US20090276022A1 - Techniques for placing medical leads for electrical stimulation of nerve tissue - Google Patents

Abstract

This disclosure is directed to extra, intra, and transvascular medical lead placement techniques for arranging medical leads and electrical stimulation and/or sensing electrodes proximate nerve tissue within a patient.

Description

• This application claims the benefit of U.S. Provisional Application Nos. 61/007,542, 61/007,543, 61/190,045, and 61/190,046, all of which were filed Apr. 30, 2008, and the entire contents of each of which is incorporated herein by this reference.
TECHNICAL FIELD
• The disclosure relates to medical devices and, more particularly, medical devices that deliver electrical stimulation therapy.
BACKGROUND
• A wide variety of implantable medical devices (“IMD”) that deliver therapy to or monitor a physiologic condition of a patient have been clinically implanted or proposed for clinical implantation in patients. Such devices may deliver therapy or monitor the heart, muscle, nerve, the brain, the stomach or other organs or tissues. In some cases, IMD's deliver electrical stimulation therapy and/or monitor physiological signals via one or more electrodes or sensor elements, at least some of which may be included as part of one or more elongated implantable medical leads. Implantable medical leads may be configured to allow electrodes or sensors to be positioned at desired locations for delivery of stimulation or sensing electrical activity or other physiological parameters. For example, electrodes or sensors may be located at a distal portion of the lead. A proximal portion of the lead is coupled to an IMD housing, which contains electronic circuitry such as stimulation generation and/or sensing circuitry. In some cases, electrodes or sensors are positioned on an IMD housing as an alternative or in addition to electrodes or sensors deployed on one or more leads.
• One example IMD is an electrical stimulation device directed to nerve tissue stimulation, which is sometimes referred to as an implantable nerve stimulator or implantable neurostimulator (“INS”). One particular application of nerve tissue stimulation is vagal nerve stimulation. Vagal nerve stimulation may provide therapeutic effects for heart failure, as well as other conditions including, e.g., depression, epilepsy and various digestion conditions. Some vagal nerve stimulators, as well as nerve trunk stimulators in general, have employed cuff electrodes to surround the nerve tissue and anchor the stimulator lead and/or electrodes within a patient. Cuff electrodes have some disadvantages, however, including, that such electrodes require relatively invasive techniques for placing them within a patient. In the case of vagal nerve stimulation, cuff electrodes require an incision in the neck and dissection of the vagus from within the carotid sheath for placement around the nerve. Additionally, cuff electrodes are known to cause lesions or otherwise damage the nerve tissue, which may lead to deleterious effects on nerve function, as well as the development of scar tissue.
SUMMARY
• In general, examples disclosed herein are directed to extra, intra, and transvascular medical lead placement techniques for arranging medical leads and electrical stimulation and/or sensing electrodes proximate nerve tissue within a patient.
• In one example, a system for implantation of a medical lead is configured to deliver electrical stimulation to nerve tissue located adjacent a blood vessel. The system includes a catheter adapted to be positioned within a lumen of the blood vessel adjacent the nerve tissue. A deployment member is extendable and retractable from the catheter through a wall of the blood vessel lumen. An electrode is connected to the deployment member such that the deployment member positions the electrode outside of the blood vessel proximate the nerve tissue when the deployment member is extended through the lumen wall.
• In another example, a method includes deploying a delivery catheter through a lumen of a blood vessel to a location proximate a target nerve tissue site outside the blood vessel. A location of the nerve tissue is identified with respect to the blood vessel with one or more sensors connected to the delivery catheter. An electrical stimulation electrode is advanced from the catheter through a wall of the blood vessel toward the nerve tissue.
• The details of one or more examples according to this disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.
BRIEF DESCRIPTION OF DRAWINGS
• FIG. 1A is a conceptual diagram illustrating an example therapy system including an implantable medical device (IMD) that delivers cardiac and nerve tissue stimulation to a patient.
• FIG. 1B is a conceptual diagram illustrating an example therapy system including an implantable cardiac device (ICD) and an implantable neurostimulator (INS).
• FIG. 2 is a functional block diagram of the IMD ofFIG. 1A.
• FIG. 3 is a functional block diagram of an example medical device programmer.
• FIGS. 4 and 5 are schematic illustrations depicting relevant human anatomy for lead placement techniques described herein.
• FIG. 6 is a schematic illustration depicting a medical lead placed extravascularly adjacent a vagus nerve.
• FIG. 7 is a flow chart illustrating an example extravascular lead placement method.
• FIGS. 8A and 8B show two example sleeve anchors for use with extravascular lead placement techniques according to this disclosure.
• FIG. 8C shows deployable lobe member for use with extravascular lead placement techniques according to this disclosure.
• FIG. 9 is a schematic illustration depicting a medical lead placed intravascularly within the internal jugular vein adjacent a vagus nerve.
• FIG. 10 is a flow chart illustrating an example intravascular lead placement method.
• FIG. 11 is a schematic illustration of a two dimensional ultrasonic image generated by a sensor used in conjunction with the intravascular lead placement arrangement shown inFIG. 9.
• FIGS. 12A and 12B show several example deployment members for use in intravascular lead placement methods and systems according to this disclosure.
• FIG. 13 is a schematic illustration depicting a medical lead placed intravascularly and actively fixed to a wall of the internal jugular vein adjacent a vagus nerve.
• FIGS. 14A-14J are elevation front views of example anchors that may be used alone or in combination to anchor or bias a medical lead and/or electrode placed in accordance with examples disclosed herein.
• FIG. 15 is a schematic illustration depicting a cylindrical lead member connected to a medical lead placed intravascularly within the internal jugular vein adjacent a vagus nerve.
• FIG. 16 is a flow chart illustrating an example method of intravascularly placing the cylindrical lead member ofFIG. 15.
• FIGS. 17A and 17B are schematic illustrations of a cylindrical lead member arranged within a delivery catheter.
• FIGS. 18A-18D are schematic illustrations of different examples of a cylindrical lead member that is expandable and contractible for deployment and redeployment within a blood vessel.
• FIG. 19 is a schematic illustration depicting a medical lead placed transvascularly through a wall of the internal jugular toward a vagus nerve.
• FIG. 20 is a flow chart illustrating an example transvascular lead placement method.
• FIGS. 21A-21D show several example deployment members for use in transvascular lead placement methods and systems according to this disclosure.
• FIG. 22 shows one example of a deployment member that employs a guide member constructed from a shape memory material.
• FIGS. 23A and 23B illustrate example arrangements of electrode pairs in flanking, non-contacting relationship with a vagus nerve.
DETAILED DESCRIPTION
• In general, this disclosure is directed toward techniques for placing medical leads proximate nerve tissue within a patient for electrical stimulation of the tissue without the use of potentially deleterious electrode configurations including e.g., cuff electrodes. Techniques disclosed herein are also generally directed to flexible placement techniques and structures that provide for one or more temporary lead placements and stimulation tests, prior to chronically placing the leads within the patient for nerve tissue stimulation. Furthermore, techniques according to this disclosure are adapted to enable minimally invasive introduction of the medical leads into the patient. Implantable electrical stimulation systems and methods in accordance with this disclosure may be used to deliver therapy to patients suffering from conditions that range from chronic pain, tremor, Parkinson's disease, and epilepsy, to urinary or fecal incontinence, sexual dysfunction, obesity, spasticity, and gastroparesis. Specific types of electrical stimulation therapies for treating such conditions include, e.g., cardiac pacing, neurostimulation, muscle stimulation, or the like.
• Systems disclosed generally include one or more medical leads adapted to be placed within a patient proximate nerve tissue targeted for electrical stimulation therapy. The leads include one or more electrodes that are arranged toward a distal end of the leads. In some examples, the leads are anchored at least proximate the distal end of the leads by or according to one or more structures or techniques described in detail below. The medical leads are connected to an electrical stimulator including a processor adapted to carry out the electrical stimulation of the target nerve tissue according to, e.g., one or more therapy programs stored in non-volatile memory. The electrical stimulator may include, generally, stimulation generation and/or sensing circuitry. In some examples, the stimulator may also include circuitry for cardiac rhythm therapy, e.g., one or more of pacing, cardioversion, and/or defibrillation therapy, to a heart of a patient. The stimulator may be located at a distance from the target tissue site and coupled to a proximal end of the leads. In another example, however, the electrical stimulator may include one or more electrodes or sensors on its housing or a member, element or structure coupled to the housing, may be placed in conjunction with the electrodes or sensors proximate the target nerve tissue site, and may be powered by, e.g., battery or a remote power source. In some examples, the electrical stimulator may be powered by radio frequency pulses delivered from either an external or a subcutaneously implanted RF transmitter to a receiver unit arranged with the stimulator, lead, and/or electrodes. In other examples, some part of the stimulator, lead, or electrodes may be composed of a piezoelectric material that can generate current when excited mechanically by ultra sound waves transmitted from an external or implanted source. In yet another example, two separate implantable devices, e.g. an INS and a cardiac therapy device are individually implanted and communicatively connected to one another. Placement of the leads and electrodes proximate the nerve tissue includes extravascular, intravascular, and transvascular placement structures and techniques.
• The techniques disclosed herein are described generally in the context of stimulation of one of the vagus nerves on the vagal nerve trunk in the neck of a human patient. Vagal nerve stimulation is useful in treating various conditions including, e.g., heart failure, depression, epilepsy, and various gastrointestinal conditions. However, the methods and systems disclosed are also applicable to stimulation and treatment of other nerve tissues that are located in diverse locations. For example, the disclosed techniques may be used in the stimulation of a hypoglossal nerve. In other examples, a nerve plexus that forms a node of intersecting nerves including, e.g., the cervical, brachial, lumbar, sacral, or solar plexus may be stimulated using methods and systems according to this disclosure. Additionally, the techniques may be used for stimulation of nerve ganglia including, e.g., one or more ganglia of a nerve plexus.
• As an additional example, the techniques disclosed herein may be used in the stimulation of vascular baroreceptors including, e.g., carotid baroreceptors. Baroreceptors are sensors located in blood vessels that detect the pressure of blood flowing therethrough, and can send messages to the central nervous system to increase or decrease total peripheral resistance and cardiac output. The receptors function by detecting the amount a blood vessel wall stretches, and sending a signal to the nervous system in response to the detected expansion of the vessel. Baroreceptors act as part of a negative feedback system called the baroreflex that returns blood pressure to a normal level as soon as there is a deviation from a typical pressure, such as, e.g., the mean arterial blood pressure.
• Prior extravascular placement techniques have involved invasive implantation procedures because the target tissue, such as a vagus nerve must be dissected to place and anchor the leads proximate the nerve tissue. Additionally, prior extravascular placement techniques commonly included lead electrode fixation at the lead distal end using, e.g., cuff electrodes, which may have deleterious effects over time including, e.g., nerve tissue necrosis. Techniques described herein provide for extravascular placement of medical leads for nerve tissue stimulation using implantation procedures with reduced invasiveness and without the need to anchor the leads at or very near their distal end. In general, the disclosed techniques include placing a portion of a medical lead having an electrode in an extravascular space within a sheath of tissue within a patient, and adjacent nerve tissue that is also within the sheath of tissue. The lead is anchored offset from the electrode at least partially outside of the sheath. As used herein, the term sheath of tissue generally refers to constraining connective tissue that holds together different biological structures within the body of a patient (e.g., a common carotid sheath).
• Intra or transvascular lead placement proximate the target nerve tissue, on the other hand, generally requires minimally invasive surgical techniques because the leads may be guided to the site through a blood vessel, e.g., a vein or artery, that may be readily accessible, e.g., transcutaneously through a small incision. Intra and transvascular lead placement techniques described herein may facilitate placing the distal end of the lead in close proximity of the target nerve tissue, the relative position of which with respect to an adjacent blood vessel may vary from patient-to-patient. Additionally, guided transvascular lead placement as described herein may avoid safety risks of such procedures including, e.g., piercing adjacent vessels, such as an artery.
• Some example intravascular techniques include structures and methods for deployment of one or more medical leads at a first location, testing stimulation at the first location, and, depending on the efficacy of the stimulation provided by electrodes on the leads at the first location, redeploying the leads to a second location. In one example, lead placement is improved by locating target nerve tissue with a sensor including, e.g., an intravascular ultrasound (IVUS) imaging system and/or measuring the efficacy of test electrical stimulation pulses from an electrode on the lead through a blood vessel adjacent the target tissue. After a placement location is determined, one or more leads including one or more electrodes may be deployed into the vessel and anchored to a vessel wall near the target nerve tissue. In some examples, the electrodes may be anchored with a fixation member that actively engages tissue of the blood vessel wall. In another intravascular placement example, an expandable and contractible generally cylindrical lead member is temporarily deployable for testing multiple electrode locations and combinations before deploying the member for chronic stimulation of the target nerve tissue.
• Transvascular techniques generally include improving lead placement by locating target nerve tissue with a sensor including, e.g., an IVUS imaging system, through a blood vessel adjacent the target tissue. After a placement location is determined, one or more leads including one or more electrodes may be deployed through the vessel wall and anchored to the vessel wall or other tissue near the target nerve tissue.
• The extra, intra, and transvascular lead placement techniques disclosed may also benefit, in some examples, from electrode pairs arranged in flanking, non-contacting relationship with the target nerve tissue. In one example, multiple leads are arranged longitudinally on opposing sides of the target nerve tissue, and include electrodes in non-contacting relationship with the target nerve tissue. In another example, one lead that includes multiple electrodes is employed such that at least two of the electrodes are arranged in flanking, non-contacting relationship with the target nerve tissue. Such flanking, non-contacting electrode arrangements may provide one or more anode and cathode electrode combinations for electrical stimulation across the target nerve tissue without the deleterious effects of tissue contacting techniques, such as may be caused by cuff electrodes.
• FIG. 1A is a conceptual diagram illustrating anexample therapy system10 that provides cardiac rhythm therapy and nerve tissue stimulation therapy topatient12.Therapy system10 includes implantable medical device (IMD)16, which is connected (or “coupled”) to leads18,20,22,28, andprogrammer24.IMD16 may be subcutaneously or submuscularly implanted in the body of a patient12 (e.g., in a chest cavity, lower back, lower abdomen, or buttocks of patient12).
• IMD16 may include a cardiac therapy module (not shown inFIG. 1A) and a neurostimulation module (not shown inFIG. 1A) enclosed withinouter housing44. The cardiac therapy module may generate and deliver cardiac rhythm management therapy toheart14 ofpatient12, and may include, for example, an implantable pacemaker, cardioverter, and/or defibrillator that provide therapy toheart14 ofpatient12 via electrodes coupled to one or more ofleads18,20, and22. In some examples, the cardiac therapy module may deliver pacing pulses, but not cardioversion or defibrillation pulses, while in other examples, the cardiac therapy module may deliver cardioversion or defibrillation pulses, but not pacing pulses. In addition, in further examples, cardiac therapy module may deliver pacing, cardioversion, and defibrillation pulses.IMD16 may deliver pacing that includes one or both of anti-tachycardia pacing (ATP) and cardiac resynchronization therapy (CRT).
• The neurostimulation module ofIMD16 may include a signal generator that generates and delivers electrical stimulation to a tissue site ofpatient12, e.g., tissue proximate a vagus nerve or other target nerve tissue ofpatient12. In some examples, the tissue site may include a peripheral nerve. As previously indicated, in some examples, the tissue site may include a nerve plexus that forms a node of intersecting nerves including, e.g., the cervical, brachial, lumbar, sacral, or solar plexus. Additionally, the techniques may be used for stimulation of nerve ganglia including, e.g., one or more ganglia of a nerve plexus. As an additional example, the techniques disclosed herein may be used in the treatment of vascular baroreceptors including, e.g., carotid baroreceptors. In the example shown inFIG. 1A, electrodes oflead28 are position to deliver electrical stimulation to targettissue site40 proximate a vagus nerve ofpatient12. The vagus nerve is primarily referred to herein as an example target nerve for neurostimulation therapy.
• In some examples, delivery of electrical stimulation to a nerve tissue site may provide cardiac benefits topatient12. For example, delivery of electrical stimulation to a peripheral nerve tissue site byIMD16 may help treat heart failure. In addition, delivery of electrical stimulation to a nerve ofpatient12 may help reduce or eliminate cardiovascular conditions such as bradycardia, tachycardia, unhealthy cardiac contractions, ischemia, inefficient heart pumping, inefficient collateral circulation ofheart14 or cardiac muscle trauma. In addition, delivery of electrical stimulation to a nerve may complement antitachycardia pacing or provide back-up therapy to cardiac therapy delivered byIMD16. In some examples,IMD16 may deliver electrical stimulation therapy to a nerve ofpatient12 via a lead implanted within vasculature (e.g., a blood vessel) ofpatient12. In other examples, stimulation may be delivered byIMD16 via a lead located in extravascular tissue, e.g., whenlead28 is not implanted within vasculature, such as within a vein or artery. Additional examples include transvascular placement of a lead from within a blood vessel ofpatient12 adjacent the target tissue site, through the wall of the blood vessel, and into an extravascular space, where the target nerve tissue may be located.
• In the example shown inFIG. 1A, the neurostimulation therapy module ofIMD16 delivers electrical stimulation therapy to a nerve ofpatient12 via a lead implanted within vasculature (e.g., a blood vessel) ofpatient12. In particular, lead28 is implanted such that electrodes oflead28 are positioned withinjugular vein46 proximate the vagus nerve (not shown). Stimulation of a parasympathetic nerve ofpatient12 may help slow intrinsic rhythms ofheart14, which may complement antitachyarrhythmia therapy (e.g., antitachycardia pacing, cardioversion or defibrillation) delivered byIMD16. In this way, neurostimulation therapy may help control a heart rate ofpatient12 or otherwise control cardiac function.
