature, maximum temperature, mean temperature, blood flow, standard deviation of temperature or impedance, change in impedance, or combinations of these or other variables. For example, some or all of the variables may be provided to thealgorithm2180 astreatment data2182. In this generalized depiction of analgorithm2180, thetreatment data2180 may be assessed based on a cascade or series of different categories or degrees ofcriteria2184. Favorable assessment of thetreatment data2182 in view of one of thecriteria2184 may result in the display (block2186) of a message indicating the treatment was acceptable or successful. Failure of thetreatment data2182 to be found acceptable in view of acriterion2184 may result in the treatment data dropping to thenext evaluation criterion2184.
• In the depicted embodiment, failure of the treatment data to be found acceptable in view of all of thecriteria2184 may result in an additional evaluation being performed, such as the depicted analysis andscoring step2188. The output of the analysis and scoring step (e.g., a score2190) may be evaluated (block2192). Based on thisevaluation2192, the treatment may be deemed acceptable, and the corresponding screen displayed (block2186), or not acceptable, and ascreen2194 displayed indicating that treatment did not proceed as expected. In still further embodiments, thealgorithm2180 can include an automatic action (e.g., automatic reduction of the power level supplied to the energy source) in response to an indication that treatment did not proceed as expected.
• WhileFIG. 21 depicts a generalized and simplified implementation of a treatment evaluation algorithm,FIG. 22 depicts a more detailed example of one embodiment of atreatment evaluation algorithm2200. Thetreatment evaluation algorithm2200 may be computed following the completion of a treatment (block2202), which may be 120 seconds long (as depicted) or some other suitable duration, and using data and/or measurements derived over the course of the treatment.
• In the depicted embodiment, it is considered likely that the greatest probability of less than ideal treatment occurs when an electrode is not in consistent contact with the vessel wall. Accordingly, decision blocks2204,2206,2208, and2210 in the flowchart are associated with different criteria and screen out those treatments that appear to have one or more criteria outside a pre-determined range (i.e., do not have a high probability of success) based on observed or measureddata2202 over the course of the completed treatment. In the depicted embodiment, those treatments that are not screened out at decision blocks2204,2206,2208, and2210 enter a linear discriminant analysis (LDA)2212 to further evaluate the treatment. In other embodiments, other suitable analyses may be performed instead of the depicted LDA. Values assigned to each step (i.e., evaluation by a respective criterion) andcoefficients2214 used in the LDA can be derived from data collected from several treatments and/or from experience gained from animal studies.
• In the depicted embodiment, thefirst decision block2204 evaluates the initial temperature response to energy delivery by checking if the change in average temperature in the first 15 seconds is greater than 14° C. In one implementation, average temperature refers to the average over a short amount of time (e.g., 3 seconds), which essentially filters large fluctuations at high frequency caused by pulsatile blood flow. As will be appreciated, a temperature rise in the treatment electrode is a result of heat conducting from tissue to the electrode. If an electrode is not in sufficient contact with a vessel wall, energy is delivered into the blood flowing around it and the temperature of the electrode is not increased as much. With this in mind, if the change in average temperature in the first 15 seconds is greater than, e.g., 14° C., this initial temperature response may indicate sufficient electrode contact, contact force, and/or blood flow rate, at least in the beginning of the treatment and, if no indication that treatment did not proceed as expected is encountered for the remainder of the treatment, there is not a high probability that the treatment was less than optimal or technically unsuccessful. Thus, a positive answer atdecision block2204 results in a “Treatment Complete”message2220 being displayed. However, if the change in average temperature in the first 15 seconds is less than or equal to, e.g., 14° C., this initial temperature response may indicate that the electrode may not have had sufficient contact with the vessel wall. Thus, a negative answer atdecision block2204 results in proceeding tocriteria2206 for further evaluation.
• Atdecision block2206 the hottest temperature is evaluated by checking if the maximum average temperature is greater than, e.g., 56° C. A temperature rise above a threshold level (e.g., 56° C.), regardless of duration, may be enough to allow technical success. Thus, a temperature above threshold may be sufficient to indicate successful lesion formation despite the fact that atdecision block2204 the initial rise in temperature did not indicate sufficient contact. For example, the electrode may not have had sufficient contact initially but then contact could have been made at least for enough time to cause the vessel wall to heat up such that the temperature sensor in the electrode reads above 56° C. A positive result atdecision block2206 results in a “Treatment Complete”message2220 being displayed. However, a negative result atdecision block2206 indicates that the maximum average temperature did not rise enough. Thealgorithm2200, therefore, proceeds todecision block2208 for further evaluation.
• Atdecision block2208 the mean temperature is evaluated during a period when power is sustained at its maximum amount (i.e., the ramping up period is eliminated from the mean calculation). In one embodiment, this evaluation consists of determining whether the mean real time temperature is above 53° C. during the period from 45 seconds to 120 seconds. In this manner, this criterion checks to determine if temperature was above a threshold for a certain duration. Ifdecision block2208 yields a positive determination then, despite the fact that the initial temperature response and the maximum average temperature were insufficient to indicate technical success (i.e., decision blocks2204 and2206 were failed), the mean temperature during the last 75 seconds indicates sufficient contact for sufficient time. For example, it is possible that a sufficient lesion was made and yet the maximum average temperature measured in the electrode was not greater than 56° C. because there is high blood flow pulling heat from the electrode. Therefore, a positive result atdecision block2208 results in a “Treatment Complete”message2220 being displayed. However, a negative result atdecision block2208 indicates that the mean real time temperature in the sustained power stage was not sufficient and thealgorithm2200 proceeds todecision block2210 for further evaluation of the treatment.
• Atdecision block2210 the change in impedance is evaluated by checking if the percentage of impedance change during a predetermined period of time (e.g., 45 seconds to 114 seconds), is greater than a predetermined value (e.g., 14%) of the initial impedance. The initial impedance is determined as the impedance shortly after the beginning of treatment (e.g., at 6 seconds) to eliminate possible misreadings in impedance measurement prior to this period (e.g., due to contrast injection). As will be appreciated, the impedance of tissue to radiofrequency (RF) electrical current decreases as the tissue temperature increases until the tissue is heated enough to cause it to desiccate at which point its impedance starts to rise. Therefore, a decrease in tissue impedance can indicate a rise in tissue temperature. The percentage change in real time impedance over the sustained power stage may be calculated as follows:
• $\begin{array}{cc}\%\Delta Z\mathrm{over}\mathrm{SS}=100*\left(\frac{{\mathrm{<figure-callout\; label="Z"\; filenames="US20120116382A1-20120510-D00041.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{6s}^{\mathrm{avg}}-\left(\mathrm{mean}\mathrm{RT}Z\mathrm{over}\mathrm{SS}\right)}{{\mathrm{<figure-callout\; label="Z"\; filenames="US20120116382A1-20120510-D00041.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{6s}^{\mathrm{avg}}}\right)& \left(1\right)\end{array}$
• Ifdecision block2210 yields a positive determination then, despite the fact that the previous three decision blocks failed to show that there was a sufficient rise in temperature (i.e., decision blocks2204,2206, and2208 were failed), the change in impedance could indicate that tissue was heated sufficiently but the temperature sensor in the electrode did not rise enough. For example, very high blood flow could cause the electrode temperature to remain relatively low even if the tissue was heated. Therefore, a positive result atdecision block2210 results in a “Treatment Complete”message2220 being displayed. However, a negative result atdecision block2210 results in thealgorithm2200 proceeding to perform aLDA2212.
• AtLDA2212, a combination of events is evaluated along with a rating of importance for each event. In the depicted embodiment, for example, the criteria evaluated at decision blocks2204,2206,2208,2210 are included in theLDA2212. In addition, in this implementation, three additional criteria may be included: (1) standard deviation of average temperature (which can provide an indication of the degree of sliding motion caused by respiration); (2) standard deviation of real time temperature (which can provide an indication of variable blood flow and/or contact force and/or intermittent contact); and (3) adjusted change in average impedance at the end of the treatment (which can further characterize change in impedance and provide an indication of change in temperature of tissue). If this analysis determines the combination of variables to have a significant impact on reducing technical success (e.g., a LDA score <0 at decision block2222) then an “Unexpected Treatment”message2224 is displayed. Otherwise, a “Treatment Complete”message2220 is displayed.
