US20050143727A1 - Surgical probe for supporting inflatable therapeutic devices in contact with tissue in or around body orifices and within tumors - Google Patents

Abstract

A probe that facilitates the creation of lesions in bodily tissue. The probe includes a relatively short shaft and an inflatable therapeutic element.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation-in-part of U.S. application Ser. No. 09/083,874, filed May 22, 1998, which is incorporated herein in its entirety.
BACKGROUND OF THE INVENTIONS
• 1. Field of Inventions
• The present inventions relate generally to surgical probes that support therapeutic devices in contact with body tissue.
• 2. Description of the Related Art
• There are many instances where diagnostic and therapeutic elements must be inserted into the body. One instance involves the treatment of cardiac conditions such as atrial fibrillation and atrial flutter which lead to an unpleasant, irregular heart beat, called arrhythmia.
• Normal sinus rhythm of the heart begins with the sinoatrial node (or “SA node”) generating an electrical impulse. The impulse usually propagates uniformly across the right and left atria and the atrial septum to the atrioventricular node (or “AV node”). This propagation causes the atria to contract in an organized way to transport blood from the atria to the ventricles, and to provide timed stimulation of the ventricles. The AV node regulates the propagation delay to the atrioventricular bundle (or “HIS” bundle). This coordination of the electrical activity of the heart causes atrial systole during ventricular diastole. This, in turn, improves the mechanical function of the heart. Atrial fibrillation occurs when anatomical obstacles in the heart disrupt the normally uniform propagation of electrical impulses in the atria. These anatomical obstacles (called “conduction blocks”) can cause the electrical impulse to degenerate into several circular wavelets that circulate about the obstacles. These wavelets, called “reentry circuits,” disrupt the normally uniform activation of the left and right atria.
• Because of a loss of atrioventricular synchrony, the people who suffer from atrial fibrillation and flutter also suffer the consequences of impaired hemodynamics and loss of cardiac efficiency. They are also at greater risk of stroke and other thromboembolic complications because of loss of effective contraction and atrial stasis.
• One surgical method of treating atrial fibrillation by interrupting pathways for reentry circuits is the so-called “maze procedure” which relies on a prescribed pattern of incisions to anatomically create a convoluted path, or maze, for electrical propagation within the left and right atria. The incisions direct the electrical impulse from the SA node along a specified route through all regions of both atria, causing uniform contraction required for normal atrial transport function. The incisions finally direct the impulse to the AV node to activate the ventricles, restoring normal atrioventricular synchrony. The incisions are also carefully placed to interrupt the conduction routes of the most common reentry circuits. The maze procedure has been found very effective in curing atrial fibrillation. However, the maze procedure is technically difficult to do.
• Maze-like procedures have also been developed utilizing catheters which can form lesions on the endocardium (the lesions being 1 to 15 cm in length and of varying shape) to effectively create a maze for electrical conduction in a predetermined path. The formation of these lesions by soft tissue coagulation (also referred to as “ablation”) can provide the same therapeutic benefits that the complex incision patterns that the surgical maze procedure presently provides.
• Catheters used to create lesions typically include a relatively long and relatively flexible body portion that has a soft tissue coagulation electrode on its distal end and/or a series of spaced tissue coagulation electrodes near the distal end. The proximal end of the flexible body is typically connected to a handle which includes steering controls. The portion of the catheter body portion that is inserted into the patient is typically from 58.4 cm to 139.7 cm in length and there may be another 20.3 cm to 38.1 cm, including a handle, outside the patient. The length and flexibility of the catheter body allow the catheter to be inserted into a main vein or artery (typically the femoral artery), directed into the interior of the heart, and then manipulated such that the coagulation electrode contacts the tissue that is to be ablated. Linear and curvilinear lesions can then be created by dragging a single electrode or by applying power (preferably simultaneously) to the series of spaced electrodes.