• In other examples, electrodes oflead28 may be positioned to deliver electrical stimulation to any other suitable nerve (e.g., a peripheral nerve) or nerve tissue inpatient12. In some examples, the neurostimulation module ofIMD16 may deliver electrical stimulation to other sympathetic or parasympathetic nerves, baroreceptors, hypoglossal nerve, carotid sinus, or a cardiac branch of the vagal trunk ofpatient12 in order to facilitate or compliment the delivery of therapy by the cardiac therapy module ofIMD16.
• InFIG. 1A, leads18,20, and22 extend into theheart14 ofpatient12 to sense electrical activity (electrical cardiac signals) ofheart14 and/or deliver electrical stimulation (cardiac therapy) toheart14. In particular, right ventricular (RV) lead18 extends through one or more veins (not shown), superior vena cava (not shown), andright atrium30, and intoright ventricle32. Left ventricular (LV)coronary sinus lead20 extends through one or more veins, the vena cava,right atrium30, and intocoronary sinus34 to a region adjacent to the free wall ofleft ventricle36 ofheart14. Right atrial (RA) lead22 extends through one or more veins and the vena cava, and intoright atrium30 ofheart14. In other examples,IMD16 is additionally or alternatively coupled to extravascular, e.g., epicardial or subcutaneous electrodes, via leads for cardiac sensing and/or stimulation.
• The cardiac therapy module may sense electrical signals attendant to the depolarization and repolarization ofheart14 via electrodes (not shown inFIG. 1A) coupled to at least one of theleads18,20,22. These electrical signals withinheart14 may also be referred to as cardiac signals or electrical cardiac signals. In some examples, the cardiac therapy module provides pacing pulses toheart14 based on the electrical cardiac signals sensed withinheart14. The configurations of electrodes used by the cardiac therapy module for sensing and pacing may be unipolar or bipolar. The cardiac therapy module may also provide defibrillation therapy and/or cardioversion therapy via electrodes located on at least one of theleads18,20,22 and one or more electrodes onhousing44 ofIMD16.IMD16 may detect arrhythmia ofheart14, such as fibrillation ofventricles32 and36, and deliver defibrillation therapy toheart14 in the form of electrical pulses via one or more ofleads18,20, and22. In some examples, the cardiac therapy module may be programmed to deliver a progression of therapies, e.g., pulses with increasing energy levels, until a fibrillation ofheart14 is stopped.IMD16 detects fibrillation employing one or more fibrillation detection techniques known in the art.
• The neurostimulation therapy module ofIMD16 may provide a programmable stimulation signal (e.g., in the form of electrical pulses or a continuous signal) that is delivered to targetstimulation site40 by implantablemedical lead28, and more particularly, via one or more stimulation electrodes carried bylead28.Proximal end28A oflead28 may be both electrically and mechanically coupled toconnector42 ofIMD16 either directly or indirectly (e.g., via a lead extension). In particular, conductors disposed in the lead body oflead28 may electrically connect stimulation electrodes (and sense electrodes, if present) oflead28 toIMD16. In some examples, the neurostimulation therapy module ofIMD16 may be electrically coupled to more than one lead directly or indirectly (e.g., via a lead extension).
• In the example ofFIG. 1A, one or more electrodes oflead28 are intravascularly implanted inpatient12 proximate to targettissue stimulation site40, e.g., proximate to a vagus nerve (not shown). In particular, one or more neurostimulation electrodes oflead28 are implanted withinjugular vein46. Generally speaking, implantinglead28 near the vagus nerve ofpatient12 may be useful for delivering neurostimulation therapy to the vagus nerve without requiringlead28 to be subcutaneously implanted inpatient12. Implantinglead28 intravascularly withinjugular vein46 may thereby be useful for reducing trauma topatient12, e.g., becauselead28 is not tunneled through subcutaneous tissue fromIMD16 to targetsite40. As described in greater detail with reference toFIGS. 4-22, in other examples according to this disclosure, lead28 may be extravascularly or transvascularly placed proximate targettissue stimulation site40, e.g., proximate a vagus nerve ofpatient12.
• The distal portion oflead28 may include one or more electrodes (not shown) for delivering neurostimulation to targetstimulation site40. Various electrode configurations oflead28 are described in further detail with respect toFIGS. 2 and 3. In some examples, lead28 may also carry sense electrodes (not shown) to permitIMD16 to sense electrical signals, such as electrical cardiac signals or electrical nerve signals from the vagus nerve or other nerve tissue at which therapy is directed.Lead28 may also carry one or more sensors including, e.g., sense electrodes, pressure sensors, ultrasound sensors, motion sensors, acoustic sensors (heart rate), optical sensors, blood oxygen sensors, posture state sensors, respiration sensors, venous biomarker sensors, temperature sensors or other devices that may detect physiological signals ofpatient12 indicative of the efficacy of neurostimulation therapy delivered to the patient by stimulation electrodes.
• In some examples,IMD16 may deliver an electrical stimulation signal via one or more of the electrodes oflead28, and analyze a physiological signal to detect a response to the stimulation signal. In one such example,IMD16 analyzes an electrical nerve signal to detect a response to the stimulation signal. The characteristic of the electrical nerve signal that indicates the desired response to the delivery of the electrical stimulation signal by the neurostimulation therapy module ofIMD16 may be, for example, an amplitude or frequency of the electrical signal. The target characteristic of the electrical nerve signal may be determined by a clinician at any suitable time whenlead28 is known to be in the desired location withinpatient12, e.g., immediately afterlead28 is implanted withinpatient12.
• The electrical nerve signal may be an electrical signal generated by a nerve, such as the target nerve for the neurostimulation therapy or a branch thereof, in response to an electrical stimulation signal delivered by the electrodes oflead28. The response to the electrical stimulation signal may indicate, for example, whether the neurostimulation signal captured the nerve, and, therefore, is within a desired distance of the nerve. In the example shown inFIG. 1A, the target nerve is a vagus nerve, however, other types of nerves are contemplated for the neurostimulation therapy. The electrical nerve signal may be sensed between two or more electrodes oflead28.IMD16 may analyze the electrical nerve signal for a response, for example, by measuring an amplitude of the electrical nerve signal and comparing the determined value to a threshold value. In this case, the electrical nerve signal may have a baseline amplitude value and a response to the stimulation signal may be characterized by a spike in amplitude. The nerve response may be characterized by an amplitude or other characteristics of a sensed electrical signal.
• In the context of lead placement techniques disclosed herein, sensed physiological signals may be used to determine the efficacy of neurostimulation delivered by electrodes onlead28 to target nerve tissue. In some examples, lead28 may be intra, extra, or transvascularly placed proximate the nerve tissue and electrodes onlead28 may deliver test stimulation pulses to the nerve tissue in order to test the placement oflead28 withinpatient12 relative to the nerve tissue. Various physiological signals may be observed to measure the efficacy of the test stimulation, and thereby the need to repositionlead28 relative the target nerve tissue. In some examples, test treatment efficacy may be indicated by, e.g., ECG, heart rate, blood pressure, blood flow, blood oxygen content, blood biomarker content, cardiac output, and/or breathing, ofpatient12. Additionally, T-wave morphology, heart rate variability, contractility, and atrioventricular (AV) intervals may be observed as an indication of test treatment efflcacy. These and other physiological signals may be detected in a variety of ways including sensing the signals using sense electrodes, pressure sensors, ultrasound sensors, motion sensors or other devices. In other examples, physiological reactions ofpatient12 may be observed or measured by, e.g., a clinician.
• In the case one or more sensors are employed to detect physiological signals ofpatient12, such devices may be arranged in a variety of locations depending on device configuration and the particular signal being detected. For example, the efficacy of electrical stimulation of a vagus nerve may be measured by an accelerometer arranged in the neck ofpatient12 that determines if stimulation of neck muscles or the phrenic nerve is occurring with or instead of stimulation of a vagus nerve. In another example, a pressure sensor arranged coincident with or connected to lead28 may measure blood pressure by detecting the pressure within a vessel in which lead28 is placed. A pressure sensor, or other type of physiological feedback sensor, may also, in some examples, be connected to a delivery catheter configured to placelead28 withinpatient12. In still another example, a cardiac therapy module included inIMD16 may employ one or more electrodes arranged on or withinheart14 ofpatient12 to, e.g., to monitor electrical activity ofheart14 via an electrogram (EGM) or electrocardiogram (ECG) signal. In other examples, venous biomarker sensors configured to sense, e.g., inflammation markers or catecholamines may be used to measure the effect of the stimulation and provide feedback toIMD16.
• The extra, intra, and transvascular lead placement techniques described herein are applicable for implantation of a variety of implantable therapy systems including, e.g.,system10 ofFIG. 1A, as well as systems that do not deliver cardiac stimulation and/or provide cardiac sensing, or, as with the example ofFIG. 1B, deliver cardiac therapy using a device that is separate from and in addition to an implantable neurostimulator.
• As illustrated inFIG. 1A,system10 may include aprogrammer24.IMD16 may transmit information to and receive information fromprogrammer24 related to the operation ofIMD16 and/or the delivery of therapy byIMD16 topatient12. Upon receiving the information,programmer24 may upload the received information to a remote server, from which a clinician may access the data (such as a remote server of the CareLink Network available from Medtronic, Inc. of Minneapolis, Minn.). A clinician may also access the information directly by interacting withprogrammer24. Furthermore, the clinician may program various aspects of the operation ofIMD16 remotely by accessing a remote server that communicates withIMD16 via a network andprogrammer24, or locallyprogram IMD16 by physically interacting with programmer. In some examples, the clinician may interact withprogrammer24 to, e.g., program select values for operational parameters ofIMD16.
• In some examples,programmer24 may be a handheld computing device or a computer workstation. The user may useprogrammer24 to program aspects of the neurostimulation module. The therapy parameters for the neurostimulation module ofIMD16 may include an electrode combination for delivering neurostimulation signals, as well as an amplitude, which may be a current or voltage amplitude, and, if the neurostimulation module delivers electrical pulses, a pulse width, and a pulse rate for stimulation signals to be delivered topatient12. The electrode combination may include a selected subset of one or more electrodes located onimplantable lead28 coupled toIMD16 and/or a housing ofIMD16. The electrode combination may also refer to the polarities of the electrodes in the selected subset. By selecting particular electrode combinations, a clinician may target particular anatomic structures withinpatient12. In addition, by selecting values for amplitude, pulse width, and pulse rate, the physician can attempt to generate an efficacious therapy forpatient12 that is delivered via the selected electrode subset.
• As another example,programmer24 may be used by a user, e.g., a clinician while a medical lead is placed within patient in accordance with this disclosure to retrieve or view sensor feedback during the implantation of the lead. In one example, a physician usesprogrammer24 to retrieve and/or view physiological signals sensed by one or more sensors in response to test electrical stimulation pulses delivered topatient12 during the placement oflead12 adjacent a vagus nerve. In this manner, the physician employsprogrammer24 to determine the efficacy of the test stimulation delivered bylead28, and thereby the position oflead28 relative to the vagus nerve. In another example, the physician may also useprogrammer24 to view an imaging field produced by an IVUS imaging system connected to a delivery catheter used to placelead28, and electrodes connected thereto intra or transvascularly withinpatient12. In this manner, the physician may employprogrammer24 to view, in real time, the placement oflead28 withinpatient12 relative to target nerve tissue and a blood vessel in which or through which the lead is placed.
• Programmer24 may communicate withIMD16 via wireless communication using any techniques known in the art. Examples of communication techniques may include, for example, low frequency or radiofrequency (RF) telemetry, but other techniques are also contemplated. In some examples,programmer24 may include a programming head that may be placed proximate to the patient's body near theIMD16 implant site in order to improve the quality or security of communication betweenIMD16 andprogrammer24.
• FIG. 1B is a conceptual diagram illustrating anotherexample therapy system11 that includes separate implantable cardiac device (ICD)17 and implantableelectrical stimulator26.ICD17 is connected to leads18,20, and22, andprogrammer24, whileelectrical stimulator26 is coupled to lead28 and may be communicatively connected to bothICD17 andprogrammer24.ICD17 may be, for example, a device that provides cardiac rhythm management therapy toheart14, and may include, for example, an implantable pacemaker, cardioverter, and/or defibrillator, as described above with reference toIMD16.
• In some examples,ICD17 may, in addition to or instead of delivering cardiac rhythm management therapy toheart14, sense electrical cardiac signals ofheart14 and/or other physiological parameters of patient12 (e.g., blood oxygen saturation, blood pressure, temperature, heart rate, respiratory rate, and the like), and store the electrical cardiac signals and/or other physiological parameters ofpatient12 for later analysis by a clinician. In such examples,ICD17 may be referred to as a patient monitoring device. Examples of patient monitoring devices include, but are not limited to, the Reveal Plus Insertable Loop Recorder, which is available from Medtronic, Inc. of Minneapolis, Minn. For ease of description,ICD17 will be referred to herein as a cardiac rhythm management therapy delivery device.
• Therapy system11 also includes implantableelectrical stimulator26, which is coupled to lead28.Electrical stimulator26 may also be referred to as an implantable neurostimulator (“INS”)26.INS26 may be any suitable implantable medical device (IMD) that includes a signal generator that generates electrical stimulation signals that may be delivered via one or more electrodes onlead28 to a nerve tissue site ofpatient12, e.g., tissue proximate a vagus nerve.
• In the example shown inFIG. 1B, electrodes oflead28 are positioned outside the vasculature ofpatient12 to deliver electrical stimulation to a vagus nerve (not shown) ofpatient12. As described above, in other examples, stimulation may be delivered to a nerve tissue site via electrodes of an intravascular lead that is implanted within vasculature. In still other examples, stimulation may be delivered to a nerve tissue site withinpatient12 via electrodes of a transvascular lead that is guided proximate the target tissue site intravascularly, i.e., through a vein, artery, or other blood vessel and then pierces a wall of the vessel to be arranged adjacent the target tissue outside of the blood vessel.
• In the example shown inFIG. 1B, the components ofICD17 andINS26 are enclosed in separate housings, such thatICD17 andINS26 are physically separate devices. In contrast to the example ofFIG. 1A in which the functionality ofICD17 andINS26 are be performed byIMD16 that includes both a cardiac therapy module and an electrical stimulation therapy module. In applications in which cardiac and neurostimulation therapy operate cooperatively or sensing feedback is provided fromheart14 or a nerve tissue site withinpatient12,ICD17 andINS26 ofFIG. 1B may communicate with one another via one or more wireless communication techniques instead of being directly linked within the same device housing as inIMD16 oftherapy system10 shown inFIG. 1A. For example,INS26 may include one or more sensors that analyze an electrical nerve signal to detect a response to the stimulation signal delivered byICD17 and/orINS26 topatient12.ICD17 andINS26 may communicate wirelessly using, e.g., low frequency or radiofrequency (RF) telemetry.
• FIG. 2 is a functional block diagram of an example configuration ofIMD16 ofFIG. 1A, which includesprocessor100,memory102,cardiac therapy module104,neurostimulation therapy module106,telemetry module108, andpower source110.Cardiac therapy module104 includessignal generator112 andsensing module114.Neurostimulation therapy module106 includessignal generator116 andsensing module118. The components ofIMD16 shown inFIG. 2 may be substantially enclosed within a common, hermetically sealedouter housing44 ofIMD16. In other examples including the example shown inFIG. 1B, components for carrying out the functions ofcardiac therapy module104 andneurostimulation therapy module106 may be arranged in separate communicatively connected devices. Althoughcardiac therapy module104 andneurostimulation therapy module106 are illustrated as separate modules inFIG. 4, in some examples,cardiac therapy module104 andneurostimulation module106 and their respective components may share circuitry. For example, signalgenerators112 and116 may share common circuitry, e.g., a stimulation engine, charging circuitry, capacitors, and the like. Additionally, in some examples in whichcardiac therapy module104 andneurostimulation module106 deliver stimulation in alternation,cardiac therapy module104 andneurostimulation module106 may share some or all stimulation generation circuitry. Similarly, in some examples, sensingmodules114 and118 may also share common circuitry, such as an analog-to-digital converter and the like.
• Memory102 includes computer-readable instructions that, when executed byprocessor100,cause IMD16 andprocessor100 to perform various functions attributed toIMD16 andprocessor100 herein. InFIG. 2,memory102 includescardiac programs122 thatcardiac therapy module104 uses for generating cardiac rhythm therapy for delivery toheart14, andneurostimulation programs124 that neurostimulationmodule106 uses for generating neurostimulation therapy for delivery to targettissue site40.Memory102 may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital media.
• Processor100 may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or integrated logic circuitry. In some examples,processor100 may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed toprocessor100 herein may be embodied as software, firmware, hardware or any combination thereof.Processor100 may controlcardiac therapy module104 to deliver stimulation therapy according to a selected one or more ofcardiac programs122 stored inmemory102. In addition,processor100 may controlneurostimulation module106 to delivering stimulation therapy according to a selected one or more ofneurostimulation programs124 stored inmemory102. Specifically,processor100 may controlcardiac therapy module104 and/orneurostimulation module106 to deliver electrical signals via electrode combinations with amplitudes, frequency, electrode polarities, and, in the case of stimulation pulses, pulse widths specified by the selected one or more cardiac andneurostimulation therapy programs122,124, respectively.
• In the example shown inFIG. 2,cardiac therapy module104 is electrically connected toelectrodes50,52,54,56,58,60,72,74, and76 ofleads18,20, and22 andhousing electrode68, andneurostimulation module106 is electrically connected to electrodes80-83 oflead28 andhousing electrode68. In other examples,cardiac therapy module104 andneurostimulation module106 may be coupled to any suitable number of electrodes, which may comprise a greater number of electrodes or a fewer number of electrodes than that shown in the example ofFIG. 2.
• Cardiac therapy module104 is configured to generate and deliver cardiac rhythm therapy toheart14. For example,signal generator112 ofcardiac therapy module104 may generate and deliver cardioversion or defibrillation shocks and/or pacing pulses toheart14 via a selected combination ofelectrodes50,52,54,56,58,60,72,74, and76 andhousing electrode68.Signal generator112 ofcardiac therapy module104 is electrically coupled toelectrodes50,52,54,56,58,60,72,74, and76, e.g., via conductors of therespective lead18,20,22, or, in the case ofhousing electrode68, via an electrical conductor disposed withinhousing44 ofIMD16.