• It will be appreciated that the various parameters described above are merely representative examples associated with one embodiment of thealgorithm2200, and one or more of these parameters may vary in other embodiments. Further, the specific values described above with respect to particular portions of the treatment may be modified/changed in other embodiments based on, for example, different device configurations, electrode configurations, treatment protocols, etc.
• As described above, thealgorithm2200 is configured to evaluate a treatment and display a message indicating that treatment is complete or, alternatively, that treatment did not proceed as expected. Based on the message describing the evaluation of the treatment, the clinician (or the system using automated techniques) can then decide whether further treatments may be necessary and/or if one or more parameters should be modified in subsequent treatments. In the above-described examples, for example, thealgorithm2200 may evaluate a number of situations generally related to poor contact between the electrode and vessel wall to help determine if the treatment was less than optimal. For example, poor contact may occur when an electrode slides back and forth as the patient breaths and the artery moves, when an electrode becomes displaced when a patient moves, when the catheter is moved inadvertently, when a catheter is not deflected to the degree needed to apply sufficient contact or contact force between the electrode and vessel wall, and/or when an electrode is placed in a precarious position. Further, as described above, if a particular parameter or set of parameters may have contributed to or resulted in a less than optimal treatment, the system10 (FIG. 1) can provide feedback to alert the clinician to modify one or more treatment parameters during a subsequent treatment. Such evaluation and feedback of a treatment is expected to help clinicians learn to improve their placement technique to get better contact and reduce the frequency of technically unsuccessful treatments.
• D. Feedback Related to High Temperature Conditions
• While the preceding describes generalized evaluation of the technical success of a treatment, another form of feedback that may be useful to an operator of the system10 (FIG. 1) is feedback related to specific types of patient or treatment conditions. For example, thesystem10 may generate a message related to high temperature conditions. In particular, during a treatment while energy is being delivered, tissue temperature may increase above a specified level. A temperature sensor (e.g., thermocouple, thermistor, etc.) positioned in or near the electrode provides an indication of temperature in the electrode and, to some extent, an indication of tissue temperature. The electrode does not heat directly as energy is delivered to tissue. Instead, tissue is heated and the heat conducts to the electrode and the temperature sensor in the electrode. In one implementation, thesystem10 may cease energy delivery if the real time temperature rises above a predefined maximum temperature (e.g., 85° C.). In such an event, the system may generate a message indicating the high temperature condition. However, depending on the circumstances, different actions by the clinician may be appropriate.
• If tissue becomes too hot, established temperature thresholds can be exceeded. The implications of high tissue temperature are that an acute constriction of the artery or a protrusion of the artery wall could occur. This can happen right away or within a short time (e.g., about 50 seconds to about 100 seconds) after the occurrence of the high temperature is noted and a message is generated. In such an occurrence, the clinician may be instructed to image the treatment site to watch for a constriction or protrusion before starting another treatment.
• FIG. 23, for example, is a block diagram illustrating analgorithm2250 for providing operator feedback when a high temperature condition is detected in accordance with an embodiment of the present technology. In one implementation thealgorithm2250 is executed in response to a high temperature condition (block2252) and evaluates (decision block2254) data from the treatment to determine if the high temperature condition involved a situation that included sudden instability or if it did not. Sudden instability can be caused, for example, by sudden movement of the patient or catheter, thereby causing the electrode to be pushed harder (i.e., contact force is increased) into the vessel wall, which could also be accompanied by movement to another location. In the event that sudden instability is not detected atdecision block2254, a first message may be displayed (block2256), such as an indication that a high temperature has been detected and an instruction to image the treatment site to determine if the site has been damaged. In the event that sudden instability is detected atdecision block2254, an alternative message may be displayed (block2258) that, in addition to indicating the occurrence of the high temperature and instructing the clinician to image the treatment site, may also indicate the possibility that the electrode may have moved from its original site. Such feedback may prompt the clinician to compare previous images and avoid treating again on either of the original site or the site to which the electrode has moved.
• E. Feedback Related to High Impedance
• As with high temperature, in certain circumstances the system10 (FIG. 1) may generate a message related to the occurrence of high impedance. As will be appreciated, impedance to RF current passing from a treatment electrode through the body to a dispersive return electrode can provide an indication of characteristics of the tissue that is in contact with the treatment electrode. For example, an electrode positioned in the blood stream in a renal artery may measure a lower impedance than an electrode contacting the vessel wall. Furthermore, as tissue temperature rises its impedance decreases. However, if the tissue gets too hot it may desicate and its impedance may increase. During a treatment as tissue is gradually heated it is expected that impedance will decrease. A significant rise in impedance can be a result of an undesired situation such as tissue desication or electrode movement. In certain implementations, thesystem10 may be configured to cease energy delivery if the real time impedance rise is higher than a predefined maximum change in impedance from the starting impedance.
• FIG. 24, for example, is a block diagram illustrating analgorithm2270 for providing operator feedback upon occurrence of a high impedance condition in accordance with an embodiment of the present technology. In the depicted embodiment, thealgorithm2270 evaluates data from the treatment and determines if detection of a high impedance event (block2272) was likely to involve a situation in which (a) tissue temperature was high and desiccation was likely, (b) the electrode moved, or (c) there was poor electrode contact or no electrode contact with the vessel wall. Thealgorithm170 evaluates the data to determine which, if any, of these three situations occurred and displays one of threemessages2274,2276, or2278 accordingly.
• In accordance with one embodiment of thealgorithm2270, upon detection of a high impedance (block2272), the maximum average temperature during the treatment is evaluated (decision block2280). If this temperature is above a certain threshold (e.g., at or above 60° C.) then the high impedance may be attributed to high tissue temperature resulting in desiccation. In this event,message2274 may be displayed instructing the clinician to check for a constriction or protrusion (i.e., to image the treatment site) and to avoid treating again in the same location. Conversely, if the temperature is below the threshold (e.g., below 60° C.), thealgorithm2270 proceeds todecision block2282.
• In the depicted embodiment, atdecision block2282, thealgorithm2270 evaluates if the high impedance event occurred early in treatment (e.g., in the first 20 seconds of energy delivery) when power is relatively low. If yes, it is unlikely that tissue temperature was high and more likely that the electrode initially had poor or no contact and subsequently established better contact, causing impedance to jump. In thisevent message2276 may be displayed instructing the clinician to attempt to establish better contact and repeat treatment at the same site. However, if the event occurs later in treatment (e.g., more than 20 seconds elapsed), thealgorithm2270 proceeds todecision block2284.
• Atdecision block2284, thealgorithm2270 evaluates when the high impedance event occurred during treatment. For example, if the event occurred after a predetermined period of time (e.g., 45 seconds), when the power has reached high levels, the algorithm proceeds to decision block2286. However, if the event occurred when power is being ramped up and is not at its highest (e.g., between 20 seconds and 45 seconds), the algorithm proceeds todecision block2288.
• At decision block2286, thealgorithm2270 calculates the percentage change in impedance (% ΔZ) at the time of the high impedance event compared to the impedance at a specified time (e.g., 45 seconds). This is the period when power is sustained at a high level. In one embodiment, the percentage change in impedance is calculated as:
• $\begin{array}{cc}\%\Delta Z=100*\frac{\left[\left(\mathrm{final}\mathrm{avg}Z\right)-\left(\mathrm{avg}Z@45\sec \right)\right]}{\left(\mathrm{avg}Z@45\sec \right)}& \left(2\right)\end{array}$
• If % ΔZ is greater than or equal to a predetermined amount (e.g., 7%) then it may be likely that tissue began to desiccate due to high temperature. In this event,message2274 may be displayed instructing the clinician to check for a constriction or protrusion (i.e., to image the treatment site) and to avoid treating again in the same location. Otherwise, tissue desiccation is less likely and it is more likely that the electrode moved to cause the high impedance event. In this event,message2278 may be displayed notifying the clinician that the electrode may have moved. In the event the electrode has moved or may have moved, it is unlikely that tissue temperature reached a high level. Accordingly, it is expected that treating in the same location can be done if there are no or limited other locations to perform another treatment.
• Atdecision block2288, thealgorithm2270 may determine whether a sudden instability occurred. If such instability was present, it is likely that the electrode moved. In this event,message2278 may be displayed notifying the clinician that the electrode may have moved. As discussed above, the clinician may exhibit caution and avoid treating the original location or the location to which the electrode moved or the clinician may opt to treat in the same location if no other sites or a limited number of sites are available for further treatment. Otherwise, if no sudden instability occurred, it is more likely that the electrode had poor contact. In this event,message2276 may be displayed instructing the clinician to attempt to establish better contact and that treating the same site is safe.
• The same objective of detecting high impedance conditions can be achieved using alternate measurements and calculations. For example, in a further embodiment of thealgorithm2270, temperature and impedance data is taken for a sample time interval (e.g., 20 seconds). At a shorter time interval (e.g., every 1.5 seconds), the standard deviation of the impedance and temperature data is calculated. A first standard temperature for an interval is calculated as the standard deviation of the temperature divided by the standard deviation of the temperature at the initial time interval. If the standard deviation of the impedance measurements is greater than or equal to a pre-determined value (e.g., 10 Ohms), and the first standard temperature is greater than a pre-determined threshold (e.g., 3), then thealgorithm2270 can displaymessage2276, indicating poor electrode contact. However, if the standard deviation of the impedance measurement is outside the acceptable range, but the first standard temperature is within the acceptable range, thenmessage2278 will be displayed to alert the clinician that there is electrode instability.
• In accordance with a further embodiment of thealgorithm2270, the impedance of two or more electrodes24 (e.g., positioned on thetreatment region22 of thecatheter12 ofFIG. 1) can each provide an independent impedance reading. During delivery of thetherapeutic assembly22 to the treatment site (e.g., within the renal artery), the impedance readings of theelectrodes24 are typically different due to the anatomy of the vasculature, as thecatheter12 will conform to the path of least resistance, often bending at vasculature curves to only contact one wall of the renal artery. In some embodiments, once thetherapeutic assembly22 is in position for treatment, thetherapeutic assembly22 can be expanded circumferentially to contact the entire circumferential surface of a segment of the renal artery wall. This expansion can placemultiple electrodes24 in contact with the renal artery wall. As thetherapeutic assembly22 is expanded into the treatment configuration and theelectrodes24 make increased contact with the renal artery wall, the impedance values of theindividual electrodes24 can increase and/or approach the same value. With good, stable contact, fluctuations of impedance values also reduce as described above. Theenergy generator26 can continually or continuously monitor the individual impedance values. The values can then be compared to determine when contact has been effectively made, as an indication of successful treatment. In further embodiments, a moving average of impedance can be compared to a pre-determined range of variability of impedance values with limits set to guide stability measures.
• F. Feedback Related to Vasoconstriction
• In further embodiments, thesystem10 may generate a message related to the occurrence of vasoconstriction. In particular, while treatment is being delivered, blood vessels may contract to a less-than-optimal diameter. Constricted blood vessels can lead to reduced blood flow, increased treatment site temperatures, and increased blood pressure. Vasoconstriction can be measured by sampling the amplitude (the “envelope”) of real-time temperature data. The current envelope can be compared to a previous envelope sample taken (e.g., 200 ms prior). If the difference between the current envelope and the previous time point envelope is less than a pre-determined value (e.g., less than −0.5° C., or, in other words, there is a less than a 0.5 degree reduction in the present envelope value compared to the envelope value at the previous time point), then measurements are taken at a future time point (e.g., in 5 seconds). If the difference in average temperature at the future time point and the current time point is more than a given temperature threshold (e.g., more than 1° C.), then analgorithm2500 may determine that an undesirably high level of constriction exists, and can cease/alter energy delivery. In such an event, thesystem10 may generate a message indicating the high constriction condition. However, depending on the circumstances, different actions by the clinician may be appropriate.
• FIG. 25, for example, is a block diagram illustrating analgorithm2500 for providing operator feedback when a high degree of vessel constriction is detected in accordance with an embodiment of the present technology. In one implementation, thealgorithm2500 is executed in response to a high constriction level (e.g., vessels constricted at or below a certain diameter) (Block2502) and evaluates (decision block2504) data from the treatment to determine if the high constriction level involved a situation that included sudden instability or if it did not. An indication of sudden instability can indicate that theelectrode24 moved.
• In the event that sudden instability is not detected atdecision block2504, a first message may be displayed (block2506), such as an indication that a high constriction level has been detected and an instruction to a clinician to reduce treatment power. In further embodiments, the energy level may be automatically altered in response to the detected constriction level. In the event that sudden instability is detected atdecision block2504, an alternative message may be displayed (block2508) that, in addition to indicating the occurrence of the high constriction level and instructions to the clinician, may also indicate the possibility that theelectrode24 may have moved from its original site. Such feedback may prompt the clinician to alter or cease treatment.
• G. Feedback Related to Cardiac Factors
• 1. Feedback Related to Abnormal Heart Rate
• Like other physiological conditions mentioned above, in certain circumstances thesystem10 may generate a message related to the occurrence of an abnormal heart rate. In particular, while treatment is being delivered, heart rate may exceed or fall below desirable conditions (e.g., temporary procedural or chronic bradycardia). Instantaneous heart rate can be determined by measuring real-time temperature and impedance. More specifically, a real-time temperature reading can be filtered, for example, between 0.5 Hz and 2.5 Hz using a second order Butterworth filter. Local maxima of the filtered signal are determined. The local maxima are the detected peaks of the real-temperature signal. The instantaneous beat rate is the interval between the peaks, as the signal peaks correspond to the periodic change in the cardiac cycle.
• In one implementation, thesystem10 may cease/alter energy delivery if the heart rate falls outside a desirable range. In such an event, the system may generate a message indicating the adverse heart rate condition. However, depending on the circumstances, different actions by the clinician may be appropriate.
• FIG. 26A, for example, is a block diagram illustrating analgorithm2600 for providing operator feedback/instructions upon detection of an abnormal heart rate condition in accordance with an embodiment of the present technology. In one implementation, for example, thealgorithm2600 may be executed in response to an abnormal heart rate condition (e.g., above or below a pre-determined threshold) (Block2602). Atdecision block2604, thealgorithm2600 evaluates data from the treatment to determine if the detected abnormal heart rate condition involved a situation that included sudden instability. An indication of sudden instability can indicate that the electrode moved.
• In the event that sudden instability is not detected atdecision block2604, a first message may be displayed to the clinician (block2606), such as an indication that an abnormal heart rate has been detected and an instruction to the clinician to reduce treatment power. In further embodiments, the energy level may be automatically altered in response to the detected adverse heart rate. In the event that sudden instability is detected atdecision block2604, an alternative message may be displayed (block2608) that, in addition to indicating the occurrence of the abnormal heart rate and instructions to the clinician, may also indicate the possibility that the electrode may have moved from its original site. Such feedback may prompt the clinician to alter or cease treatment.
• 2. Feedback Related to Low Blood Flow
• Thesystem10 may also be configured to generate a message related to low blood flow conditions. For example, if blood flow falls below a certain level during treatment (or if vessels are undesirably narrow), the convective heat removed from theelectrode24 and tissue surface is reduced. Excessively high tissue temperatures can lead to the negative outcomes described above, such as thrombosis, charring, unreliable lesion size, etc. Reducing power from thegenerator26 to prevent the tissue from reaching an unacceptable temperature can lead to insufficient lesion depth, and nerves may not be heated to sufficient ablation temperatures. An algorithm can be used to measure blood flow or the loss of heat to the blood stream. In one embodiment, blood flow can be measured with a flow meter or a Doppler sensor placed in the renal artery on a separate catheter or on thetreatment catheter12. In another embodiment, heat loss or thermal decay can be measured by delivering energy (e.g., RF energy) to raise a blood, tissue, or substrate temperature. The energy can be turned off and the algorithm can include monitoring the temperature as a gauge of thermal decay. A rapid thermal decay may represent sufficient blood flow, while a gradual thermal decay may represent low blood flow. For example, in one embodiment, thealgorithm2610 can indicate a low blood flow if the slope of real-time temperature measurements over the starting temperature exceeds a preset threshold (e.g., 2.75) and the average temperature is greater than a preset temperature (e.g., 65° C.). In further embodiments, thermal decay and/or blood flow can be characterized by measuring temperature oscillations of an electrode delivering RF or resistive heat. At a given temperature or power delivery amplitude/magnitude, a narrow oscillation range may indicate a relatively low thermal decay/blood flow.