• Sensing module114 monitors signals from at least one ofelectrodes50,52,54,56,58,60,72,74, and76 in order to monitor electrical activity ofheart14, e.g., via an EGM or ECG signal.Sensing module114 may also include a switching module (not shown inFIG. 4) to select a particular subset of available electrodes to sense heart activity. In this manner,sensing module114 may detect R-waves, P-waves, or other cardiac electrical activity, and provide indications of their occurrence toprocessor100. In some examples, processor may analyze a digitized the EGM or ECG to detect these or other morphological features of the EGM or ECG, to determine heart rates or intervals (e.g., R-R intervals) or sizes of features such as T-waves or QRS complexes, or provide any other known cardiac sensing and monitoring functionality.
• Neurostimulation module106 is configured to generate and deliver electrical stimulation therapy to a target site withinpatient12 proximate nerve tissue, e.g., in order to modulate an autonomic nervous system or vascular tone. Example stimulation sites forneurostimulation module106 include, but are not limited to, tissue proximate a vagus nerve or braches of a vagus nerve ofpatient12. For example,signal generator116 may generate stimulation signals that are delivered to a tissue site proximate a vagus nerve via a selected combination of electrodes80-83 oflead28 and/orhousing electrode68. The stimulation signals may be pulses as primarily described herein, or continuous time signals, such as sine waves.
• Signal generator116 may be a single or multi-channel signal generator. In particular,signal generator116 may be capable of delivering, a single stimulation pulse, multiple stimulation pulses, or a continuous signal at a given time via a single electrode combination or multiple stimulation pulses at a given time via multiple electrode combinations. In some examples, however,neurostimulation therapy module106 may be configured to deliver multiple channels on a time-interleaved basis. In this case,neurostimulation therapy module106 may include a switching module (not shown) that serves to time division multiplex the output of the signal generator across different electrode combinations at different times to deliver multiple programs or channels of stimulation energy topatient12.
• Sensing module118 ofneurostimulation module106 monitors signals from at least one of electrodes80-83 oflead28 andhousing electrode68 in order to monitor electrical activity of the target nerve tissue, e.g. nerve signals of a vagus nerve. For example, the amount of afferent and efferent signals of nerve fibers can be monitored. In one such example, the nerve signals of the left vagus nerve ofpatient12 can be compared to the right vagus nerve and therapy may be delivered byneurostimulation module106 and/orcardiac therapy module104 as commanded byprocessor100 based at least in part upon this comparison of sensed nerve tissue traffic. Conversely, in the context of lead placement techniques described herein, therapy may be delivered to a vagus nerve (e.g. left or right, or both) by one or more of electrodes80-83 andsensing module118 ofneurostimulation module106 and/orsensing module114 ofcardiac therapy module104 as commanded byprocessor100 may monitor afferent and efferent signals of vagal nerve fibers to measure the efficacy of the therapy.
• Telemetry module108 includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as programmer24 (FIG. 1). Under the control ofprocessor100,telemetry module108 may receive downlink telemetry from and send uplink telemetry toprogrammer24 with the aid of an antenna, which may be internal and/or external.Processor100 may provide the data to be uplinked toprogrammer24 and the control signals for the telemetry circuit withintelemetry module108, e.g., via an address/data bus. In some examples,telemetry module108 may provide received data toprocessor100 via a multiplexer.
• The various components ofIMD16 are coupled topower source100, which may include a rechargeable or non-rechargeable battery or a supercapacitor. A non-rechargeable battery may be selected to last for several years, while a rechargeable battery may be inductively charged from an external device, e.g., on a daily or weekly basis.Power source100 may also include an external or a subcutaneously implanted RF transmitter that is configured to deliver power via radio frequency pulses to a receiver arranged withIMD16 or one of the leads and/or electrodes ofcardiac therapy module104 andneurostimulation therapy module106. In other examples, some part ofIMD16, or one of the leads or electrodes may be composed of a piezoelectric material that can generate current when excited mechanically by ultra sound waves transmitted from an external or implanted source.
• In some examples, data generated by sensingmodule114 orsensing module118 and stored inmemory102 may be uploaded to a remote server, from which a clinician or another user may access the data to determine whether a potential sensing integrity issue exists. An example of a remote server includes the CareLink Network, available from Medtronic, Inc. of Minneapolis, Minn. An example system may include an external device, such as a server, and one or more computing devices that are coupled toIMD16 andprogrammer24 via a network.
• In addition to the examples ofFIGS. 1A,1B, and2 including cardiac therapy and neurostimulation therapy implemented in a single or separate devices, examples according to this disclosure also include a standalone INS device implanted withinpatient12 and configured to function in a manner consistent with the description ofneurostimulation therapy module106 ofIMD16 orINS26 shown inFIGS. 1A and 2, and1B respectively.
• FIG. 3 is block diagram ofexample programmer24 ofFIGS. 1A and 1B. As shown inFIG. 3,programmer24 includesprocessor130,memory132, user interface134,telemetry module136, andpower source138.Programmer24 may be a dedicated hardware device with dedicated software for programming one or more ofIMD16,ICD17, orINS26. Alternatively,programmer24 may be an off-the-shelf computing device running an application that enablesprogrammer24 to program one or more ofIMD16,ICD17, orINS26. For convenience and clarity, the description ofFIG. 3 will be made with reference to the operation ofprogrammer24 withIMD16. However, the components and functions ofprogrammer24 described herein are equally applicable to use withICD17,INS26 or any other implantable medical device that may benefit from the functions provided by an external programming device such asprogrammer24.
• A user may useprogrammer24 to select therapy programs (e.g., sets of stimulation parameters), generate new therapy programs, modify therapy programs through individual or global adjustments or transmit the new programs to IMD16 (FIG. 1A). The therapy programs may be for either or bothcardiac therapy module104 and neurostimulation module106 (FIG. 2). A clinician, e.g., may interact withprogrammer24 via user interface134, which may include a display to present a graphical user interface to a user, and a keypad or another mechanism for receiving input from a user.
• Processor130 can take the form of one or more microprocessors, DSPs, ASICs, FPGAs, programmable logic circuitry, or the like, and the functions attributed toprocessor130 herein may be embodied as hardware, firmware, software or any combination thereof.Memory132 may store instructions that causeprocessor130 to provide the functionality ascribed toprogrammer24 herein, and information used byprocessor130 to provide the functionality ascribed toprogrammer24 herein.Memory132 may include any fixed or removable magnetic, optical, or electrical media, such as RAM, ROM, CD-ROM, hard or floppy magnetic disks, EEPROM, or the like.Memory132 may also include a removable memory portion that may be used to provide memory updates or increases in memory capacities. A removable memory may also allow patient data to be easily transferred to another computing device, or to be removed beforeprogrammer24 is used to program therapy for another patient.Memory132 may also store information that controls therapy delivery byIMD16, such as stimulation parameter values.
• Programmer24 may communicate wirelessly withIMD16, such as using RF communication or proximal inductive interaction. This wireless communication is possible through the use oftelemetry module136, which may be coupled to an internal antenna or an external antenna. An external antenna that is coupled toprogrammer24 may correspond to the programming head that may be placed proximate to the patient's body near theIMD16 implant site, as described above with reference toFIG. 1A.Telemetry module136 may be similar totelemetry module108 of IMD16 (FIG. 2).
• Telemetry module136 may also be configured to communicate with another computing device via wireless communication techniques, or direct communication through a wired connection. Examples of local wireless communication techniques that may be employed to facilitate communication betweenprogrammer24 and another computing device include RF communication according to the 802.11 or Bluetooth specification sets, infrared communication, e.g., according to the IrDA standard, or other standard or proprietary telemetry protocols. In this manner, other external devices may be capable of communicating withprogrammer24 without needing to establish a secure wireless connection.
• Power source138 delivers operating power to the components ofprogrammer24.Power source138 may include a battery and a power generation circuit to produce the operating power. In some examples, the battery may be rechargeable to allow extended operation ofprogrammer24.
• FIGS. 4 and 5 are schematic illustrations depicting relevant anatomy for lead placement techniques described herein.FIG. 4 illustratesvagus nerve150 including many branches, such as pharyngeal andlaryngeal branches152,cardiac branches154, as well as the gastric and pancreaticoduodenal branches (not specifically labeled inFIG. 4). The illustration ofFIG. 5 is a cross section through the neck ofpatient12 that showscarotid sheath156 in which is contained internaljugular vein158,carotid artery160, and left andright vagus nerves150L and150R respectively.Vagus nerve150 originates in the brainstem, runs in the neck throughcarotid sheath156 withjugular vein158 and commoncarotid artery160, and then adjacent to the esophagus to the thoracic and abdominal viscera.Vagus nerve150 provides the primary parasympathetic nerve to the thoracic and most of the abdominal organs. For example,vagus nerve150 provides parasympathetic innervation to the heart, and stimulation of the nerve has been demonstrated to drive the parasympathetic nervous system and thereby overcome an accelerated sympathetic tone, which may be exhibited by patients suffering from various tachycardia conditions, as well as heart failure. In one such tachycardia application, the efferent fibers of the vagus nerve, such as one or more superior and/or inferior cardiac branches may be electrically stimulated to manage the accelerated arrhythmia. Vagal nerve stimulation may also have afferent effects that result in nerve reflex changes that affect heart rate. In addition to heart innervations,vagus nerve150 is responsible for such varied tasks as gastrointestinal peristalsis, sweating, as well as muscle movements related to speech. Electrical stimulation ofvagus nerve150 may be useful in treating, not only heart failure and arrhythmia conditions, but also various other conditions including, e.g., depression, epilepsy, and various gastrointestinal conditions. To determine the need for and/or response to nerve tissue stimulation according to methods and systems disclosed herein, ECG, heart rate, blood pressure, blood flow, cardiac output, and/or breathing, for instance, ofpatient12 can be sensed. Such patient feedback information can be gleaned from, e.g., clinician observation, as well as employing one of implantable cardiac device (ICD)17 shown inFIG. 1B orcardiac therapy module104 shown inFIG. 2. Again, although the techniques disclosed herein are described generally in the context of stimulation of one of the vagus nerves on the vagal nerve trunk in the neck of a human patient, the methods and systems disclosed are also applicable to stimulation and treatment of other nerve tissues that are located in diverse locations including, e.g., baroreceptors, hypoglossal nerves, and nerve plexus and ganglia.
• In addition to various biological structures ofpatient12,FIG. 5 shows intra and extravascularly placed leads29′ and29″ respectively.Medical lead29 is used for purposes of describing placement techniques according to this disclosure. In general, lead29 may correspond to lead28 shown inFIGS. 1A and 1B above.Intravascular lead29′ is arranged within internaljugular vein158, whileextravascular lead29″ is arranged withincarotid sheath156,adjacent vagus nerve150. In addition to intra and extravascular leads29′ and29″ shown inFIG. 5, examples according to this disclosure include transvascular placement oflead29 such that the lead passes from within a blood vessel ofpatient12 through a wall of the vessel to terminate adjacent a target nerve tissue stimulation site. For example, lead29 may be guided proximate a target site intravascularly through internaljugular vein158 and then pierce a wall ofjugular vein158 to be arrangedadjacent vagus nerve150. Although the examples disclosed herein are generally described in the context of stimulating vagal nerves in the neck ofpatient12, lead29 and electrodes attached thereto may also be arranged for vagal nerve stimulation in, e.g., the thorax, and/or adjacent to the esophagus.
• Extravascular lead placement techniques according to this disclosure provide placement of leads for nerve tissue stimulation and/or nerve signal sensing using implantation procedures with reduced invasiveness and without the need to anchor the leads at or very near their distal end. In general, the disclosed techniques include placing a portion of a medical lead having an electrode in an extravascular space within a sheath of tissue within a patient, and adjacent nerve tissue that is also within the sheath of tissue. The lead is anchored offset from the electrode at least partially outside of the sheath.
• FIGS. 6-8 illustrate examples of extravascular lead placement techniques in the context of vagal nerve stimulation in a human patient.FIG. 6 is a schematicillustration depicting lead29 extravascularly placedadjacent vagus nerve150 withincarotid sheath156 inpatient12. After or during placement, lead29 may be connected toIMD16 orINS26 similar to lead28 shown inFIGS. 1A and 1B respectively.FIG. 7 is a flow chart illustrating an example method of placinglead29 in accordance with the example ofFIG. 6. The example method ofFIG. 7 generally includes placing a portion of a medical lead having an electrode electrically connected thereto in an extravascular space adjacent nerve tissue within a sheath of tissue within a patient (180), anchoring the lead offset from the electrode outside of the sheath, (182), and stimulating the nerve tissue (184). One example of the method illustrated inFIG. 7 will be described in the context of the example lead placement shown inFIG. 6.
• The arrangement shown inFIG. 6 includeslead29,electrodes170, andanchor172.Electrodes170 are connected to and arranged toward a distal end oflead29. The example ofFIG. 6 also includes biasingmember176 anddeployable lobe member178 connected to lead29 to bias and/or stabilizelead29 andelectrodes170 towardvagus nerve150. Although the example ofFIG. 6 shows fourelectrodes170, other examples may include fewer or more electrodes connected to lead29 and, in some cases, other leads in addition to lead29. In some examples,electrodes170 may include multiple types including, e.g., electrode pads on a paddle lead, circular (e.g., ring) electrodes surrounding the body of leads16, conformable electrodes, segmented electrodes, or any other type of electrodes capable of forming unipolar, bipolar or multipolar electrode configurations for delivering nerve tissue stimulation therapy topatient12. In some examples including ring electrodes,electrodes170 may be arranged onlead29 with part of the rings electrically insulated to limit the spread of the stimulating field so that only a portion of the electrodes and electrical stimulation may be directed atvagus nerve150.
• The distal end oflead29 to whichelectrodes170 are attached is arranged withincarotid sheath156,adjacent vagus nerve150.Biasing member176 anddeployable lobe member178 are arranged at the distal end oflead29 and bias lead29 towardvagus nerve150 by exerting a force on surrounding tissue including, e.g., internaljugular vein158. A proximate end of lead29 (not shown inFIG. 6) may be connected to IMD16 (seeFIG. 1A).Anchor172 is connected to lead29 offset from the distal end oflead29 outside ofcarotid sheath156.Anchor172 may be any suitable fixation element that stabilizes the placement oflead29 andelectrodes170 withinsheath156adjacent vagus nerve150. For example,anchor172 may be one of a variety of sutureless fixation elements connected to lead29 that are configured to engage tissue ofpatient12 outside ofcarotid sheath156. In one example, one or more tines or barbs may protrude fromlead29 to pierce and thereby attachlead29 to tissue ofpatient12 outside ofsheath156. In addition to or instead of sutureless anchors,anchor172 may include various fixation elements that engagelead29 and are configured to be sutured by a clinician to the tissue ofpatient12 outside ofcarotid sheath156. Additionally, in some examples,anchor172 may include a sleeve configured to receivelead29 therethrough and tabs protruding from the sleeve that may passively engage or be sutured to tissue ofpatient12. In some examples, such sleeve anchors may be used to seal a tissue access site, such asincision174 incarotid sheath156.Anchor172 is offset from the most proximal ofelectrodes172 by a distance D. In some examples, the offset distance D ofanchor172 from the most proximal ofelectrodes172 is in the range from and including approximately 1 cm to and including approximately 15 cm. In other examples, the offset distance D may be in the range from and including approximately 1 cm to and including approximately 2 cm.
• In practice, a variety of techniques may be employed toextravascularly place lead29 withincarotid sheath156adjacent vagus nerve150. In the example ofFIG. 6, the portion ofcarotid sheath156 and surrounding tissue ofpatient12 shown may be exposed by an incision in the neck of the patient. However, becauselead29 is not anchored at the distal end that is arranged withincarotid sheath156, all of or even a portion ofvagus nerve150 need not be dissected fromsheath156. Instead, lead29 may be guided through a relativelysmall incision174 incarotid sheath156 to place the distal end oflead29 includingelectrodes170adjacent vagus nerve150.Lead29 may be placed throughincision174 withincarotid sheath156 using a variety of introducer elements including, e.g., a catheter and/or a guide wire to stabilize and guide the placement oflead29adjacent vagus nerve150.Lead29 may be stiffened withincarotid sheath156 by, e.g., the guide wire or a stylus. Additionally, the distal end oflead29 includingelectrodes170 may be biased towardvagus nerve150 using biasingmember176.Biasing member176 may be, e.g. an inflatable or otherwise expandable structure including, e.g. a stent-like member or a balloon as schematically illustrated inFIG. 6. In other examples, biasingmember176 may be static, e.g. protruding tines, or retractable and/or deployable, e.g. one or more elongated splines or lobes that deflect away fromlead29 when placed under tension. For example, in addition to biasingmember176, the example ofFIG. 6 includesdeployable lobe member178 including a plurality of deployable lobes that protrude from and are circumferentially distributed aboutlead29.
• An example ofdeployable lobe member178 may be the Attain® StarFix™ fixation element included in the over-the-wire lead Model 4195 developed and sold by Medtronic, Inc. of Minneapolis, Minn. The design of this fixation element allows clinicians to place and stabilize elongated medical electrical leads within patients. The StarFix™ element generally includes a number of deployable lobes that are formed lengthwise on an insulating sheath that surrounds the medical lead by pairs of elongated, parallel cuts or slits. The deployable lobes are formed by the material between the elongated, substantially parallel slits. The spacing between the slits generally defines the width of the deployable lobe formed therebetween. Accordingly, the rigidity of each lobe may be increased or decreased by increasing or decreasing the distance between the parallel slits that define the lobe. The rigidity of the lobes may also be altered by using different types of materials and changing the thickness of the insulating sheath in which the slits are cut to produce the deployable lobes. The StarFix™ lobes are deployed by pushing the insulating sheath on either side of the parallel slits. The pushing action causes the sheath to become compressed, thus causing the extension of the deployable lobes outwardly. As necessary, the lobes can be relaxed to allow for acute repositioning of the lead by withdrawing a coupling member so as to reduce compression on the lobe structure. The StarFix™ lead technology provides reliable fixation of medical leads that can be readily customized to fit a variety of anatomical dimensions. Examples of deployable lobe members for biasing and/or stabilizinglead29 withincarotid sheath156 include those described in U.S. Patent Publication No. 2004/0176782 A1, to George H. Hanse et al., filed Mar. 3, 2004, titled “METHOD AND APPARATUS FOR FIXATING AN IMPLANTABLE MEDICAL DEVICE,” the entire content of which is incorporated herein by reference.