• FIG. 26B, for example, is a block diagram illustrating analgorithm2610 for providing operator feedback/instructions upon occurrence of a low blood flow condition in accordance with an embodiment of the present technology. In one implementation, thealgorithm2610 is executed in response to a detected low blood flow condition (e.g., flow below a pre-determined threshold) (Block2612). Atblock2614, thealgorithm2610 evaluates data from the treatment to determine if the low blood flow condition involved a situation that included sudden instability. In the event that sudden instability is not detected atdecision block2614, a first message may be displayed (block2616), such as an indication that low blood flow has been detected and an instruction to a clinician to reduce treatment power. In the event that sudden instability is detected, an alternative message may be displayed (block2618) that, in addition to indicating the occurrence of low blood flow and instructions to the clinician, may also indicate the possibility that the electrode may have moved from its original site. As noted above, such feedback may prompt the clinician to alter or cease treatment.
• In further embodiments, if blood flow or thermal decay values are lower than a typical or pre-determined threshold, theenergy delivery algorithm2610 can include automatically altering one or more conditions or characteristics of treatment or of the catheter to improve blood flow. For example, in one embodiment, thealgorithm2610 can respond to a low blood flow by pulsing the energy provided to the energy delivery element264 rather than providing continuous energy. This may allow the lower blood flow to more adequately remove heat from the tissue surface while still creating a sufficiently deep lesion to ablate a nerve.
• In another embodiment, thealgorithm2610 can include responding to a low blood flow by cooling the electrodes, as described in further detail in International Patent Application No. PCT/US2011/033491, filed Apr. 26, 2011, and U.S. patent application Ser. No. 12/874,457, filed Aug. 30, 2010. The foregoing applications are incorporated herein by reference in their entireties.
• In a further embodiment, thealgorithm2610 can respond to a low blood flow by requiring a manual increase of blood flow to the region. For example, a non-occlusive balloon can be inflated in the abdominal aorta, thereby increasing pressure and flow in the renal artery. The balloon can be incorporated on the treatment catheter or on a separate catheter.
• H. Feedback Display
• FIGS. 27A and 27B are screen shots illustrating representative generator display screens configured in accordance with aspects of the present technology.FIG. 27A, for example, is adisplay screen2700 for enhanced impedance tracking during treatment. Thedisplay2700 includes agraphical display2710 that tracks impedance measurements in real time over a selected period of time (e.g., 100 seconds). Thisgraphical display2710, for example, can be a dynamic, rolling display that is updated at periodic intervals to provide an operator with both instantaneous and historical tracking of impedance measurements. Thedisplay2710 can also includes animpedance display2720 with the current impedance as well as astandard deviation indication2722 for the impedance. In one embodiment, thestandard deviation indication2722 is configured to flash when this value is greater than 10. Such an indication can alert the operator of a contrast injection that is affecting the measurement or that the electrode may be unstable. Further information about contrast injection indications are described below.
• FIG. 27B, for example, is anotherrepresentative display screen2730 with additional information for an operator. In this example, thedisplay screen2730 is configured to alert the operator of a contrast injection and that the system is waiting for contrast to clear before commencing (e.g., disable RF for approximately 1 to 2 seconds until contrast clears). In another embodiment, thedisplay screen2730 may be configured to provide other alert messages (e.g., “POSSIBLE UNSTABLE ELECTRODE,” etc.). The additional information provided in thedisplay screens2710 and2730 described above is expected to improve contact assessment prior to RF ON, and improve treatment efficiency and efficacy.
• The additional information described above with reference toFIGS. 27A and 10B can be generated based on the algorithms described herein, or other suitable algorithms. In one embodiment, for example, an algorithm can continuously check for contrast injection/stability during pre-RF ON. If the electrode is stable and there is no contrast for ≧1 second, the baseline impedance Z is set equal to the average impedance Z over 1 second. In one particular example, the real time impedance is compared with two standard deviations of the mean impedance value within a one second window. In another specific example, the real time impedance may be compared with a fixed number (e.g., determine if the standard deviation is greater than 10). In still other examples, other arrangements may be used.
• If the real time impedance measurement is within this range, no message is displayed. However, if the real time impedance is not within two standard deviations of the mean, the electrode may not stable (i.e., drifting, moving, etc.) and one or both of the message(s) described above with reference toFIGS. 27A and 27B may be displayed to the user (e.g., “WAITING FOR CONTRAST TO CLEAR,” “POSSIBLE UNSTABLE ELECTRODE”). By way of example, for contrast injection detection, in addition to the standard deviation of the impedance, the algorithm may be configured to factor in the standard deviation of a real time temperature measurement to look for excursions of the real time temperature below a starting body temperature. The exact value for the temperature excursion cut off can vary. In one particular example, the system is configured such that if there is an increase in impedance (e.g., standard deviation >10) accompanied by a drop in real time temperature, the system will flag a Contrast Detected event leading to the “WAITING FOR CONTRAST TO CLEAR” message to be displayed to the operator. In other examples, however, other algorithms and/or ranges may be used to determine contrast injection events and/or the stability of the electrode. Further, in some embodiments the system may modify/adjust various treatment parameters based on detected conditions without displaying such messages to the clinician.
VII. PREPACKAGED KIT FOR DISTRIBUTION, TRANSPORT AND SALE OF THE DISCLOSED APPARATUSES AND SYSTEMS
• As shown inFIG. 28, one or more components of thesystem10 shown inFIG. 1 may be packaged together in akit276 for convenient delivery to and use by the customer/clinical operator. Components suitable for packaging include, thetreatment device12, thecable28 for connecting thetreatment device12 to theenergy generator26, the neutral ordispersive electrode38, and one or more guide catheters (e.g., a renal guide catheter).Cable28 may also be integrated into thetreatment device12 such that both components are packaged together. Each component may have its own sterile packaging (for components requiring sterilization) or the components may have dedicated sterilized compartments within the kit packaging. This kit may also include step-by-step instructions280 for use that provide the operator with technical product features and operating instructions for using thesystem10 andtreatment device12, including all methods of insertion, delivery, placement, and use of thetreatment device12 disclosed herein.
VIII. ADDITIONAL CLINICAL USES OF THE DISCLOSED TECHNOLOGY
• Although certain embodiments of the present techniques relate to at least partially denervating a kidney of a patient to block afferent and/or efferent neural communication from within a renal blood vessel (e.g., renal artery), the apparatuses, methods and systems described herein may also be used for other intravascular treatments. For example, the aforementioned catheter system, or select aspects of such system, may be placed in other peripheral blood vessels to deliver energy and/or electric fields to achieve a neuromodulatory affect by altering nerves proximate to these other peripheral blood vessels. There are a number of arterial vessels arising from the aorta which travel alongside a rich collection of nerves to target organs. Utilizing the arteries to access and modulate these nerves may have clear therapeutic potential in a number of disease states. Some examples include the nerves encircling the celiac trunk, superior mesenteric artery, and inferior mesenteric artery.
• Sympathetic nerves proximate to or encircling the arterial blood vessel known as the celiac trunk may pass through the celiac ganglion and follow branches of the celiac trunk to innervate the stomach, small intestine, abdominal blood vessels, liver, bile ducts, gallbladder, pancreas, adrenal glands, and kidneys. Modulating these nerves in whole (or in part via selective modulation) may enable treatment of conditions including, but not limited to, diabetes, pancreatitis, obesity, hypertension, obesity related hypertension, hepatitis, hepatorenal syndrome, gastric ulcers, gastric motility disorders, irritable bowel syndrome, and autoimmune disorders such as Crohn's disease.
• Sympathetic nerves proximate to or encircling the arterial blood vessel known as the inferior mesenteric artery may pass through the inferior mesenteric ganglion and follow branches of the inferior mesenteric artery to innervate the colon, rectum, bladder, sex organs, and external genitalia. Modulating these nerves in whole (or in part via selective modulation) may enable treatment of conditions including, but not limited to, GI motility disorders, colitis, urinary retention, hyperactive bladder, incontinence, infertility, polycystic ovarian syndrome, premature ejaculation, erectile dysfunction, dyspareunia, and vaginismus.