• The placement oflead29adjacent vagus nerve150 may be stabilized byanchor172. As explained above,anchor172 may be any suitable fixation element that stabilizes the placement oflead29 andelectrodes170 withinsheath156adjacent vagus nerve150. In one example,anchor172 includes one or more tines protruding fromlead29 offset from the most proximate ofelectrodes170 by a distance D. The tines ofanchor172 may be angled with respect to lead29 and flexible such that aslead29 is guided forward through tissue ofpatient12 the tines lay down against an exterior surface of the lead and do not engage the tissue of the patient. After placement, lead29 may be backed slightly out through the tissue ofpatient12 to cause the tines ofanchor172 to pull away from the lead and catch and pierce the tissue ofpatient12, thereby connectinglead29 to the tissue.
• In other examples,anchor172 may include a sleeve anchor configured to receivelead29 therethrough and passively engage or be sutured to tissue ofpatient12.FIGS. 8A-8B show two example sleeve anchors200 and202 respectively. Both anchors200 and202 haveinterior bore204 that is sized to receivelead29 therethrough.Anchors200 and202 also includetabs206 and208 respectively protruding away frombore204.Tabs206 ofanchor200 are configured to passively engage tissue ofpatient12 to substantially fix the anchor and thereby stabilize the placement oflead29.Tabs208 ofanchor202, on the other hand, includes suture-receivingapertures210 that may receive sutures to attachanchor202 to tissue ofpatient12 and thereby stabilize the placement oflead29.Anchor202 also includesribs212, which may be adapted to inhibit longitudinal movement ofanchor202 and/or lead29 with respect to tissue ofpatient12 to further stabilize the placement oflead29. In some examples, sleeve anchors200 and202 may be used to seal a tissue access site, such asincision174 incarotid sheath156.
• In addition to the above described examples,anchor172 may include deployable lobes that are arranged to deploy on either side ofincision174 incarotid sheath156 to stabilize the placement oflead29adjacent vagus nerve150.FIG. 8C showsdeployable lobe member178 arranged atincision174 incarotid sheath156 to stabilize placement oflead29. As with the example arrangement shown inFIG. 6,deployable lobe member178 inFIG. 8C includes a plurality of deployable lobes that protrude from and are circumferentially distributed aboutlead29. InFIG. 8C, however,lobe member178 is arranged with respect toincision174 such that the incision incarotid sheath156 lies between two sets ofdeployable lobes178A,178B ofdeployable lobe member178. Deployable lobe set178A liesadjacent incision174 outside ofcarotid sheath156, while set178B lies inside the sheath. Upon deployment of lobe sets178A and178B on either side ofincision174,deployable lobe member178 stabilizes the placement oflead29 andelectrodes170 withinsheath156adjacent vagus nerve150. As with the example ofFIG. 6, an example ofdeployable lobe member178 arranged as in the example ofFIG. 8C may be the Attain® StarFix™ fixation element developed and sold by Medtronic, Inc. of Minneapolis, Minn.
• A portion oflead29 extending fromanchor172 in the examples ofFIGS. 6-8C may be guided to connect withIMD16. In one example, lead29 may be guided intravascularly to an implantation location ofIMD16 withinpatient12. In other examples, lead29 may be tunneled through tissue ofpatient12 to be connected toIMD16. Although the example ofFIGS. 6 and 7 is described with reference to implantedmedical device16 arranged withinpatient12, examples according to this disclosure also includelead29 connected transcutaneously to an external medical device that is configured to deliver electrical stimulation to the target nerve tissue, e.g.,vagus nerve150. Afterlead29 is placedadjacent vagus nerve150 and connected toIMD16,IMD16, either automatically or as partially or completely commanded byprogrammer24, may deliver electrical stimulation therapy to and/or receive sensor feedback fromvagus nerve150 throughelectrodes170.
• Intravascular lead placement proximate target nerve tissue within a patient generally requires minimally invasive surgical techniques because the medical leads used to deliver therapy are guided to the site through a blood vessel, e.g., a vein or artery that may be readily accessible, e.g., transcutaneously through a small incision. Intravascular lead placement techniques disclosed herein further facilitate placing the distal end of the lead in close proximity of the target nerve tissue, which can be arranged in different circumferential positions with respect to the blood vessel in which the lead is located.
• Intravascular techniques described in greater detail below may include structures and methods for deployment of one or more medical leads at a first location, testing stimulation at the first location, and, depending on the efficacy of the stimulation provided by electrodes on the leads at the first location, redeploying the leads to a second location. In one example, lead placement is improved by locating target nerve tissue with a sensor including, e.g., an IVUS imaging system and/or measuring the efficacy of test electrical stimulation pulses from an electrode on the lead through a blood vessel adjacent the target tissue. After a placement location is determined, one or more leads including one or more electrodes may be deployed into the vessel and anchored to a vessel wall near the target nerve tissue.
• FIGS. 9 and 10 illustrate examples of intravascular lead placement techniques in the context of vagal nerve stimulation in a human patient.FIG. 9 is a schematicillustration depicting lead29 intravascularly placedadjacent vagus nerve150 within internaljugular vein158 inpatient12. After or during placement, lead29 may be connected toIMD16 orINS26 similar to lead28 shown inFIGS. 1A and 1B respectively.FIG. 10 is a flow chart illustrating an example method of placinglead29 in accordance with the example ofFIG. 9. The example method ofFIG. 10 includes deploying a delivery catheter through a lumen of a blood vessel to a target nerve tissue site (240), identifying a location of the nerve tissue with respect to the blood vessel with one or more sensors connected to the delivery catheter (242), advancing an electrical stimulation electrode from the catheter within the blood vessel lumen toward the nerve tissue (244), energizing the electrode to deliver electrical stimulation from within the blood vessel lumen to the nerve tissue (246), comparing the efficacy of the nerve tissue stimulation to a threshold efficacy (248), and repositioning the delivery catheter and the electrode within the blood vessel lumen if the efficacy of the nerve tissue stimulation does not meet or exceed the threshold efficacy (250), or chronically deploying the electrode within the blood vessel lumen adjacent the nerve tissue if the efficacy of the nerve tissue stimulation meets or exceeds the threshold efficacy (252). One example of the method illustrated inFIG. 10 will be described in the context of the example lead placement structure shown inFIG. 9.
• The arrangement shown inFIG. 9 includesdelivery catheter220,sensor222, anddeployment member224.Sensor222 is connected tocatheter220 toward a distal end thereof.Deployment member224 is extendable and retractable fromcatheter220.Sensor222 is arranged between the distal end ofcatheter220 and the location alongcatheter220 from whichdeployment member224 is extendable and retractable.Deployment member224 includestubular member226, lead29,electrode228, andguidewire230.Guidewire230 includesanchor portion230A at a distal end thereof.Electrode228 is connected toward a distal end oflead29.Lead29 and guidewire230 are received within and advanceable through a lumen oftubular member226.Lead29 is advancable alongguidewire230.
• InFIG. 9,catheter220 is deployed through internaljugular vein158 ofpatient12 to a target nerve tissue stimulation site. In other examples,catheter220 may be deployed in other blood vessels withinpatient12 including, e.g.,carotid artery160, or the superior or inferior vena cava.Catheter220 can be any suitable delivery catheter capable of intravenous delivery withinpatient12 and adapted to accommodatesensor222 anddeployment member224.Sensor222 is connected to the distal end ofcatheter220 and is configured to detect the relative position ofvagus nerve150 outside ofjugular vein158, as well aselectrode228 onlead29 within the lumen ofvein158.Sensor222, in general, may be any suitable imaging or guidance system including, e.g., a fiberoptic endoscope, ultrasound imaging system, or any other on-board imaging system capable of assisting in the positioning ofcatheter220 andelectrode228 withinjugular vein158 relative tovagus nerve150 by providing an image of the area adjacent the location ofsensor222 oncatheter220. In some examples,sensor222 could be an array of receivers in relationship to a transmitter that provide an image of surrounding tissue and structures includingvagus nerve150 andelectrode228. In other examples,sensor222 may be configured to send or receive signals to or from any of a series of known signal generators including sonic, electromagnetic, light or radiation signals. In still other examples,sensor222 may be an optical oxygen content sensor that may be used to ensure thatlead29 andelectrode228 are not directed toward, e.g.,carotid artery160 during lead placement. In some examples,sensor222 may be employed in conjunction with one or more opaque markers viewable with fluoroscopic techniques or with an irrigated lumen that dispenses contrast media to assist in imaging the relative positions ofvagus nerve150 andelectrode228 onlead29 within the lumen ofjugular vein158.
• After the clinician identifies the location ofvagus nerve150 with respect tojugular vein158 based on the output ofsensor222, the clinician may advancedeployment member224 includingelectrode228 toward the wall of the lumen ofvein158 adjacent the nerve.Deployment member224, in general, is extendable and retractable fromcatheter220 from, e.g., an aperture formed in a sidewall thereof.Deployment member224 includestubular member226, lead29,electrode228, andguidewire230.Tubular member226 may be any structure including at least one lumen through which various electrode deployment structures including, e.g., lead29 and guidewire230 may be advanced to place an electrode withinvein158adjacent vagus nerve150. In the example ofFIG. 9,tubular member226 may be a needle with a lumen in which lead29 and guidewire230 are received and through which the same are advanceable.Electrode228 is connected to lead29, which is advanceable alongguidewire230.
• With the aid ofsensor222, the clinician advancesdeployment member224 fromcatheter220 towardvagus nerve150.Lead29, to whichelectrode228 is connected, and guidewire230 may be advanced through a lumen ofdeployment member224 to positionelectrode228 withinvein158adjacent vagus nerve150.Guidewire230 includesanchor portion230A at a distal end thereof that is configured to temporarily anchordeployment member224, lead29 andelectrode228, and guidewire230 to the wall of the lumen ofvein158. In the example ofFIG. 9,anchor portion230A ofguidewire230 is formed in a spiral that is configured to be twisted into the lumen wall.Anchor portion230A can be freed from the vessel wall by either untwistingguidewire230, or in the case that guidewire230 is sufficiently flexible, pulling the wire away from the spiralinganchor portion230A to effectively unwind and release the anchor from the wall ofjugular vein158. In addition toanchor portion230A ofguidewire230, lead29 includesbarbs231 that are configured to engage tissue ofjugular vein158 to anchorlead29 andelectrode228 to the wall of the vein afterguidewire230 has been retracted. In other examples, lead29 may be anchored to the wall ofvein158 with different structures including, e.g., a helical coil or other spiral coil shapes, C-shaped members, harpoon-like structures, hooks, expandable or serrated members, and the like. InFIG. 9,deployment member224 andelectrode228 onlead29 are advanced such that at least lead29 lies in the sensory field ofsensor222.
• In one example,sensor222 is an intravenous ultrasound (“IVUS”) imaging system that is adapted to radiate ultrasonic waves out fromsensor222 to generate a two dimensional image of the tissue andstructures surrounding catheter220 andsensor222.FIG. 11 is a schematic illustration of an example two dimensional ultrasonic image generated by a device coupled tosensor222 as arranged withcatheter220, lead29 andelectrode228 ofFIG. 9 located within thejugular vein158. When activated,sensor222 produces animaging field260 from ultrasonic waves produced by and radiating radially fromsensor222. The size ofimaging field260 may vary depending on the particular configuration and capabilities ofsensor222. The tissues and other structures caught withinimaging field260 ofsensor222 may be distinguished from one another and the relative positioning of the different structures may be discerned. In the example ofFIG. 11,vagus nerve150,jugular vein158, andcarotid artery160 are located withinimaging field260, whilecarotid sheath156 shown in shadow lines is not within the sensing range ofsensor222. By distinguishing different structures and displaying relative positions,sensor222 may be used to facilitatepositioning catheter220 andelectrode228 onlead29 withinjugular vein158 in a desired location relative tovagus nerve150 by, e.g., rotating the catheter and electrode within the blood vessel in the directions indicated byarrow262 inFIG. 11.
• Having deployedcatheter220, detected the location ofvagus nerve150 relative tojugular vein158, andadvanced electrode228 towardvagus nerve150, electrical stimulation may be delivered tovagus nerve150 through the wall of the lumen ofvein158 viaelectrode228. During test stimulation ofvagus nerve150, a portion oflead29 extending away from a distal end toward which electrode228 is arranged may be connected, e.g., transcutaneously to an external neurostimulation device that is configured to deliver electrical stimulation to the target nerve tissue, e.g.,vagus nerve150 whilelead29 andelectrode228 are being positioned relative thereto withinvein158. Afterlead29 is connected to the neurostimulator, the device, either automatically or as partially or completely commanded by a programmer, such asprogrammer24, may deliver electrical stimulation therapy to and/or receive sensor feedback fromvagus nerve150 throughelectrode228.
• In the example ofFIGS. 9 and 10, as well as other examples disclosed herein, the efficacy of the electrical stimulation delivered byelectrode228 tovagus nerve150 may be compared to a threshold efficacy to determine whether or not electrode228 is satisfactorily positioned with respect tonerve150. Efficacy refers, in general, to a combination of complete or partial alleviation of symptoms alone, or in combination with a degree of undesirable side effects. Efficacy may be measured, in general, by verbal feedback frompatient12, clinician observation of various conditions ofpatient12, or sensory feedback from one or more devices including, e.g.,ICD17 shown inFIG. 1A orcardiac therapy module104 shown inFIG. 4. Various physiological signals may be observed to measure the efficacy of the test stimulation, and thereby the need to repositionlead29relative vagus nerve150. For example, to determine the response to stimulation ofvagus nerve150, ECG, heart rate, blood pressure, blood flow, cardiac output, and/or breathing, ofpatient12 can be sensed or observed. These and other physiological signals may be detected in a variety of ways including sensing the signals using sense electrodes, pressure sensors, ultrasound sensors, motion sensors or other devices. In other examples, physiological reactions ofpatient12 may be observed or measured by, e.g., a clinician. In one example, efficacy may be measured by a sensor including, e.g., an accelerometer that determines if stimulation of the neck muscles or phrenic nerve ofpatient12 is occurring with or instead of stimulation ofvagus nerve150. In another example, a pressure sensor arranged coincident with or connected to lead29 may measure blood pressure by detecting the pressure withinjugular vein158. A pressure sensor, or other type of physiological feedback sensor, may also, in some examples, be connected tocatheter220 to measure, e.g., blood pressure withinvein158.
• In the event the nerve tissue stimulation meets or exceeds the threshold efficacy, lead29 andelectrode228 may be chronically deployed withinjugular vein158adjacent vagus nerve150. On the other hand, if the nerve stimulation delivered byelectrode228 does not provide the threshold level of efficacy in relieving the symptoms ofpatient12,catheter220 andelectrode228 may be repositioned withinjugular vein158 to improve the location of the components, inparticular electrode228 with respect tovagus nerve150. Generally speaking,catheter220 andelectrode228 may be repositioned by rotatingcatheter220 withinjugular vein158 in the manner described with reference toFIG. 11 and with the assistance of, e.g., ultrasound imaging provided bysensor222. In some examples, guidewire230 includinganchor portion230A may be retracted along withlead29 andelectrode228 intodeployment member224 before repositioningcatheter220 and then redeployed after the catheter has be relocated. After repositioningcatheter220 andelectrode228, the process of stimulatingvagus nerve150 and comparing the efficacy of the nerve stimulation to a threshold efficacy may be repeated until the arrangement ofelectrode228 with respect tovagus nerve150 delivers electrical stimulation therapy that meets or exceeds the threshold efficacy level.
• After determining a placement location that delivers satisfactory treatment efficacy, lead29 andelectrode228 may be chronically deployed withinjugular vein158adjacent vagus nerve150. After chronic deployment oflead29 andelectrode228, a portion oflead29 extending away from a distal end toward which electrode228 is arranged may be guided to connect with, e.g.,IMD16. In one example, lead29 may be guided intravascularly to an implantation location ofIMD16 withinpatient12. In other examples, lead29 may be tunneled through tissue ofpatient12 to be connected toIMD16. Afterlead29 is placedadjacent vagus nerve150 and connected toIMD16,IMD16, either automatically or as partially or completely commanded byprogrammer24, may deliver electrical stimulation therapy to and/or receive sensor feedback fromvagus nerve150 throughelectrode228.
• FIGS. 12A and 12B show alternative examples ofdeployment member224 for use in methods and systems according to this disclosure. In general,FIGS. 12A and 12B show different arrangements and combinations of anchoring members and electrodes with respect totubular member226, lead29, and guidewire230 ofdeployment member224. In the interest of simplicity,catheter220 has been omitted from the illustrations ofFIGS. 12A and 12B. InFIG. 12A,deployment member224 is arranged withinjugular vein158adjacent vagus nerve150 and includestubular member226, lead29,electrode228, guidewire230, andexpandable member270. In some examples,expandable member270 may provide additional stabilization or biasing oflead29 or other components ofdeployment member224 withinjugular vein158. For example,expandable member270 may push against catheter220 (not shown inFIG. 12A) to bias lead29 andelectrode228 toward the wall of the lumen ofvein158. In another example,expandable member270 may further stabilize the placement oflead29 andelectrode228 by expanding to apply force on the lumen wall andcatheter220. Theexpandable member270 may, in some examples, be a balloon catheter including, e.g., an angioplasty catheter. In other examples,expandable member270 may be a stent or deployable spline or lobe.
• FIG. 12B showsdeployment member224 withadditional electrode272 connected totubular member226. InFIG. 12B,deployment member224 is arranged withinjugular vein158adjacent vagus nerve150 and includestubular member226, lead29,electrode228, guidewire230, andelectrode272. Although intravascular placement examples oflead29 have been described herein with reference to asingle electrode228 for simplicity, in practice, lead29 will commonly include a plurality of electrodes that may be employed in different anode and cathode combinations to stimulatevagus nerve150 as, e.g., described with reference to electrodes80-83 inFIG. 2. Additionally and as illustrated inFIG. 12B,deployment member224 may include electrodes in addition tolead electrode228 arranged in different locations and/or connected to different components.Electrode272 is connected totubular member226 in the example ofFIG. 12B. In some examples,tubular member226 andelectrode272 may be advanced towardvagus nerve150 prior to chronically deployinglead29 andelectrode228. In such examples,electrode272 may be used to deliver test stimulation pulses tovagus nerve150 to determine the efficacy of the placement ofdeployment member224 withinjugular vein158 with respect tovagus nerve150. After determining a position of deployment member that provides a threshold efficacy in stimulatingvagus nerve150, lead29 and guidewire230 may be advanced throughtubular member226 and lead29 andelectrode228 may be chronically deployed along the wall of the lumen ofjugular vein158adjacent vagus nerve150.