• While arterial access and treatments received have been provided herein, the disclosed apparatuses, methods and systems may also be used to deliver treatment from within a peripheral vein or lymphatic vessel.
IX. ADDITIONAL DISCUSSION OF PERTINENT ANATOMY AND PHYSIOLOGY
• The following discussion provides further details regarding pertinent patient anatomy and physiology. This section is intended to supplement and expand upon the previous discussion regarding the relevant anatomy and physiology, and to provide additional context regarding the disclosed technology and the therapeutic benefits associated with renal denervation. For example, as mentioned previously, several properties of the renal vasculature may inform the design of treatment devices and associated methods for achieving renal neuromodulation via intravascular access, and impose specific design requirements for such devices. Specific design requirements may include accessing the renal artery, facilitating stable contact between the energy delivery elements of such devices and a luminal surface or wall of the renal artery, and/or effectively modulating the renal nerves with the neuromodulatory apparatus.
• A. The Sympathetic Nervous System
• The Sympathetic Nervous System (SNS) is a branch of the autonomic nervous system along with the enteric nervous system and parasympathetic nervous system. It is always active at a basal level (called sympathetic tone) and becomes more active during times of stress. Like other parts of the nervous system, the sympathetic nervous system operates through a series of interconnected neurons. Sympathetic neurons are frequently considered part of the peripheral nervous system (PNS), although many lie within the central nervous system (CNS). Sympathetic neurons of the spinal cord (which is part of the CNS) communicate with peripheral sympathetic neurons via a series of sympathetic ganglia. Within the ganglia, spinal cord sympathetic neurons join peripheral sympathetic neurons through synapses. Spinal cord sympathetic neurons are therefore called presynaptic (or preganglionic) neurons, while peripheral sympathetic neurons are called postsynaptic (or postganglionic) neurons.
• At synapses within the sympathetic ganglia, preganglionic sympathetic neurons release acetylcholine, a chemical messenger that binds and activates nicotinic acetylcholine receptors on postganglionic neurons. In response to this stimulus, postganglionic neurons principally release noradrenaline (norepinephrine). Prolonged activation may elicit the release of adrenaline from the adrenal medulla.
• Once released, norepinephrine and epinephrine bind adrenergic receptors on peripheral tissues. Binding to adrenergic receptors causes a neuronal and hormonal response. The physiologic manifestations include pupil dilation, increased heart rate, occasional vomiting, and increased blood pressure. Increased sweating is also seen due to binding of cholinergic receptors of the sweat glands.
• The sympathetic nervous system is responsible for up- and down-regulating many homeostatic mechanisms in living organisms. Fibers from the SNS innervate tissues in almost every organ system, providing at least some regulatory function to things as diverse as pupil diameter, gut motility, and urinary output. This response is also known as sympatho-adrenal response of the body, as the preganglionic sympathetic fibers that end in the adrenal medulla (but also all other sympathetic fibers) secrete acetylcholine, which activates the secretion of adrenaline (epinephrine) and to a lesser extent noradrenaline (norepinephrine). Therefore, this response that acts primarily on the cardiovascular system is mediated directly via impulses transmitted through the sympathetic nervous system and indirectly via catecholamines secreted from the adrenal medulla.
• Science typically looks at the SNS as an automatic regulation system, that is, one that operates without the intervention of conscious thought. Some evolutionary theorists suggest that the sympathetic nervous system operated in early organisms to maintain survival as the sympathetic nervous system is responsible for priming the body for action. One example of this priming is in the moments before waking, in which sympathetic outflow spontaneously increases in preparation for action.
• 1. The Sympathetic Chain
• As shown inFIG. 29, the SNS provides a network of nerves that allows the brain to communicate with the body. Sympathetic nerves originate inside the vertebral column, toward the middle of the spinal cord in the intermediolateral cell column (or lateral horn), beginning at the first thoracic segment of the spinal cord and are thought to extend to the second or third lumbar segments. Because its cells begin in the thoracic and lumbar regions of the spinal cord, the SNS is said to have a thoracolumbar outflow. Axons of these nerves leave the spinal cord through the anterior rootlet/root. They pass near the spinal (sensory) ganglion, where they enter the anterior rami of the spinal nerves. However, unlike somatic innervation, they quickly separate out through white rami connectors which connect to either the paravertebral (which lie near the vertebral column) or prevertebral (which lie near the aortic bifurcation) ganglia extending alongside the spinal column.
• In order to reach the target organs and glands, the axons should travel long distances in the body, and, to accomplish this, many axons relay their message to a second cell through synaptic transmission. The ends of the axons link across a space, the synapse, to the dendrites of the second cell. The first cell (the presynaptic cell) sends a neurotransmitter across the synaptic cleft where it activates the second cell (the postsynaptic cell). The message is then carried to the final destination.
• In the SNS and other components of the peripheral nervous system, these synapses are made at sites called ganglia. The cell that sends its fiber is called a preganglionic cell, while the cell whose fiber leaves the ganglion is called a postganglionic cell. As mentioned previously, the preganglionic cells of the SNS are located between the first thoracic (T1) segment and third lumbar (L3) segments of the spinal cord. Postganglionic cells have their cell bodies in the ganglia and send their axons to target organs or glands.
• The ganglia include not just the sympathetic trunks but also the cervical ganglia (superior, middle and inferior), which sends sympathetic nerve fibers to the head and thorax organs, and the celiac and mesenteric ganglia (which send sympathetic fibers to the gut).
• 2. Innervation of the Kidneys
• AsFIG. 30 shows, the kidney is innervated by the renal plexus RP, which is intimately associated with the renal artery. The renal plexus RP is an autonomic plexus that surrounds the renal artery and is embedded within the adventitia of the renal artery. The renal plexus RP extends along the renal artery until it arrives at the substance of the kidney. Fibers contributing to the renal plexus RP arise from the celiac ganglion, the superior mesenteric ganglion, the aorticorenal ganglion and the aortic plexus. The renal plexus RP, also referred to as the renal nerve, is predominantly comprised of sympathetic components. There is no (or at least very minimal) parasympathetic innervation of the kidney.
• Preganglionic neuronal cell bodies are located in the intermediolateral cell column of the spinal cord. Preganglionic axons pass through the paravertebral ganglia (they do not synapse) to become the lesser splanchnic nerve, the least splanchnic nerve, first lumbar splanchnic nerve, second lumbar splanchnic nerve, and travel to the celiac ganglion, the superior mesenteric ganglion, and the aorticorenal ganglion. Postganglionic neuronal cell bodies exit the celiac ganglion, the superior mesenteric ganglion, and the aorticorenal ganglion to the renal plexus RP and are distributed to the renal vasculature.
• 3. Renal Sympathetic Neural Activity
• Messages travel through the SNS in a bidirectional flow. Efferent messages may trigger changes in different parts of the body simultaneously. For example, the sympathetic nervous system may accelerate heart rate; widen bronchial passages; decrease motility (movement) of the large intestine; constrict blood vessels; increase peristalsis in the esophagus; cause pupil dilation, piloerection (goose bumps) and perspiration (sweating); and raise blood pressure. Afferent messages carry signals from various organs and sensory receptors in the body to other organs and, particularly, the brain.
• Hypertension, heart failure and chronic kidney disease are a few of many disease states that result from chronic activation of the SNS, especially the renal sympathetic nervous system. Chronic activation of the SNS is a maladaptive response that drives the progression of these disease states. Pharmaceutical management of the renin-angiotensin-aldosterone system (RAAS) has been a longstanding, but somewhat ineffective, approach for reducing over-activity of the SNS.
• As mentioned above, the renal sympathetic nervous system has been identified as a major contributor to the complex pathophysiology of hypertension, states of volume overload (such as heart failure), and progressive renal disease, both experimentally and in humans. Studies employing radiotracer dilution methodology to measure overflow of norepinephrine from the kidneys to plasma revealed increased renal norepinephrine (NE) spillover rates in patients with essential hypertension, particularly so in young hypertensive subjects, which in concert with increased NE spillover from the heart, is consistent with the hemodynamic profile typically seen in early hypertension and characterized by an increased heart rate, cardiac output, and renovascular resistance. It is now known that essential hypertension is commonly neurogenic, often accompanied by pronounced sympathetic nervous system overactivity.