• In addition to placinglead29 andelectrode228 intravascularly usingdeployment member224 as shown in the examples ofFIGS. 9,11,12A and12B, lead29 andelectrode228 may be advanced from a distal tip ofcatheter220 to be actively fixed to the wall ofjugular vein158 as shown inFIG. 13. The arrangement shown inFIG. 13 includesdelivery catheter220,sensor222, lead29,electrodes228 and229, andactive fixation member274.Sensor222 andelectrode229 are connected tocatheter220 toward a distal end thereof.Electrode228 is connected toward a distal end oflead29.Lead29 andelectrode228 are received within and advanceable through a lumen ofcatheter220 and out of the tip of the catheter to placeelectrode228 withinvein158adjacent vagus nerve150. Although not shown inFIG. 13, lead29 may be advanced along and guided by a guide member including, e.g., a guidewire or a stylus.
• InFIG. 13,catheter220 is deployed through internaljugular vein158 ofpatient12 to a target nerve tissue stimulation site. In other examples,catheter220 may be deployed in other blood vessels withinpatient12 including, e.g.,carotid artery160, or the superior or inferior vena cava.Catheter220 can be any suitable delivery catheter capable of intravenous delivery withinpatient12 and adapted to accommodatesensor222,electrode229, and lead29. In some examples,catheter220 may be flexible or curved to direct the tip of the catheter laterally toward the wall ofjugular vein158.Sensor222 is connected to the distal end ofcatheter220 and is configured to detect the relative position ofvagus nerve150 outside ofjugular vein158.Sensor222, in general, may be any suitable imaging or guidance system including, e.g., a fiberoptic endoscope, ultrasound imaging system, or any other on-board guidance or imaging system capable of assisting in the positioning ofcatheter220 withinjugular vein158 relative tovagus nerve150 by providing an image of the area adjacent the location ofsensor222 oncatheter220.
• Electrode229 is also connected to a distal end ofcatheter220 and may be advanced toward the wall of the lumen ofjugular vein158 to deliver test stimulation pulses tovagus nerve150 through the wall ofvein158.Electrode229 may therefore be employed in addition to or in lieu ofsensor222 to detect the relative position ofvagus nerve150 outside ofjugular vein158. During test stimulation ofvagus nerve150,electrode229 may be connected to a conductor connected, e.g., transcutaneously to an external neurostimulation device that is configured to deliver electrical stimulation to the target nerve tissue, e.g.,vagus nerve150. Afterelectrode229 is connected to the neurostimulator, the device, either automatically or as partially or completely commanded by a programmer, such asprogrammer24, may deliver electrical stimulation therapy to and/or receive sensor feedback fromvagus nerve150.
• In the example ofFIG. 13, as well as other examples disclosed herein, the efficacy of the electrical stimulation delivered byelectrode229 tovagus nerve150 may be compared to a threshold efficacy to determine whether or not electrode229, and therebycatheter220 is satisfactorily positioned with respect tonerve150. Efficacy may be measured, in general, by verbal feedback frompatient12, clinician observation of various conditions ofpatient12, or sensory feedback from one or more devices including, e.g.,ICD17 shown inFIG. 1A orcardiac therapy module104 shown inFIG. 4. Various physiological signals may be observed to measure the efficacy of the test stimulation, and thereby the need to repositioncatheter220 andelectrode229relative vagus nerve150. For example, to determine the response to stimulation ofvagus nerve150, ECG, heart rate, blood pressure, blood flow, cardiac output, and/or breathing, ofpatient12 can be sensed or observed. These and other physiological signals may be detected in a variety of ways including sensing the signals using sense electrodes, pressure sensors, ultrasound sensors, motion sensors or other devices. In other examples, physiological reactions ofpatient12 may be observed or measured by, e.g., a clinician. In one example, efficacy may be measured by a sensor including, e.g., an accelerometer that determines if stimulation of the neck muscles or phrenic nerve ofpatient12 is occurring with or instead of stimulation ofvagus nerve150. In another example, a pressure sensor arranged coincident with or connected tocatheter220 may measure blood pressure by detecting the pressure withinjugular vein158.
• In the event the nerve tissue stimulation meets or exceeds the threshold efficacy, lead29 andelectrode228 may be chronically deployed by advancing the lead from the tip ofcatheter220 withinjugular vein158 towardvagus nerve150. On the other hand, if the nerve stimulation delivered byelectrode229 does not provide the threshold level of efficacy in relieving the symptoms ofpatient12,catheter220 andelectrode229 may be repositioned withinjugular vein158 to improve location with respect tovagus nerve150. Generally speaking,catheter220 andelectrode229 may be repositioned by rotatingcatheter220 withinjugular vein158 to different incremental positions until an acceptable position forcatheter220 relative tovagus nerve150 is determined. After repositioningcatheter220 andelectrode229, the process of stimulatingvagus nerve150 and comparing the efficacy of the nerve stimulation to a threshold efficacy may be repeated until the arrangement ofcatheter220 with respect tovagus nerve150 delivers electrical stimulation therapy that meets or exceeds the threshold efficacy level.
• Oncecatheter220 is positioned withinjugular vein158 such thatelectrode229 delivers stimulation that meets or exceeds the threshold efficacy, lead29 andelectrode228 may be advanced through a lumen ofcatheter220 and out of the tip of the catheter to actively fixlead29 andelectrode228 to the wall ofvein158adjacent vagus nerve150. InFIG. 13,catheter220 is curved to direct the tip of the catheter laterally toward the wall ofjugular vein158. Connected to a distal end oflead29 isactive fixation member274, which, in the example ofFIG. 13 is a helical coil that is configured to be twisted into the wall ofjugular vein158.
• In practice, lead29,electrode228, andfixation member274 may be advanced laterally from the tip ofcatheter220 toward the wall ofjugular vein158adjacent vagus nerve150. In some examples, lead29 may be directed toward the wall ofvein158 along a trajectory that is approximately perpendicular to the wall.Active fixation member274 engages the wall of the lumen ofjugular vein158 by, e.g., twistinglead29 to screw the helical fixation member into the wall. After actively fixinglead29 andelectrode228 to the wall ofvein158adjacent vagus nerve150,catheter220 may be removed, after which lead29 andelectrode228 will lay down along and approximately tangential to the wall ofvein158.
• In some examples,active fixation member274 may be electrically active such that it acts as an electrode in addition to or in lieu ofelectrode228.Fixation member274 may have a variety of lengths and helical pitches. In some examples,fixation member274 may have a length in the range from and including approximately 0.5 millimeters to and including approximately 2.5 millimeters. In other examples,fixation member274 may have a length in the range from and including approximately 1 millimeters to and including approximately 2 millimeters. The pitch of the helical coil ofactive fixation member274 may also vary in different examples according to this disclosure. In general, in examples in whichfixation member274 is electrically active, it may be desirable to increase the pitch to increase the amount of surface area engaging tissue of the wall ofjugular vein158. In some examples,fixation member274 may have a helical pitch in the range from and including approximately 0.5842 millimeters to and including approximately 1.016 millimeters.
• FIGS. 14A-14J are elevation front views of various anchors that may be used alone or in combination to anchor or bias a medical lead and/or electrode within a vessel in accordance with examples disclosed herein. The anchors illustrated inFIGS. 14A-14J may be employed, for example, in a manner as described with reference to anchorportion230A ofguidewire230 and/orbarbs231 inFIG. 9. In such examples,anchor portion230A ofguidewire230 and/orbarbs231 may take an alternative form to that shown inFIG. 9 including, e.g., the harpoon shapes ofFIGS. 14B and 14C. In another example, a portion oflead29 may be shaped as shown inFIG. 14A,14D, or14F and wedged intojugular vein158 to anchor the lead andelectrode228 within the veinadjacent vagus nerve150.
• In addition to the intravascular techniques described with reference toFIGS. 9-14, examples according to this disclosure also include techniques employing an expandable and contractible generally cylindrical lead member that is temporarily deployable for testing multiple electrode orientations and combinations before deploying the member for chronic stimulation of target nerve tissue within a patient.
• FIGS. 15 and 16 illustrate examples of intravascular lead placement techniques including a generally cylindrical expandable and contractible lead member in the context of vagal nerve stimulation in a human patient.FIG. 15 is a schematicillustration depicting lead29 attached tocylindrical lead member300, both of which are intravascularly placedadjacent vagus nerve150 within internaljugular vein158 inpatient12. After or during placement, lead29 andlead member300 may be connected toIMD16 orINS26 similar to lead28 shown inFIGS. 1A and 1B respectively.FIG. 16 is a flow chart illustrating an example method of placinglead29 andcylindrical lead member300 in accordance with the example ofFIG. 15. The example method ofFIG. 16 includes arranging a generally cylindrical expandable and contractible lead member within a lumen of a blood vessel adjacent target nerve tissue (310), temporarily deploying the cylindrical lead member within the lumen relative to the nerve tissue (312), energizing one or more electrodes connected to the cylindrical lead member to deliver electrical stimulation from within the blood vessel lumen to the nerve tissue (314), comparing the efficacy of the nerve tissue stimulation to a threshold efficacy (316), and redeploying the cylindrical lead member within the lumen relative to the nerve tissue if the efficacy of the nerve tissue stimulation does not meet or exceed the threshold efficacy (318), or chronically deploying the cylindrical lead member in an expanded state within the lumen if the efficacy of the nerve tissue stimulation meets or exceeds the threshold efficacy (320). One example of the method illustrated inFIG. 16 will be described in the context of the example lead structure shown inFIG. 15.
• The arrangement shown inFIG. 15 includeslead member28,cylindrical lead member300, andelectrodes302. As will be described in greater detail below, some examples may include additional components for arranging and deployingcylindrical lead member300 within a blood vessel including, e.g., a delivery catheter and/or a stylus or other active deployment mechanism. Cylindricallead member300 is connected to a distal end oflead member28.Electrodes302 are connected to an exterior surface oflead member300 and are arranged incolumns304 parallel to a longitudinal axis oflead member300. Depending on howelectrodes302 are grouped, they may also be seen inFIG. 15 as arranged incolumns306 that wrap around the exterior surface oflead member300 oriented at an angle with respect to the longitudinal axis of the cylindrical lead member. In other examples according to this disclosure,lead member300 may include fewer ormore electrodes302 than shown in the example ofFIG. 15. For example,lead member302 may include more than twocolumns306 ofelectrodes302 distributed circumferentially around the exterior surface ofcylindrical lead member300. Cylindricallead member300 is an expandable and retractable component that may be deployed and redeployed passively or actively within a blood vessel.Lead member300 is shown schematically inFIG. 15 in a contracted state in dashed lines and in an expanded state in solid lines. As described in greater detail below,cylindrical lead member300 may be any one of a number of different structures that are capable of active and/or passive deployment and redeployment including, e.g., circular cylindrical members, wire mesh stents, and spiral wire and ribbon members.
• InFIG. 15, lead29 andcylindrical lead member300 are arranged within the lumen of internaljugular vein158adjacent vagus nerve150. In other examples,lead member300 may be deployed in other blood vessels withinpatient12 including, e.g.,carotid artery160adjacent vagus nerve150 or another vein or artery adjacent the target nerve tissue at which stimulation therapy is directed. Cylindricallead member300 may be guided to the target nerve tissue site withinpatient12 by, e.g., a small transcutaneous incision to gain access tojugular vein158 and then directed through the vein by, e.g., a delivery catheter to the target siteadjacent vagus nerve150.
• After arrangingcylindrical lead member300 within the lumen ofjugular vein158adjacent vagus nerve150,lead member300 may be temporarily deployed within the lumen relative tovagus nerve150.Vagus nerve150 is positioned withinpatient12 outside ofjugular vein158, which has a generally tubular shape. Upon intravascular implantation oflead member300 withinjugular vein158, the relative orientation ofvagus nerve150 around the periphery ofjugular vein158 may not be known without, e.g., complete dissection ofcarotid sheath156. Deployment oflead member300 withinjugular vein158 and stimulation ofvagus nerve150 by selected ones ofelectrodes302 may initially be somewhat arbitrary with respect to the actual position ofvagus nerve150 without testing or feedback regarding the orientation and combination ofelectrodes302 used. Therefore,cylindrical lead member300 is capable of deployment and redeployment withinjugular vein158adjacent vagus nerve150 to test multiple orientations and combinations ofelectrodes302 before deploying the lead member for chronic treatment ofpatient12.
• As indicated inFIG. 15 byarrow308,lead member300 is capable of being rotated withinjugular vein158 to vary the orientation oflead member300, and therebyelectrodes302 within the vein.Lead member300 may be oriented withinjugular vein158 both by rotating the lead member and also may be, in some examples, temporarily expanded to abut the walls of the lumen ofvein158 as shown inFIG. 15. In addition to orienting and expandinglead member300,electrodes302 may be selectively activated in different combinations in a manner similar to that described with reference toFIG. 2. For example, lead29 andcylindrical lead member300 may be connected toIMD16 shown inFIGS. 1A and 2.Neurostimulation therapy module106 ofIMD16 may include a switching module to selectively couple pairs ofelectrodes302 to signalgenerator112 and/orsensing module114 to form different anode-cathode combinations. The switching module may include, e.g., a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple stimulation energy to selected electrodes. In one example, the switching module may select combinations ofelectrodes302 grouped alonglongitudinal column304 inFIG. 15. In another example, however, the switching module may select combinations ofelectrodes302 grouped along the skewedcolumns306. In this manner, deployinglead member300 within the lumen ofjugular vein158 may include both orienting and expandinglead member300 andelectrodes302 within the vein, and selecting combinations ofelectrodes302 to stimulate (and/or sense nerve signals from)vagus nerve150. During the placement oflead member300, lead29 may be transcutaneously connected toIMD16 to test the placement oflead member300 prior to implanting the device withinpatient12. In another example, lead29 may be connected to an external neurostimulation device that is configured to deliver electrical stimulation tovagus nerve150 whilelead member300 is being positioned relative thereto withinvein158.
• Aftercylindrical lead member300 andelectrodes302 have been temporarily deployed withinjugular vein158, one or more of the electrodes may be energized to deliver electrical stimulation tovagus nerve150. During test stimulation ofvagus nerve150, a portion oflead29 extending away from a distal end to whichlead member300 andelectrodes302 may be connected, e.g., transcutaneously to an external neurostimulation device that is configured to deliver electrical stimulation to the target nerve tissue, e.g.,vagus nerve150 whilelead member300 andelectrodes302 are being positioned relative thereto withinvein158. Aftercylindrical lead member300 is placedadjacent vagus nerve150 and connected to the external neurostimulator, the device, either automatically or as partially or completely commanded by a programmer, such asprogrammer24, may deliver electrical stimulation therapy to and/or receive sensor feedback fromvagus nerve150 through one or more ofelectrodes302.
• In the example ofFIGS. 14 and 15, as well as other examples disclosed herein, the efficacy of the electrical stimulation delivered byelectrodes302 tovagus nerve150 may be compared to a threshold efficacy to determine whether or not cylindricallead member300 andelectrodes302 are satisfactorily positioned with respect tonerve150 and/or an optimal combination ofelectrodes302 has been selected to deliver stimulation to the nerve. As described above with reference toFIGS. 9 and 10, efficacy may be measured, in general, by verbal feedback frompatient12, clinician observation of various conditions ofpatient12, or sensory feedback from one or more sensors. Various physiological signals may be observed to measure the efficacy of the test stimulation, and thereby the need to repositionlead member300relative vagus nerve150. For example, to determine the response to stimulation ofvagus nerve150, ECG, heart rate, blood pressure, blood flow, cardiac output, and/or breathing, ofpatient12 can be sensed or observed.
• In the event the nerve tissue stimulation meets or exceeds the threshold efficacy,cylindrical lead member300, to whichelectrodes302 are attached, may be chronically deployed in an expanded state withinjugular vein158adjacent vagus nerve150. The orientation ofcylindrical lead member300 and selected combination ofelectrodes302 that delivered therapy topatient12 meeting or exceeding the threshold efficacy may be used to deliver chronic, i.e. long term therapy to the patient. On the other hand, if the nerve stimulation delivered bycylindrical lead member300 andelectrodes302 does not provide the threshold level of efficacy in treatingpatient12,lead member300 may be redeployed withinjugular vein158 relative tovagus nerve150. As with the initial temporary deployment, redeployinglead member300 may include orienting the lead member by rotating withinjugular vein158, as well as selecting one or more combinations ofelectrodes302 to stimulatevagus nerve150. In some examples of redeployment,lead member300 may also be contracted and then re-expanded to abut the walls of the lumen ofjugular vein158 as shown inFIG. 15. For example, in theevent lead member300 was previous expanded withinjugular vein158, the lead member may need to be contracted in order to be reoriented by rotating it within the vein. After redeployingcylindrical lead member300, the process of stimulatingvagus nerve150 and comparing the efficacy of the nerve stimulation to a threshold efficacy may be repeated until the arrangement oflead member300 with respect tovagus nerve150 delivers electrical stimulation therapy that meets or exceeds the threshold efficacy level.
• After determining a placement location that delivers satisfactory treatment efficacy,cylindrical lead member300, to whichelectrodes302 are attached, may be chronically deployed in an expanded state withinjugular vein158adjacent vagus nerve150. After chronic deployemnet oflead member300, a portion oflead29 extending away from a distal end toward which leadmember300 is arranged may be guided to connect with, e.g.,IMD16. In one example, lead29 may be guided intravascularly to an implantation location ofIMD16 withinpatient12. In other examples, lead29 may be tunneled through tissue ofpatient12 to be connected toIMD16. Afterlead29 is placedadjacent vagus nerve150 and connected toIMD16,IMD16, either automatically or as partially or completely commanded byprogrammer24, may deliver electrical stimulation therapy to and/or receive sensor feedback fromvagus nerve150 throughelectrodes302.
• FIGS. 17A and 17B, and18A-18D show several examples ofcylindrical lead member300 and delivery mechanisms appropriate for use in the example ofFIGS. 15 and 15.FIGS. 17A and 17B are schematic illustrations of a cylindrical lead member arranged within a delivery catheter for deploying and redeploying the lead member withinjugular vein158 relative tovagus nerve150.FIGS. 18A-18D are schematic illustrations of different examples of a cylindrical lead member that is expandable and contractible for deployment and redeployment withinvein158.
• Generally speaking, there are several methods by whichcylindrical lead member300 may be temporarily and then chronically deployed within a blood vessel to test various orientations and combinations ofelectrodes302 relative tovagus nerve150. In some examples,cylindrical lead member300 may be arrangedadjacent vagus nerve150 within a delivery mechanism that allows for the flexible orientation and selection of combinations ofelectrodes302 withinjugular vein150 relative to the position ofvagus nerve150. For example,lead member300 may be arranged within a delivery catheter that accommodates relative movement of the lead member and the catheter to expose different combinations ofelectrodes302 oriented in different positions withinvein158 relative tovagus nerve150. In other examples,cylindrical lead member300 may be actively expandable and contractible such that the lead member may be expanded withinjugular vein158 and thereafter contracted and re-expanded in a different orientation relative tovagus nerve150.
• FIGS. 17A and 17B are schematic illustrations of a cylindrical lead member arranged within a delivery catheter that accommodates relative movement of the lead member and the catheter to expose different combinations ofelectrodes302 oriented in different positions withinvein158 relative tovagus nerve150. InFIG. 17A, lead29 andcylindrical lead member300 connected thereto are arranged withindelivery catheter330.Electrodes302 are connected to leadmember300 and arranged incolumns304 that are generally parallel to a longitudinal axis of the lead member.Catheter330 includes a plurality ofapertures332 that are shaped and sized to expose groups ofelectrodes302. In the example ofFIG. 17A,apertures332 are generally rectangular slots incatheter330. However, in other example,apertures332 may be, e.g., holes arranged to expose one or more ofelectrodes302.
• In practice,delivery catheter330 andlead member300 may be guided intravascularly to a target tissue site throughjugular vein158adjacent vagus nerve150. Cylindricallead member300 may be oriented withincatheter330 such that select groups ofelectrodes302 are exposed byapertures332. In the example ofFIG. 17A,electrodes302 will be generally exposed in groups arranged alonglongitudinal columns304. However, in other examples,apertures332 may be shaped and oriented to expose one ormore electrodes302 in different groups including, e.g., groups arranged along columns oriented at an angle with respect to a longitudinal axis oflead member300, such ascolumns306 shown inFIG. 15. In any event, afterlead member300 andelectrodes302 are oriented withincatheter330, different combinations ofelectrodes302 may deliver electrical stimulation tovagus nerve150. Cylindricallead member300 and/orcatheter330 may be reoriented withinjugular vein158 one or more times to test different orientations and combinations ofelectrodes302 until a threshold efficacy is indicated. Thereafter,cylindrical lead member300 andelectrodes302 may be chronically deployed in an expanded state by, e.g., withdrawingdelivery catheter330 to allowlead member300 to passively expand to abut the walls of the lumen ofjugular vein158.
• InFIG. 17B,cylindrical lead member340 is arranged withindelivery catheter342.Electrodes344 are connected to leadmember340.Electrodes344 are ring electrodes arranged around the exterior surface of and distributed longitudinally alonglead member340.Catheter342 includeshelical aperture346 that is shaped and sized to expose portions of each ofelectrodes340 at different rotational orientations within a blood vessel. In the example ofFIG. 17A,apertures346 is a generally rectangular slot incatheter342. However, in other examples,catheter342 may include a series of holes arranged in a helical line to expose different portions ofelectrodes344 oriented at different rotational positions.
• Similar to the example ofFIG. 17A,delivery catheter342 andlead member340 may be guided intravascularly to a target tissue site throughjugular vein158adjacent vagus nerve150. Cylindricallead member340 may be oriented withincatheter342 such that select portions ofelectrodes344 are exposed at different rotational orientations with respect tovagus nerve150. Afterlead member340 andelectrodes344 are oriented withincatheter346, different combinations ofelectrodes344 may deliver electrical stimulation tovagus nerve150.Catheter346 may then be rotated relative to leadmember340 withinjugular vein158 one or more times to test different orientations and combinations ofelectrodes344 until a threshold efficacy is indicated.
• The catheters shown inFIGS. 17A and 17B may, in some examples, act as permanent components deployed along with cylindrical lead members, instead of temporary delivery components that are used to arrange and deploy the lead members and are thereafter removed. For example, the catheters and the cylindrical lead members may be arranged within a blood vessel such that the catheter abuts and thereby is fixed within the lumen of the blood vessel. In such examples, the cylindrical lead member may be rotated within the catheter to vary electrode orientation and combinations. The lead member may remain in an expanded state abutting a lumen of the catheter from initial implantation until chronic deployment, or, in other examples, may contract to be reoriented and expand to test the new electrode orientation and/or combination. In any event, the catheters may remain deployed along with the cylindrical lead members within the blood vessel for chronic treatment of a patient.
• FIGS. 18A-18D are schematic illustrations of different examples of a cylindrical lead member that is expandable and contractible for deployment and redeployment withinjugular vein158 ofpatient12.FIGS. 18A and 18B show meshstent lead member350 with different electrode configurations, whileFIGS. 18C and 18D show two different helicallead members352 and354 respectively. InFIGS. 18A and 18B, meshstent lead member350 includes a plurality ofmaterial segments356 each of which is pivotally joined at either end to another segment at a vertex.Material segments356 may be constructed from various biocompatible materials that resists corrosion and degradation from bodily fluids including, e.g., titanium or biologically inert polymers. Generally speaking, meshstent lead member350 is expandable and contractible by rotation ofmaterial segments356 with respect to each other at the plurality of vertices at which the segments are pivotally joined. As meshstent lead member350 contracts,material segments356 rotate such that the angle of each segment with respect to a longitudinal axis oflead member350 decreases, which in turn decreases the diameter and increases the overall length of the lead member. Conversely, as meshstent lead member350 expands,material segments356 rotate such that the angle of each segment with respect to the longitudinal axis oflead member350 increases, which in turn increases the diameter and decreases the overall length of the lead member. Other examples according to this disclosure may include stent lead members having different configurations thanlead member350 ofFIGS. 18A and 18B. For example, in one example, a mesh stent member may include fewer or more material segments pivotally joined at fewer or more vertices to form coarser or finer meshes than meshstent lead member350. In another example, a stent lead member may be constructed from a polymer that is expandable to take the shape of the blood vessel in which it is arranged. In still another example, a mesh stent member may include a resorbable material interconnecting some or all of the mesh that would, over a period of time leave only the mesh of material segments and electrodes within the blood vessel of the patient.
• FIGS. 18A and 18B illustratestent lead member350 with different electrode configurations. InFIG. 18A,electrodes302 are connected to leadmember350 substantially coincident with the vertices at whichmaterial segments356 are joined. In other examples, only some of the junctions betweenmaterial segments356 may includeelectrodes302 arranged thereon or about.Electrodes302, as illustrated inFIG. 18A, may protrude from the exterior surface oflead member350, or any other cylindrical lead member according to this disclosure. In this manner,electrodes302 may penetrate the wall of the blood vessel lumen in which leadmember350 is arranged, e.g.jugular vein158, to assist in fixing the lead member within the vessel. InFIG. 18B, on the other hand, lead29 is wrapped partially or completely aroundstent lead member350 and includesring electrodes358 attached thereto. Wrappinglead29 aroundlead member350 along a helical trajectory as shown inFIG. 18B may provide a mechanical advantage for expansion of the lead member, because, in such an orientation, lead29 may not need to stretch as the overall length oflead member350 increases.
• FIGS. 18C and 18D show two different helicallead members352 and354 respectively.Lead member352 is a helical wire, whilelead member354 is a helical ribbon. Both wire and ribbonhelical lead members352 and354 includeelectrodes302 electrically connected to lead29 and arranged generally in one or more lines parallel to the helical trajectory of each lead member. Generally speaking,helical lead members352 and354 are expandable and contractible by bringing theirrespective ends352A,352B and354A,354B closer together or further apart. In the case of helicalwire lead member352, as ends352A and352B are brought closer together, individual windings of the helical wire are also brought closer together and the diameter of the helix oflead member352 expands. Conversely, as ends352A and352B are brought further apart, individual windings of the helical wire are also brought further apart and the diameter of the helix oflead member352 contracts. In the case of helicalribbon lead member354, as ends354A and354B are brought closer together,helical slot360 closes and the diameter of the helix oflead member354 expands. Conversely, as ends354A and354B are brought further apart,helical slot360 is opened and the diameter of the helix oflead member354 contracts.
• Cylindrical lead members employed in examples according to this disclosure, in general, may include several additional features. In some examples, a lead member may include a non-conductive material that insulates non-targeted tissue from stimulation pulses delivered by one or more electrodes connected to the lead member or otherwise isolates one or more electrodes from, e.g., other parts of the lead member. In addition to employing electrodes that protrude from the exterior surface of a cylindrical lead member to assist in fixation within a vessel (see, e.g.,FIG. 18A), the lead member may include an abrasive or otherwise coarse exterior surface or a drug-eluting coating that promotes tissue growth around the lead member, e.g. promotes fibrosis. Conversely, in other examples, a cylindrical lead member according to this disclosure may include a drug-eluting coating that inhibits tissue growth, such as fibrosis to, e.g., increase the long term period over which the cylindrical member may be redeployed within a blood vessel. Additionally, in some examples, a cylindrical lead member may include a drug-eluting coating that prevents or inhibits stenosis of the blood vessel in which it is arranged. In other examples, the cylindrical lead member may include a number microhooks or small barbs arranged on an exterior surface to hold the lead member in place within the blood vessel.
• Cylindrical lead members according to this disclosure may also be deployed and redeployed with the assistance of, e.g. a cup and release plate that receive one end of the lead member and serve to retain the lead member in place when, e.g., a sheath is retracted to temporarily or chronically deploy the lead member in a blood vessel. In some examples, the cup may be relatively deep to encapsulate a large longitudinal length of a proximal end of the lead member that is configured to expand to deploy the lead member. The cup may hold and encapsulate the proximal end of the lead member while a sheath extends over and encapsulates the lead member and the cup prior to deployment and after the sheath is retracted. After the sheath is retracted to partially deploy the lead member, e.g., allow the distal end to expand in the blood vessel, the sheath may then either be extended again to redeploy the cylindrical lead member, or the release plate may be extended to push out and thereby release and deploy the proximal end of the cylindrical member from the cup. Other examples and a more detailed explanation of deployment mechanisms including such cup arrangements are described in U.S. Patent Publication No. 2007/0043420 A1 to Timothy W. Lostetter, filed on Aug. 17, 2005 and entitled “APPARATUS AND METHOD FOR STENT-GRAFT RELEASE USING A CAP,” the entire content of which is incorporated herein by this reference.
• In some examples, a cylindrical lead member may include an electrical stimulator and, in some cases, need not be coupled to an implantable medical device via a lead. In such examples, the electrical stimulator on, within or attached to the cylindrical lead member may be powered by radio frequency pulses delivered from either an external or a subcutaneously implanted RF transmitter to a receiver unit arranged with the stimulator or cylindrical lead member. In other examples, some part of the stimulator or cylindrical lead member may be composed of a piezoelectric material that can generate current when excited mechanically by ultra sound waves transmitted from an external or implanted source.
• Similar to intravascular techniques, transvascular lead placement proximate a target nerve tissue site generally requires minimally invasive surgical techniques because the leads are guided to the site through a blood vessel, e.g., a vein or artery that may be readily accessible, e.g., transcutaneously through a small incision. Unlike intravascular, however, transvacular techniques guide the lead adjacent the target tissue site and then pierce the vessel wall to arrange the lead and electrodes outside of the vessel adjacent the nerve tissue at which therapy is directed. Transvascular lead placement techniques according to this disclosure provide for lead placement relative to the target nerve tissue and neighboring blood vessels to improve the therapeutic effects of electrical stimulation provided to the patient by lead electrodes. Additionally, guided transvascular lead placement as described herein may avoid safety risks of such procedures including, e.g., piercing adjacent vessels, such as an artery. The disclosed transvascular techniques generally include improving lead placement by locating target nerve tissue with a sensor, such as an IVUS imaging system, through a blood vessel adjacent the target tissue. After a placement location is determined, one or more leads including one or more electrodes may be deployed through the vessel wall and anchored to the vessel wall or other tissue near the target nerve tissue.
• Transvascular techniques generally include improving lead placement by locating target nerve tissue with a sensor including, e.g., an IVUS imaging system through a blood vessel adjacent the target tissue. After an optimal placement location is determined relative to the nerve tissue with the assistance of the tissue sensor, one or more leads including one or more electrodes may be deployed through the vessel wall and anchored to the vessel wall or other tissue near the target nerve tissue.
• FIGS. 18 and 19 illustrate examples of transvascular lead placement techniques in the context of vagal nerve stimulation in a human patient.FIG. 19 is a schematicillustration depicting lead29 transvascularly placedadjacent vagus nerve150 outside of internaljugular vein158 inpatient12. After or during placement, lead29 may be connected toIMD16 orINS26 similar to lead28 shown inFIGS. 1A and 1B respectively.FIG. 20 is a flow chart illustrating an example method of placinglead29 in accordance with the example ofFIG. 19. The example method ofFIG. 20 includes deploying a delivery catheter through a lumen of a blood vessel to a target nerve tissue site (380), identifying a location of the nerve tissue with respect to the blood vessel with one or more sensors connected to the delivery catheter (382), advancing an electrical stimulation electrode from the catheter through a wall of the blood vessel toward the nerve tissue (384), and energizing the electrode to deliver electrical stimulation to the nerve tissue (386). One example of the method illustrated inFIG. 20 will be described in the context of the example lead placement structure shown inFIG. 19.
• The arrangement shown inFIG. 19 includesdelivery catheter220,sensor222,deployment member224, andspline370.Sensor222 is connected tocatheter220 toward a distal end thereof.Deployment member224 is extendable and retractable fromcatheter220.Spline370 is also connected to a distal end ofcatheter220 and is deployable to stabilize the catheter withinjugular vein158.Sensor222 is arranged between the distal end ofcatheter220 and the location alongcatheter220 from whichdeployment member224 is extendable and retractable.Deployment member224 includestubular member226, lead29,electrode228, andguidewire230.Guidewire230 includesanchor portion230A at a distal end thereof.Electrode228 is connected toward a distal end oflead29.Lead29 and guidewire230 are received within and advanceable through a lumen oftubular member226.Lead29 is advancable alongguidewire230.
• InFIG. 19,catheter220 is deployed through internaljugular vein158 ofpatient12 to a target nerve tissue stimulation site. In other examples,catheter220 may be deployed in other blood vessels withinpatient12 including, e.g.,carotid artery160, or the superior or inferior vena cava.Catheter220 can be any suitable delivery catheter capable of intravenous delivery withinpatient12 and adapted to accommodatesensor222 anddeployment member224.Sensor222 is connected to the distal end ofcatheter220 and is configured to detect the position ofvagus nerve150 relative tojugular vein158.Sensor222, in general, may be any suitable imaging or guidance system including, e.g., a fiberoptic endoscope, ultrasound imaging system, or any other on-board imaging system capable of positioningcatheter220 to advanceelectrode228 throughjugular vein158 towardvagus nerve150 by providing an image of the area adjacent the location ofsensor222 oncatheter220. In some examples,sensor222 could be an array of receivers in relationship to a transmitter that provide an image of surrounding tissue and structures includingvagus nerve150 andcarotid artery160. In other examples,sensor222 may be configured to send or receive signals to or from any of a series of known signal generators including sonic, electromagnetic, light or radiation signals. In still other examples,sensor222 may be an optical oxygen content sensor that may be used to ensure thatlead29 andelectrode228 are not directed toward, e.g.,carotid artery160 during lead placement. In some examples,sensor222 may be employed in conjunction with one or more opaque markers viewable with fluoroscopic techniques or with an irrigated lumen that dispenses contrast media to assist in imaging the position ofvagus nerve150 relative tojugular vein158. In still other examples,sensor222 may employed in addition to a separate optical oxygen content or venous biomarker sensor that may be used to ensure thatlead29 andelectrode228 are not directed toward, e.g.,carotid artery160 during lead placement. In some such examples, an optical oxygen content or venous biomarker sensor may be connected todeployment member224 to detect the presence of and reduce the risk of piercing or otherwise damagingcarotid artery160 asdeployment member224 includingelectrode228 is advanced through the wall of the lumen ofjugular vein158 towardvagus nerve150.
• In one example,sensor222 is an intravenous ultrasound (“IVUS”) imaging system that is adapted to radiate ultrasonic waves out fromsensor222 to generate a two dimensional image of the tissue andstructures surrounding catheter220 andsensor222. When activated,sensor222 may produce an imaging field from ultrasonic waves produced by and radiating radially fromcatheter220 and sensor222 (see, e.g.,FIG. 11). The size of the imaging field may vary depending on the particular configuration and capabilities ofsensor222. The tissues and other structures caught within the imaging field ofsensor222 may be distinguished from one another and the relative positioning of the different structures may be discerned. Therefore, in the context of transvacular lead placement,vagus nerve150,jugular vein158, andcarotid artery160 may be caught within the imaging field ofsensor222 to detect, e.g., the position ofnerve150 relative tovein158.
• Aftersensor222 identifies the location ofvagus nerve150 with respect tojugular vein158,deployment member224 includingelectrode228 may be advanced through the wall of the lumen ofjugular vein158 towardvagus nerve150.Deployment member224, in general, is extendable and retractable fromcatheter220 from, e.g., an aperture formed in a sidewall thereof.Deployment member224 includestubular member226, lead29,electrode228, andguidewire230.Tubular member226 may be any structure including at least one lumen through which various electrode deployment structures including, e.g., lead29 and guidewire230 may be advanced to place an electrode outside ofvein158adjacent vagus nerve150. In the example ofFIG. 19,tubular member226 may be a needle capable of piercing the wall of the lumen ofvein158 and including a lumen in which lead29 and guidewire230 are received and through which the same are advanceable.Electrode228 is connected to lead29, which is advanceable alongguidewire230.
• With the aid ofsensor222,deployment member224 is advanced fromcatheter220 throughjugular vein158 towardvagus nerve150.Lead29, to whichelectrode228 is connected, and guidewire230 may be advanced through a lumen ofdeployment member224 to positionelectrode228 outside ofvein158adjacent vagus nerve150.Guidewire230 includesanchor portion230A at a distal end thereof that is configured to anchordeployment member224, lead29 andelectrode228, and guidewire230 to tissue outside ofvein158. In the example ofFIG. 19,anchor portion230A includesguidewire230 formed in a spiral that is configured to be twisted tissueadjacent vagus nerve150.Anchor portion230A can be freed from the tissue by either untwistingguidewire230, or in the case that guidewire230 is sufficiently flexible, pulling the wire away from the spiralinganchor portion230A to effectively unwind and release the anchor from the tissue.