• Activation of cardiorenal sympathetic nerve activity is even more pronounced in heart failure, as demonstrated by an exaggerated increase of NE overflow from the heart and the kidneys to plasma in this patient group. In line with this notion is the recent demonstration of a strong negative predictive value of renal sympathetic activation on all-cause mortality and heart transplantation in patients with congestive heart failure, which is independent of overall sympathetic activity, glomerular filtration rate, and left ventricular ejection fraction. These findings support the notion that treatment regimens that are designed to reduce renal sympathetic stimulation have the potential to improve survival in patients with heart failure.
• Both chronic and end stage renal disease are characterized by heightened sympathetic nervous activation. In patients with end stage renal disease, plasma levels of norepinephrine above the median have been demonstrated to be predictive for both all-cause death and death from cardiovascular disease. This is also true for patients suffering from diabetic or contrast nephropathy. There is compelling evidence suggesting that sensory afferent signals originating from the diseased kidneys are major contributors to initiating and sustaining elevated central sympathetic outflow in this patient group; this facilitates the occurrence of the well known adverse consequences of chronic sympathetic over activity, such as hypertension, left ventricular hypertrophy, ventricular arrhythmias, sudden cardiac death, insulin resistance, diabetes, and metabolic syndrome.
• (i) Renal Sympathetic Efferent Activity
• Sympathetic nerves to the kidneys terminate in the blood vessels, the juxtaglomerular apparatus and the renal tubules. Stimulation of the renal sympathetic nerves causes increased renin release, increased sodium (Na+) reabsorption, and a reduction of renal blood flow. These components of the neural regulation of renal function are considerably stimulated in disease states characterized by heightened sympathetic tone and clearly contribute to the rise in blood pressure in hypertensive patients. The reduction of renal blood flow and glomerular filtration rate as a result of renal sympathetic efferent stimulation is likely a cornerstone of the loss of renal function in cardio-renal syndrome, which is renal dysfunction as a progressive complication of chronic heart failure, with a clinical course that typically fluctuates with the patient's clinical status and treatment. Pharmacologic strategies to thwart the consequences of renal efferent sympathetic stimulation include centrally acting sympatholytic drugs, beta blockers (intended to reduce renin release), angiotensin converting enzyme inhibitors and receptor blockers (intended to block the action of angiotensin II and aldosterone activation consequent to renin release) and diuretics (intended to counter the renal sympathetic mediated sodium and water retention). However, the current pharmacologic strategies have significant limitations including limited efficacy, compliance issues, side effects and others.
• (ii) Renal Sensory Afferent Nerve Activity
• The kidneys communicate with integral structures in the central nervous system via renal sensory afferent nerves. Several forms of “renal injury” may induce activation of sensory afferent signals. For example, renal ischemia, reduction in stroke volume or renal blood flow, or an abundance of adenosine enzyme may trigger activation of afferent neural communication. As shown inFIGS. 31A and 31B, this afferent communication might be from the kidney to the brain or might be from one kidney to the other kidney (via the central nervous system). These afferent signals are centrally integrated and may result in increased sympathetic outflow. This sympathetic drive is directed towards the kidneys, thereby activating the RAAS and inducing increased renin secretion, sodium retention, volume retention and vasoconstriction. Central sympathetic over activity also impacts other organs and bodily structures innervated by sympathetic nerves such as the heart and the peripheral vasculature, resulting in the described adverse effects of sympathetic activation, several aspects of which also contribute to the rise in blood pressure.
• The physiology therefore suggests that (i) modulation of tissue with efferent sympathetic nerves will reduce inappropriate renin release, salt retention, and reduction of renal blood flow, and that (ii) modulation of tissue with afferent sensory nerves will reduce the systemic contribution to hypertension and other disease states associated with increased central sympathetic tone through its direct effect on the posterior hypothalamus as well as the contralateral kidney. In addition to the central hypotensive effects of afferent renal denervation, a desirable reduction of central sympathetic outflow to various other sympathetically innervated organs such as the heart and the vasculature is anticipated.
• B. Additional Clinical Benefits of Renal Denervation
• As provided above, renal denervation is likely to be valuable in the treatment of several clinical conditions characterized by increased overall and particularly renal sympathetic activity such as hypertension, metabolic syndrome, insulin resistance, diabetes, left ventricular hypertrophy, chronic end stage renal disease, inappropriate fluid retention in heart failure, cardio-renal syndrome, and sudden death. Since the reduction of afferent neural signals contributes to the systemic reduction of sympathetic tone/drive, renal denervation might also be useful in treating other conditions associated with systemic sympathetic hyperactivity. Accordingly, renal denervation may also benefit other organs and bodily structures innervated by sympathetic nerves, including those identified inFIG. 29. For example, as previously discussed, a reduction in central sympathetic drive may reduce the insulin resistance that afflicts people with metabolic syndrome and Type II diabetics. Additionally, patients with osteoporosis are also sympathetically activated and might also benefit from the down regulation of sympathetic drive that accompanies renal denervation.
• C. Achieving Intravascular Access to the Renal Artery
• In accordance with the present technology, neuromodulation of a left and/or right renal plexus RP, which is intimately associated with a left and/or right renal artery, may be achieved through intravascular access. AsFIG. 32A shows, blood moved by contractions of the heart is conveyed from the left ventricle of the heart by the aorta. The aorta descends through the thorax and branches into the left and right renal arteries. Below the renal arteries, the aorta bifurcates at the left and right iliac arteries. The left and right iliac arteries descend, respectively, through the left and right legs and join the left and right femoral arteries.
• AsFIG. 32B shows, the blood collects in veins and returns to the heart, through the femoral veins into the iliac veins and into the inferior vena cava. The inferior vena cava branches into the left and right renal veins. Above the renal veins, the inferior vena cava ascends to convey blood into the right atrium of the heart. From the right atrium, the blood is pumped through the right ventricle into the lungs, where it is oxygenated. From the lungs, the oxygenated blood is conveyed into the left atrium. From the left atrium, the oxygenated blood is conveyed by the left ventricle back to the aorta.
• As will be described in greater detail later, the femoral artery may be accessed and cannulated at the base of the femoral triangle just inferior to the midpoint of the inguinal ligament. A catheter may be inserted percutaneously into the femoral artery through this access site, passed through the iliac artery and aorta, and placed into either the left or right renal artery. This comprises an intravascular path that offers minimally invasive access to a respective renal artery and/or other renal blood vessels.
• The wrist, upper arm, and shoulder region provide other locations for introduction of catheters into the arterial system. For example, catheterization of either the radial, brachial, or axillary artery may be utilized in select cases. Catheters introduced via these access points may be passed through the subclavian artery on the left side (or via the subclavian and brachiocephalic arteries on the right side), through the aortic arch, down the descending aorta and into the renal arteries using standard angiographic technique.
• D. Properties and Characteristics of the Renal Vasculature
• Since neuromodulation of a left and/or right renal plexus RP may be achieved in accordance with the present technology through intravascular access, properties and characteristics of the renal vasculature may impose constraints upon and/or inform the design of apparatus, systems, and methods for achieving such renal neuromodulation. Some of these properties and characteristics may vary across the patient population and/or within a specific patient across time, as well as in response to disease states, such as hypertension, chronic kidney disease, vascular disease, end-stage renal disease, insulin resistance, diabetes, metabolic syndrome, etc. These properties and characteristics, as explained herein, may have bearing on the efficacy of the procedure and the specific design of the intravascular device. Properties of interest may include, for example, material/mechanical, spatial, fluid dynamic/hemodynamic and/or thermodynamic properties.
• As discussed previously, a catheter may be advanced percutaneously into either the left or right renal artery via a minimally invasive intravascular path. However, minimally invasive renal arterial access may be challenging, for example, because as compared to some other arteries that are routinely accessed using catheters, the renal arteries are often extremely tortuous, may be of relatively small diameter, and/or may be of relatively short length. Furthermore, renal arterial atherosclerosis is common in many patients, particularly those with cardiovascular disease. Renal arterial anatomy also may vary significantly from patient to patient, which further complicates minimally invasive access. Significant inter-patient variation may be seen, for example, in relative tortuosity, diameter, length, and/or atherosclerotic plaque burden, as well as in the take-off angle at which a renal artery branches from the aorta. Apparatus, systems and methods for achieving renal neuromodulation via intravascular access should account for these and other aspects of renal arterial anatomy and its variation across the patient population when minimally invasively accessing a renal artery.