• Having deployedcatheter220, detected the location ofvagus nerve150 relative tojugular vein158, andadvanced electrode228 throughvein158 towardvagus nerve150, electrical stimulation may be delivered tovagus nerve150 viaelectrode228. A portion oflead29 extending away from a distal end toward which electrode228 is arranged may be guided to connect withIMD16. In one example, lead29 may be guided intravascularly to an implantation location ofIMD16 withinpatient12. In other examples, at least a portion oflead29 may be tunneled through tissue ofpatient12 to be connected toIMD16. Although the example ofFIGS. 18 and 19 is described with reference to implantedmedical device16 arranged withinpatient12, examples according to this disclosure also includelead29 connected transcutaneously to an external medical device that is configured to deliver electrical stimulation to the target nerve tissue, e.g.,vagus nerve150. Afterlead29 is placedadjacent vagus nerve150 outside ofjugular vein158 and connected toIMD16,IMD16, either automatically or as partially or completely commanded byprogrammer24, may deliver electrical stimulation therapy to and/or receive sensor feedback fromvagus nerve150 throughelectrode228.
• In the example ofFIGS. 18 and 19, as well as other examples disclosed herein, the efficacy of the electrical stimulation delivered byelectrode228 tovagus nerve150 may be compared to a threshold efficacy to determine whether or not electrode228 is satisfactorily positioned with respect tonerve150. Efficacy may be measured, in general, by verbal feedback frompatient12, clinician observation of various conditions ofpatient12, or sensory feedback from one or more devices including, e.g.,ICD17 shown inFIG. 1A orcardiac therapy module104 shown inFIG. 4. For example, to determine the response to stimulation ofvagus nerve150, ECG, heart rate, blood pressure, blood flow, cardiac output, and/or breathing, ofpatient12 can be sensed or observed. In another example, efficacy may be measured by a sensor including, e.g., an accelerometer that determines if stimulation of the neck muscles or phrenic nerve ofpatient12 is occurring with or instead of stimulation ofvagus nerve150.
• FIGS. 21A-21D show several alternative examples ofdeployment member224 for use in methods and systems according to this disclosure. In general,FIGS. 21A-21D show different arrangements and combinations of anchoring members and electrodes with respect totubular member226, lead29, and guidewire230 ofdeployment member224. In the interest of simplicity,catheter220 has been omitted from the illustrations ofFIGS. 21A and 21B. InFIG. 21A,deployment member224 is advanced through the lumen wall ofjugular vein158 towardvagus nerve150 and includestubular member226, lead29,electrode228, guidewire230, andexpandable member390. In some examples, it may be desirable or necessary to useexpandable member390 to enlarge the tract along whichtubular member226 and guidewire230 are advanced through andoutside vein158 prior to placinglead29 andelectrode228. In one example employingexpandable member390,tubular member226 and guidewire230 may be advanced through the lumen wall ofjugular vein158 towardvagus nerve150. Thereafter,expandable member390 may be advanced overguidewire230 and used to enlarge the tract along which lead29 andelectrode228 will be advanced. Theexpandable member390 may, in some examples, be a balloon catheter including, e.g., an angioplasty catheter. Instead of or in addition toexpandable member390, other tract enlarging devices may be employed including, e.g., electrosurgical debulking devices or tissue cutting devices.
• In addition to or in lieu of tract enlargement, in some examples,expandable member390 may provide additional stabilization or biasing oflead29 or other components ofdeployment member224 outside ofjugular vein158adjacent vagus nerve150. For example,expandable member390 may push against the exterior surface ofjugular vein158 as shown inFIG. 21A to bias lead29 andelectrode228 towardvagus nerve150. In another example,expandable member390 may further stabilize the placement oflead29 andelectrode228 by expanding to apply force onjugular vein158 andvagus nerve150.
• FIG. 21B showsdeployment member224 withanchor392. InFIG. 21B,deployment member224 is advanced through the lumen wall ofjugular vein158 towardvagus nerve150 and includestubular member226, lead29,electrode228, guidewire230, andanchor392.Anchor392 is connected to lead29 and is configured to securelead29 and thereby electrode228 to tissue outside ofjugular vein158adjacent nerve150.Anchor392 may be any number of structures that are actively or passively deployable from withintubular member226 to engage tissue withinpatient12. In the example ofFIG. 21B,anchor392 is in the form of passive tines or barbs that protrude fromlead29 and that may engage tissue outside ofjugular vein158 afterlead29 is advanced through and out oftubular member226. In other examples,anchor392 may come in different shapes and sizes including, e.g., helical coils, C-shaped members, harpoon-like structures, hooks, expandable or serrated members, and the like. InFIG. 21B,anchor392 is employed in lieu ofanchor portion230A ofguidewire230. However, in other examples bothanchor392 andanchor portion230A may be used to securely deploylead29 andelectrode228 outside ofjugular vein158adjacent vagus nerve150.
• The anchors illustrated inFIGS. 14A-14J and described with reference to intravascular lead placement techniques may also be used in transvascular techniques disclosed herein. One or more of the anchors illustrated inFIGS. 14A-14J may be employed, for example, alone or in combination in a manner as described with reference to anchorportion230A ofguidewire230 inFIG. 19. In such examples,anchor portion230A ofguidewire230 may take an alternative form to that shown inFIG. 19 including, e.g., the harpoon anchors ofFIGS. 14B and 14C. In another example, one of the illustrated anchors ofFIGS. 14A-14J may be employed asanchor392 shown inFIG. 21B.
• FIG. 21C showscatheter220 withadditional electrode394 anddeployment member224 withadditional electrode396 connected totubular member226. InFIG. 21C,deployment member224 is advanced through the lumen wall ofjugular vein158 towardvagus nerve150 and includestubular member226, lead29,electrode228, guidewire230, andadditional electrodes394,396. Although transvascular placement examples oflead29 have been described herein with reference to asingle electrode228 for simplicity, in practice, lead29 will commonly include a plurality of electrodes that may be employed in different anode and cathode combinations to stimulatevagus nerve150 as, e.g., described with reference to electrodes80-83 inFIG. 2.
• Additionally and as illustrated inFIG. 21C,catheter220 may includeelectrode394 in addition tolead electrode228. In the example ofFIG. 21C,deployment member224 may be advanced through the wall ofjugular vein158 and thereafter used to pullcatheter220 andelectrode394 toward the lumen wall withinjugular vein158. For example,deployment member224 may include an active or passive anchor (e.g. anchor portion230A ofFIG. 21A, oranchor392 ofFIG. 21B) that fixesdeployment member224 outside ofvein158adjacent vagus nerve150. Afterdeployment member224 is anchored outside ofjugular vein158,catheter220 may be pulled alongdeployment member224 to abut the wall of the lumen ofjugular vein158 as shown inFIG. 21C, thereby positioningelectrode394 within the veinproximate vagus nerve150.
• Deployment member224 may also include electrodes in addition tolead electrode228 arranged in different locations and/or connected to different components. InFIG. 21C,electrode396 is connected totubular member226. In some examples,tubular member226 andelectrode396 may be advanced through the wall ofvein158 towardvagus nerve150 prior to chronically deployinglead29 andelectrode228. In such examples,electrode396 may be used to deliver test stimulation pulses tovagus nerve150 to determine the efficacy of the placement ofdeployment member224 outside ofjugular vein158 with respect tovagus nerve150. After determining a position of deployment member that provides a threshold efficacy in stimulatingvagus nerve150, lead29 and guidewire230 may be advanced throughtubular member226 and lead29 andelectrode228 may be chronically deployed along the wall of the lumen ofjugular vein158adjacent vagus nerve150.
• FIG. 21D showsguidewire230 and lead29 deployed transvascularly to create a cuff arrangement that wraps aroundvagus nerve150. InFIG. 21D,deployment member224 is advanced through the lumen wall ofjugular vein158 towardvagus nerve150 and includestubular member226, lead29,electrode228, andguidewire230. In some examples, it may be desirable to anchor and/or localize the stimulation field delivered by electrodes connected to lead29 around the nerve. In one example, a curved member may be deployed fromtubular member226 to loop and thereby create a cuff aroundvagus nerve150. The curved member may be, e.g., a tubular needle adapted to receiveguidewire230 and/or lead29. In the example ofFIG. 21D, the curved member is guidewire230, which is advanced fromtubular member226 ofdeployment member224 aroundvagus nerve150. Afterguidewire230 is arranged aroundnerve150, lead29 andelectrode228 may be advanced along the guidewire to wrap around the nerve.
• In certain applications, transvascular lead placement may carry certain inherent risks. In some examples, advancing medical leads from within a lumen of a blood vessel, through a wall of the vessel to place the leads adjacent nerve tissue in an extravascular space may carry the risk of piercing or otherwise damaging other neighboring biological structures including, e.g., other blood vessels. In the context of vagal nerve stimulation/sensing examples disclosed herein, for example, transvascularly placing a leadadjacent vagus nerve150 may carry the risk of piercing or otherwise causing damage tocarotid artery160 adjacent the nerve andjugular vein158. Therefore, in some examples according to this disclosure, transvascular lead placement techniques may employ a deployment member part or all of which is constructed from a shape memory material such that the deployment member is configured to pass laterally through a vessel wall and turn outside of the vessel to be arranged longitudinally along the vessel adjacent the target nerve tissue. In this way, the deployment member and other components of the transvascular lead placement apparatus may reduce the risk of advancing too far laterally from the blood vessel and, e.g., piercing an adjacent vessel such as an artery.
• FIG. 22 shows one example ofdeployment member224 employingtubular member226 constructed from a shape memory material. Examples disclosed herein may use a variety of shape memory materials including, e.g., nickel titanium (NiTi) alloys. NiTi is a shape memory alloy, which is sometimes referred to as Nitinol. Other shape-memory alloys may also be used in examples disclosed herein including, e.g., copper tin (CuSn), indium titanium (InTi), and manganese copper (MnCu) alloys. A reversible, solid phase transformation known as martensitic transformation is the physical mechanism that underpins shape memory materials. Generally speaking, shape memory materials form a crystal structure that can undergo a change from one crystal form to another initiated by a temperature change or application of force. Above its transformation temperature, Nitinol, e.g., is superelastic, able to withstand a small amount of deformation when a load is applied and return to its original shape when the load is removed. Below its transformation temperature, it displays the shape memory effect. When it is deformed it will remain in that shape until heated above its transformation temperature, at which time it will return to its original shape. Nitinol is typically composed of approximately 50 to 55.6% nickel by weight. However, small changes in material composition can change the transition temperature of the alloy significantly. As such, Nitinol may or may not be superelastic at room temperature. The flexibility and unique properties of Nitinol to be used in a wide range of temperatures makes it suitable for many applications, particularly in medicine.
• InFIG. 22,deployment member224 includestubular member226, lead29,electrode228, andguidewire230.Tubular member226 may be any structure including at least one lumen through which various electrode deployment structures including, e.g., lead29 and guidewire230 may be advanced to place an electrode outside ofvein158adjacent vagus nerve150. In the example ofFIG. 22,tubular member226 may be a needle capable of piercing the wall of the lumen ofvein158 and including a lumen in which lead29 and guidewire230 are received and through which the same are advanceable.Electrode228 is connected to lead29, which is advanceable alongguidewire230.
• Deployment member224 is advanced fromcatheter220 throughjugular vein158 towardvagus nerve150.Lead29, to whichelectrode228 is connected, and guidewire230 may be advanced through a lumen ofdeployment member224 to positionelectrode228 outside ofvein158adjacent vagus nerve150. In the example ofFIG. 22,tubular member226 is constructed from a shape memory material including, e.g., Nitonol and generally takes an S-shape after being advanced through the lumen of from catheter220 (shown inFIG. 19) through the wall ofjugular vein158. The material properties and shape oftubular member226 reduce the risk that the needle, or another component ofdeployment member224 will advance too far laterally fromjugular vein158 and, e.g., pierce or otherwise damagecarotid artery160. Aftertubular member226 is advanced through the wall ofvein158, guidewire230 may be deployed and lead29 andelectrode228 may be advanced alongguidewire230 to arrangeelectrode228adjacent vagus nerve150.
• In other examples according to this disclosure, other components ofdeployment member224 may be constructed from a shape memory material. For example, guidewire230 may, in addition to or in lieu oftubular member226, be constructed from a shape memory material including, e.g., Nitonol. In some such examples,tubular member226 ofdeployment member224 is advanced fromcatheter220 towardvagus nerve150.Lead29, to whichelectrode228 is connected, and guidewire230 may be advanced through a lumen oftubular member226 to positionelectrode228 outside ofvein158adjacent vagus nerve150. In particular, guidewire230 is constructed from a shape memory material and generally takes an S-shape to pass out oftubular member226, through the wall ofvein158, and run longitudinally along and adjacent tovagus nerve150 outside ofvein158. Afterguidewire230 is advanced through the wall ofvein158, lead29 andelectrode228 may be advanced alongguidewire230 to arrangeelectrode228adjacent vagus nerve150.
• The extra, intra, and transvascular lead placement techniques disclosed herein may benefit, in some examples, from electrode pairs arranged in flanking, non-contacting relationship with the target nerve tissue. In one example, multiple leads are arranged longitudinally on opposing sides of and including electrodes in non-contacting relationship with the target nerve tissue. In another example, a single lead including multiple electrodes is arranged such that at least two of the electrodes are arranged on opposing sides of and in non-contacting relationship with the target nerve tissue. Such flanking, non-contacting electrode arrangements may provide one or more anode and cathode electrode combinations for electrical stimulation across the target nerve tissue without the deleterious effects of tissue contacting techniques, such as may be caused by, e.g., cuff electrodes.
• FIGS. 23A and 23B illustrate example arrangements of electrode pairs in flanking, non-contacting relationship withvagus nerve150. The example ofFIG. 23A includes multiple leads and may be applicable to different combinations of intra, extra, and transvascular lead placement techniques disclosed herein. The example ofFIG. 23B includes a single lead including a pair of electrodes in flanking, non-contacting relationship withvagus nerve150. The example ofFIG. 23B may be generally applicable to extra and transvascular lead placement techniques according to this disclosure.
• The example ofFIG. 23A includes leads400 and402, andelectrodes228. InFIG. 23A,Lead400 is arranged longitudinally along one side ofvagus nerve150.Lead402 is arranged longitudinally along a generally opposing side ofvagus nerve150 across fromlead400. Each ofleads400 and402 include a plurality ofelectrodes228 connected to the distal end of each lead. In the example ofFIG. 23A, each lead400 and402 includes fourelectrodes228. However, in other examples, leads400,402 may include fewer or more electrodes and may include different numbers of electrodes. Additionally, althoughFIG. 23A shows twoleads400,402, other examples may include more than two leads including, e.g., four or six leads, two of each of which are respectively arranged longitudinally on opposing sides of and including electrodes in non-contacting relationship withvagus nerve150.
• The example leads400 and402 shown inFIG. 23A may be placed withinpatient12 according to different combinations of intra, extra, and transvascular lead placement techniques disclosed herein. For example, lead400 may be placed intravscularly withinjugular vein158adjacent vagus nerve150, whilelead402 is placed extravascularly withincarotid sheath156. In another example, lead400 may be placed intravscularly withinjugular vein158adjacent vagus nerve150, whilelead402 is placed transvascularly through the wall ofvein158 to an extravascular location adjacent the nerve. In still another example, both leads400 and402 may be placed extravascularly withincarotid sheath156adjacent vagus nerve150. Similarly, both leads400 and402 may be placed transvascularly through the wall ofvein158 to an extravascular locationadjacent vagus nerve150.
• Pairs ofelectrodes228 fromleads400,402 may be employed to provide one or more anode/cathode combinations for electrical stimulation acrossvagus nerve150. The neurostimulator or other device to which leads400,402 are connected may include a switching module as described with reference toneurostimulation module106 ofIMD16 inFIG. 2. The switching module may selectively couple pairs ofelectrodes228 to a signal generator and/or sensing module to form different anode-cathode combinations as indicated by dashedelectrical field lines404 inFIG. 23A. The switching module may include, e.g., a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple stimulation energy to selected electrodes.
• The example ofFIG. 23B showsdeployment member224 that is configured to be advanced and retracted from, e.g., a delivery catheter (not shown inFIG. 23B) through the wall ofjugular vein158 towardvagus nerve150.Deployment member224 includestubular member226, lead29, and a pair ofelectrodes228.Tubular member226 may be any structure including at least one lumen through which various electrode deployment structures including, e.g., lead29 and a guide member may be advanced to place anelectrodes228 in flanking, non-contacting relationship withvagus nerve150.Electrodes228 are connected to lead29, which is advanceable through tubular member along, e.g., a guide wire or stylus. In the example ofFIG. 23B, lead29 includes twoelectrodes228. However, in other examples, lead29 may include more electrodes including, e.g., four or six electrodes arranged in opposing pairs with respect tovagus nerve150.
• Deployment member224 is advanced throughjugular vein158 towardvagus nerve150.Lead29, to whichelectrodes228 are connected, may be advanced through a lumen oftubular member226 to position oneelectrode228 insidejugular vein158 and oneelectrode228 outside ofvein158 such that the twoelectrodes228flank vagus nerve150 as shown inFIG. 23B. In the example ofFIG. 23B, lead29 andelectrodes228 may be guided along, e.g., a guidewire that is constructed from a shape memory material as described with reference toFIG. 22. Although the example ofFIG. 23B illustrateslead29 andelectrodes228 placed transvascularly, other examples may include lead29 placed extravascularlyadjacent vagus nerve150 incarotid sheath156. Afterlead29 andelectrodes228 are placed with respect tovagus nerve150, the pair of electrodes may be employed to provide electrical stimulation acrossvagus nerve150. In some examples, the neurostimulator or other device to whichlead29 is connected may include a signal generator and/or sensing module to couple and energizeelectrodes228 in anode-cathode combinations to stimulatevagus nerve150 as indicated by dashedelectrical field line404 inFIG. 23B.
• Examples according to this disclosure generally provide medical lead placement proximate nerve tissue within a patient for electrical stimulation of the tissue without the use of potentially deleterious electrode configurations including e.g., cuff electrodes. Techniques disclosed herein also generally provide flexible placement techniques and structures by employing one or more temporary lead placements and stimulation tests, prior to chronically placing the leads within the patient for nerve tissue stimulation. Furthermore, techniques according to this disclosure are adapted to enable minimally invasive introduction of the medical leads into the patient. Implantable electrical stimulation systems and methods in accordance with this disclosure may be used to deliver therapy to patients suffering from conditions that range from chronic pain, tremor, Parkinson's disease, and epilepsy, to urinary or fecal incontinence, sexual dysfunction, obesity, spasticity, and gastroparesis. Specific types of electrical stimulation therapies for treating such conditions include, e.g., cardiac pacing, neurostimulation, muscle stimulation, or the like.
• Various examples have been described in this disclosure. These and other examples are within the scope of the following claims.