• In addition to complicating renal arterial access, specifics of the renal anatomy also complicate establishment of stable contact between neuromodulatory apparatus and a luminal surface or wall of a renal artery. When the neuromodulatory apparatus includes an energy delivery element, such as an electrode, consistent positioning and appropriate contact force applied by the energy delivery element to the vessel wall are important for predictability. However, navigation is impeded by the tight space within a renal artery, as well as tortuosity of the artery. Furthermore, establishing consistent contact is complicated by patient movement, respiration, and/or the cardiac cycle because these factors may cause significant movement of the renal artery relative to the aorta, and the cardiac cycle may transiently distend the renal artery (i.e., cause the wall of the artery to pulse.
• Even after accessing a renal artery and facilitating stable contact between neuromodulatory apparatus and a luminal surface of the artery, nerves in and around the adventia of the artery should be safely modulated via the neuromodulatory apparatus. Effectively applying thermal treatment from within a renal artery is non-trivial given the potential clinical complications associated with such treatment. For example, the intima and media of the renal artery are highly vulnerable to thermal injury. As discussed in greater detail below, the intima-media thickness separating the vessel lumen from its adventitia means that target renal nerves may be multiple millimeters distant from the luminal surface of the artery. Sufficient energy should be delivered to or heat removed from the target renal nerves to modulate the target renal nerves without excessively cooling or heating the vessel wall to the extent that the wall is frozen, desiccated, or otherwise potentially affected to an undesirable extent. A potential clinical complication associated with excessive heating is thrombus formation from coagulating blood flowing through the artery. Given that this thrombus may cause a kidney infarct, thereby causing irreversible damage to the kidney, thermal treatment from within the renal artery should be applied carefully. Accordingly, the complex fluid mechanics and thermodynamic conditions present in the renal artery during treatment, particularly those that may impact heat transfer dynamics at the treatment site, may be important in applying energy (e.g., heating thermal energy) and/or removing heat from the tissue (e.g., cooling thermal conditions) from within the renal artery.
• The neuromodulatory apparatus should also be configured to allow for adjustable positioning and repositioning of the energy delivery element within the renal artery since location of treatment may also impact clinical efficacy. For example, it may be tempting to apply a full circumferential treatment from within the renal artery given that the renal nerves may be spaced circumferentially around a renal artery. In some situations, full-circle lesion likely resulting from a continuous circumferential treatment may be potentially related to renal artery stenosis. Therefore, the formation of more complex lesions along a longitudinal dimension of the renal artery via the mesh structures described herein and/or repositioning of the neuromodulatory apparatus to multiple treatment locations may be desirable. It should be noted, however, that a benefit of creating a circumferential ablation may outweigh the potential of renal artery stenosis or the risk may be mitigated with certain embodiments or in certain patients and creating a circumferential ablation could be a goal. Additionally, variable positioning and repositioning of the neuromodulatory apparatus may prove to be useful in circumstances where the renal artery is particularly tortuous or where there are proximal branch vessels off the renal artery main vessel, making treatment in certain locations challenging. Manipulation of a device in a renal artery should also consider mechanical injury imposed by the device on the renal artery. Motion of a device in an artery, for example by inserting, manipulating, negotiating bends and so forth, may contribute to dissection, perforation, denuding intima, or disrupting the interior elastic lamina.
• Blood flow through a renal artery may be temporarily occluded for a short time with minimal or no complications. However, occlusion for a significant amount of time should be avoided because to prevent injury to the kidney such as ischemia. It could be beneficial to avoid occlusion all together or, if occlusion is beneficial to the embodiment, to limit the duration of occlusion, for example to 2-5 minutes.
• Based on the above described challenges of (1) renal artery intervention, (2) consistent and stable placement of the treatment element against the vessel wall, (3) effective application of treatment across the vessel wall, (4) positioning and potentially repositioning the treatment apparatus to allow for multiple treatment locations, and (5) avoiding or limiting duration of blood flow occlusion, various independent and dependent properties of the renal vasculature that may be of interest include, for example, (a) vessel diameter, vessel length, intima-media thickness, coefficient of friction, and tortuosity; (b) distensibility, stiffness and modulus of elasticity of the vessel wall; (c) peak systolic, end-diastolic blood flow velocity, as well as the mean systolic-diastolic peak blood flow velocity, and mean/max volumetric blood flow rate; (d) specific heat capacity of blood and/or of the vessel wall, thermal conductivity of blood and/or of the vessel wall, and/or thermal convectivity of blood flow past a vessel wall treatment site and/or radiative heat transfer; (e) renal artery motion relative to the aorta induced by respiration, patient movement, and/or blood flow pulsatility: and (f) as well as the take-off angle of a renal artery relative to the aorta. These properties will be discussed in greater detail with respect to the renal arteries. However, dependent on the apparatus, systems and methods utilized to achieve renal neuromodulation, such properties of the renal arteries, also may guide and/or constrain design characteristics.
• As noted above, an apparatus positioned within a renal artery should conform to the geometry of the artery. Renal artery vessel diameter, D_RA, typically is in a range of about 2-10 mm, with most of the patient population having a D_RAof about 4 mm to about 8 mm and an average of about 6 mm. Renal artery vessel length, L_RA, between its ostium at the aorta/renal artery juncture and its distal branchings, generally is in a range of about 5-70 mm, and a significant portion of the patient population is in a range of about 20-50 mm. Since the target renal plexus is embedded within the adventitia of the renal artery, the composite Intima-Media Thickness, IMT, (i.e., the radial outward distance from the artery's luminal surface to the adventitia containing target neural structures) also is notable and generally is in a range of about 0.5-2.5 mm, with an average of about 1.5 mm. Although a certain depth of treatment is important to reach the target neural fibers, the treatment should not be too deep (e.g., >5 mm from inner wall of the renal artery) to avoid non-target tissue and anatomical structures such as the renal vein.
• An additional property of the renal artery that may be of interest is the degree of renal motion relative to the aorta, induced by respiration and/or blood flow pulsatility. A patient's kidney, which located at the distal end of the renal artery, may move as much as 4″ cranially with respiratory excursion. This may impart significant motion to the renal artery connecting the aorta and the kidney, thereby requiring from the neuromodulatory apparatus a unique balance of stiffness and flexibility to maintain contact between the thermal treatment element and the vessel wall during cycles of respiration. Furthermore, the take-off angle between the renal artery and the aorta may vary significantly between patients, and also may vary dynamically within a patient, e.g., due to kidney motion. The take-off angle generally may be in a range of about 30°-135°.
X. CONCLUSION
• The above detailed descriptions of embodiments of the technology are not intended to be exhaustive or to limit the technology to the precise form disclosed above. Although specific embodiments of, and examples for, the technology are described above for illustrative purposes, various equivalent modifications are possible within the scope of the technology, as those skilled in the relevant art will recognize. For example, while steps are presented in a given order, alternative embodiments may perform steps in a different order. The various embodiments described herein may also be combined to provide further embodiments.
• From the foregoing, it will be appreciated that specific embodiments of the technology have been described herein for purposes of illustration, but well-known structures and functions have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments of the technology. Where the context permits, singular or plural terms may also include the plural or singular term, respectively.
• Moreover, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in reference to a list of two or more items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of the items in the list. Additionally, the term “comprising” is used throughout to mean including at least the recited feature(s) such that any greater number of the same feature and/or additional types of other features are not precluded. It will also be appreciated that specific embodiments have been described herein for purposes of illustration, but that various modifications may be made without deviating from the technology. Further, while advantages associated with certain embodiments of the technology have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the technology. Accordingly, the disclosure and associated technology can encompass other embodiments not expressly shown or described herein.

Claims (33)

1. A catheter apparatus, comprising:

an elongated, flexible tubular member extending along a longitudinal axis, wherein the elongated tubular member has a proximal portion, a distal portion, and a central lumen therein, and wherein the tubular member comprises—

a deflection region at the distal portion, wherein the deflection region includes a plurality of slots in a wall of the tubular member and substantially transverse to the longitudinal axis; and

an orientation region adjacent to the deflection region and between the deflection region and a distal end of the proximal portion of the elongated tubular member, wherein the orientation region includes a plurality of slots in the wall of the tubular member and substantially transverse to the longitudinal axis;

wherein the tubular member is selectively transformable between—

a first state in which the deflection region is generally straight extending along the longitudinal axis, and

a second state in which the deflection region comprises a generally helically-shaped structure and the orientation region has an elbow shape such that the distal end of the proximal portion of the tubular member is aimed through an interior of the helix;

a plurality of energy delivery elements carried by the deflection region and including at least a first energy delivery element and a second energy delivery element, wherein, when the tubular member is in the second state, the first and second energy delivery elements are axially and radially spaced from one another about the longitudinal axis; and

a control member operatively engaged with the tubular member to control movement of the flexible tubular member between the first state and the second state.

2. The catheter apparatus ofclaim 1 wherein, in the second state, the deflection region defines a helical axis generally parallel with the longitudinal axis and about which the helical structure revolves to define a plurality of revolutions and a helical diameter of the helical structure, and wherein the helical structure has a distal end and a proximal end spaced along the helical axis to define a helix length.

3. The catheter apparatus ofclaim 2 wherein the orientation region is configured to substantially axially align the helical axis with the longitudinal axis when the tubular member is in the second state, and wherein the slots of the orientation region are radially offset about the longitudinal axis from the slots of the deflection region.

4. The catheter apparatus ofclaim 1 wherein the helical shaped structure comprises at least two revolutions to define at least two contact points for engaging a wall of a peripheral blood vessel.

5. The catheter apparatus ofclaim 1 wherein:

the slots of the deflection region are elongated deflection slots generally parallel to each other along the tubular member, and wherein the deflection slots extend completely through the wall of the tubular member; and

the slots of the orientation region are elongated orientation slots generally parallel to each other along the tubular member, and wherein the orientation slots extend completely through the wall of the tubular member.

6. The catheter apparatus ofclaim 5 wherein:

center points of each of the orientation slots in the orientation region are spaced apart along a first progressive axis extending along the length of the tubular member; and

center points of each of the deflection slots in the deflection region are spaced apart along a second progressive axis extending along the length of the tubular member and radially offset about the longitudinal axis from the first progressive axis.

7. The catheter apparatus ofclaim 6 wherein, in the first state:

the first progressive axis is substantially parallel to the longitudinal axis; and

the second progressive axis defines an angle of about 0.5 degrees (0.5°) with respect to a line parallel to the longitudinal axis.

8. The catheter apparatus ofclaim 6 wherein, in the first state:

the first progressive axis is substantially parallel to the longitudinal axis; and

the second progressive axis defines an angle of about two degrees (2°) with respect to a line parallel to the longitudinal axis.

9. The catheter apparatus ofclaim 6 wherein, in the first state, the first progressive axis defines an angle of between about 45 degrees (45°) and 90 degrees (90°) with respect to a line parallel to the longitudinal axis.

10. The catheter apparatus ofclaim 1 wherein the plurality of slots in at least one of the deflection and orientation regions includes at least one opening elongated circumferentially about the longitudinal axis over an angle of about 300°.

11. The catheter apparatus ofclaim 10 wherein the at least one opening defines an arc length of about 0.04 inch (1.02 mm).

12. The catheter apparatus ofclaim 10 wherein the at least one opening includes a central region and two end regions disposed about and contiguous with the central region, and wherein the central region and the two end regions each define a width of the opening extending in the direction of the longitudinal axis, the width defined by the two end regions being greater than the width defined by the central region.

13. The catheter apparatus ofclaim 12 wherein each of the two end regions are substantially circular.

14. The catheter apparatus ofclaim 12 wherein each of the two end regions and the central region are substantially rectangular, and wherein the two end regions are elongated parallel to the longitudinal axis and the central region is elongated perpendicular to the longitudinal axis.

15. The catheter apparatus ofclaim 12 wherein each of the two end regions are substantially rectangular and elongated parallel to the longitudinal axis, and the central region defines a circular portion centered about the opening.

16. The catheter apparatus ofclaim 1 wherein the plurality of slots in the deflection region comprises 30 or fewer deflection slots, and wherein the individual deflection slots are spaced apart from one another by a distance from about 0.03 inch (0.76 mm) to about 0.04 inch (1.02 mm).

17. The catheter apparatus ofclaim 1 wherein the control member comprises a wire disposed in the central lumen, and wherein the wire has a first end portion coupled to the distal portion of the tubular member such that increasing a tension in the wire controls selectively transforms the deflection region of the tubular member between the first state and the second state.

18. The catheter apparatus ofclaim 17, further comprising a handle assembly at the proximal portion of the tubular member, and wherein a second end portion of the wire is operably coupled to the handle to apply the tension in the wire.

19. A catheter apparatus, comprising:

an elongated shaft having a proximal portion and a distal portion, wherein the distal portion of the shaft is configured for intravascular delivery to a renal artery of a human patient;

a control wire slidably disposed within the shaft and affixed at or near the distal portion of the shaft;

a therapeutic assembly at the distal portion of the elongated shaft, the therapeutic assembly including a plurality of energy delivery elements including at least a first energy delivery element and a second energy delivery element; and

wherein the therapeutic assembly is transformable, via the control wire, between—

a collapsed configuration wherein the therapeutic assembly defines a delivery profile of about 0.085 inch (2.16 mm) or less about a central axis, and

a expanded configuration wherein the first and the second energy delivery elements are axially and radially spaced from one another along and about the central axis, respectively.

20. The catheter apparatus ofclaim 19, further comprising a tip member at the distal portion of the elongated shaft, wherein the control wire is coupled to the tip member, and wherein the tip member is configured for atraumatic insertion in the renal artery.

21. The catheter apparatus ofclaim 19, further comprising a handle assembly at the proximal portion of the shaft and operably coupled to the control wire, wherein the handle assembly is configured to transition the therapeutic assembly between the collapsed and the expanded configurations.

22. The catheter apparatus ofclaim 19, wherein the distal region includes a plurality of slots formed in the distal portion of the elongated shaft, wherein the slots are generally parallel to each other and generally transverse to the central axis when the therapeutic assembly is in the collapsed configuration.

23. The catheter apparatus ofclaim 19 wherein the control wire comprises ultra high molecular weight polyethylene.

24. The catheter apparatus ofclaim 19 wherein the distal region comprises a slot, and wherein the control wire is anchored to the slot.

25. The catheter apparatus ofclaim 19, further comprising a coil at the distal region, and wherein the control wire is anchored to the coil.

26. The catheter apparatus ofclaim 19 wherein a distal end of the control wire is knotted and coated with a polymer material.

27. The catheter apparatus ofclaim 19 wherein:

the support structure is configured to vary between—

a substantially linear shaped structure in the collapsed configuration; and

a helical shaped structure in the expanded configuration defining a helical axis generally parallel with the central axis and about which the helical shaped structure revolves to define a plurality of revolutions and a helical diameter of the helical structure, and wherein the helical structure comprises a distal portion and a proximal portion spaced along the helical axis to define a helix length; and

the control wire is configured to operably engage the support structure to control movement of the support structure between the collapsed configuration and the expanded configuration.

28. The catheter apparatus ofclaim 27 wherein the control wire is substantially aligned along the helical axis and operably coupled to the distal end of the helical structure such that axial translation of the control wire along the helical axis controls movement of the support structure between the collapsed configuration and the expanded configuration.

29. The catheter apparatus ofclaim 28 wherein axial translation of the control wire in the distal direction reduces the radial distance of the first and second energy delivery elements from the central axis.

30. The catheter apparatus ofclaim 29 wherein axial translation of the control wire in the distal direction increases the helix length and reduces the helical diameter.

31. The catheter apparatus ofclaim 27 wherein the helical structure is configured to rotate with respect to the control wire.

32. The catheter apparatus ofclaim 27, further comprising a stop member disposed along the helical axis to limit axial translation of the control wire.

33. The catheter apparatus ofclaim 27 wherein the control wire comprises a central lumen, and wherein catheter apparatus further comprises a guide wire disposed in the central lumen of the control wire for locating the support structure at a target treatment location along the renal artery.

Images