Claims (34)

1. A system for implantation of a medical lead configured to deliver electrical stimulation to nerve tissue located adjacent a blood vessel, the system comprising:

a catheter adapted to be positioned within a lumen of the blood vessel adjacent the nerve tissue;

a deployment member extendable and retractable from the catheter through a wall of the blood vessel lumen; and

an electrode connected to the deployment member such that the deployment member positions the electrode outside of the blood vessel proximate the nerve tissue when the deployment member is extended through the lumen wall.

2. The system ofclaim 1 further comprising a sensor configured to detect the position of the nerve tissue relative to the blood vessel.

3. The system ofclaim 2, wherein the sensor is connected to the catheter between a distal end of the catheter and a location along the catheter from which the deployment member is extendable and retractable.

3. The system ofclaim 1, wherein the deployment member comprises:

a guide member; and

a medical lead advancable along the guide member.

4. The system ofclaim 3 further comprising a tubular member, wherein the guide member and the lead are received within and advanceable through a lumen of the tubular member.

5. The system ofclaim 4, wherein the electrode is connected to one of the tubular member or the lead.

6. The system ofclaim 4, wherein the tubular member comprises a needle adapted to pierce the wall of the blood vessel lumen.

7. The system ofclaim 4, wherein the tubular member comprises a shape memory material configured to assume an S-shape.

8. The system ofclaim 7, wherein the tubular member comprises a nickel titanium alloy.

9. The system ofclaim 3, wherein the electrode is connected to the lead.

10. The system ofclaim 3 further comprising an anchor connected to and configured to anchor the deployment member outside of the blood vessel adjacent the nerve tissue.

11. The system ofclaim 10, wherein a distal end of the guide member comprises the anchor.

12. The system ofclaim 11, wherein the anchor comprises the distal end of the guide member formed in a spiral shape configured to screw into tissue outside of the blood vessel adjacent the nerve tissue.

13. The system ofclaim 10, wherein the anchor is connected to the guide member.

14. The system ofclaim 3, wherein the guide member is one of a guidewire or a stylus.

15. The system ofclaim 3, wherein the guide member is configured to wrap at least partially around the nerve tissue.

16. The system ofclaim 3, wherein the guide member comprises a shape memory material configured to assume an S-shape.

17. The system ofclaim 16, wherein the guide member comprises a nickel titanium alloy.

18. The system ofclaim 1 further comprising an anchor connected to and configured to anchor the deployment member outside of the blood vessel adjacent the nerve tissue.

19. The system ofclaim 1, further comprising one or more additional electrodes coupled to one or more implantable medical leads, wherein at least one of the one or more implantable medical leads is received within and advanceable from the deployment member when advanced through the wall of the blood vessel lumen to position the lead electrode adjacent the nerve tissue, and wherein at least two of the electrodes are arranged in flanking, non-contacting relationship with the nerve tissue.

20. The system ofclaim 19, wherein another of the one or more implantable medical leads comprises an extravascularly placed lead or an intravascularly placed lead.

21. The system ofclaim 1 further comprising a physiological sensor configured to detect one or more physiological signals from the patient.

22. The system ofclaim 21, wherein the physiological sensor comprises one of a sense electrode, pressure sensor, ultrasound sensor, motion sensor, acoustic sensor, optical sensor, blood oxygen sensor, posture state sensor, respiration sensor, venous biomarker sensor, or temperature sensor.

23. The system ofclaim 21, wherein the physiological sensor is configured to detect one or more of electrocardiogram, heart rate, blood pressure, blood flow, blood oxygen content, blood biomarker content, cardiac output, respiratory activity, nerve signals, T-wave morphology, heart rate variability, contractility, or AV intervals.

24. The system ofclaim 1, wherein the nerve tissue comprises one of a vagus nerve, a hypoglossal nerve, a nerve plexus, nerve ganglia, or a vascular baroreceptors.

25. A method comprising:

deploying a delivery catheter through a lumen of a blood vessel to a location proximate a target nerve tissue site outside the blood vessel;

identifying a location of the nerve tissue with respect to the blood vessel with one or more sensors connected to the delivery catheter; and

advancing an electrical stimulation electrode from the catheter through a wall of the blood vessel toward the nerve tissue.

26. The method ofclaim 25 further comprising energizing the electrode to deliver electrical stimulation to the nerve tissue.

27. The method ofclaim 26 further comprising determining an efficacy of the nerve tissue stimulation.

28. The method ofclaim 27 further comprising comparing the efficacy of the nerve tissue stimulation to a threshold efficacy.

29. The method ofclaim 25 further comprising anchoring the electrode outside of the blood vessel adjacent the nerve tissue.

30. The method ofclaim 25, wherein advancing the electrical stimulation electrode through the wall of the blood vessel toward the nerve tissue comprises:

wrapping a guide member at least partially around the nerve tissue; and

advancing the electrode along the guide member.

31. The method ofclaim 25 further comprising arranging at least one additional electrical stimulation electrode adjacent the nerve tissue such that at least two electrodes are arranged in flanking, non-contacting relationship with the nerve tissue.

32. The method ofclaim 31, wherein the at least one additional electrode is connected to one of an extra, intra, or transvascularly placed lead.

33. The method ofclaim 25, wherein the nerve tissue comprises one of a vagus nerve, a hypoglossal nerve, a nerve plexus, nerve ganglia, or a vascular baroreceptor.

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