• Catheter-based soft tissue coagulation has proven to be a significant advance in the medical arts generally and in the treatment of cardiac conditions in particular. Nevertheless, the inventors herein have determined that catheter-based procedures are not appropriate in every situation and that conventional catheters are not capable of reliably forming all types of lesions. For example, one lesion that has proven to be difficult to form with conventional catheter devices is the circumferential lesion that is used to isolate the pulmonary vein and cure ectopic atrial fibrillation. Lesions that isolate the pulmonary vein may be formed within the pulmonary vein itself or in the tissue surrounding the pulmonary vein. These circumferential lesions are formed by dragging a tip electrode around the pulmonary vein or by creating a group of interconnected curvilinear lesions one-by-one around the pulmonary vein. Such techniques have proven to be less than effective because they are slow and gaps of conductive tissue can remain after the procedure. It can also be difficult to achieve the adequate tissue contact with conventional catheters.
• Accordingly, the inventors herein have determined that a need exists for structures that can be used to create circumferential lesions within or around bodily orifices and, in the context of the treatment of atrial fibrillation, within or around the pulmonary vein.
• Another instance where therapeutic elements are inserted into the body is the treatment of tumors, such as the cancerous tumors associated with breast cancer and liver cancer. Heretofore, tumors have been treated with highly toxic drugs that have proven to have severe side effects. More recently, devices including a plurality of needle-like electrodes have been introduced. The needle-like electrodes may be directed into the tumor tissue and used to deliver RF energy. The associated current flow heats the tissue and causes it to coagulate.
• The inventors herein have determined that there are a number of shortcomings associated with the use of needle-like electrodes to coagulate tissue. Most notably, the needle-like electrodes produce non-uniform, shallow lesions and/or spot lesions and also fail to coagulate the entire volume of tumor tissue. This failure can ultimately result in the tumor growing to be even larger than its original size. The needle-like electrodes can also cause tissue charring. Moreover, tissue tends to shrink around the needle-like electrodes during the coagulation process. This makes it very difficult to withdraw the electrodes from the patient and often results in tissue trauma.
• Accordingly, the inventors herein have determined that a need exists for a device that can completely and uniformly coagulate large volumes of tissue without charring and can also be removed from the patient without the difficulty associated with needle-like electrodes.
SUMMARY OF THE INVENTION
• Accordingly, the general object of the present inventions is to provide a device that avoids, for practical purposes, the aforementioned problems. In particular, one object of the present inventions is to provide a device that can be used to create circumferential lesions in or around the pulmonary vein and other bodily orifices in a more efficient manner than conventional apparatus.
• In order to accomplish some of these and other objectives, a surgical probe in accordance with one embodiment of a present invention includes a relatively short shaft and an inflatable therapeutic element associated with the distal portion of the shaft. In a preferred embodiment, the therapeutic element will be configured so that it can form a continuous lesion around a pulmonary vein.
• Such a probe provides a number of advantages over conventional apparatus. For example, the present surgical probe may be used during open heart surgery or in less invasive procedures where access to the heart is obtained via a thoracostomy, thoracotomy or median stemotomy. The relatively short shaft and manner in which access is obtained allows the therapeutic element to be easily inserted into the heart and placed against the target tissue with the desired level of contact, thereby eliminating many of the problems associated with catheter-based procedures. Moreover, the present therapeutic element may be used to form lesions in an annular region of tissue within or around the pulmonary vein (or other orifice in other procedures) in one step, thereby eliminating the need to either drag a tip electrode around an annular region or form a number of interconnected curvilinear lesions that is associated with catheter-based procedures.
• Additionally, in accordance with a preferred embodiment, the flexibility of the inflatable therapeutic element may be varied as appropriate. This allows the physician to achieve the appropriate level of tissue contact, even when the shaft is not perfectly perpendicular to the target tissue area, the target tissue area is somewhat uneven, or the target tissue has become rigid due to calcification.
• In accordance with another preferred embodiment, the inflatable therapeutic element will be configured such that it can be inserted into a tumor (or other target location), inflated and then used to uniformly coagulate the entire tumor (or a large volume of tissue associate with the other location) without charring. Once the coagulation procedure is complete, the inflatable therapeutic element can be deflated and removed from patient without the difficulty and trauma associated with needle-like electrodes.
• In order to accomplish some of these and other objectives, a surgical probe in accordance with one embodiment of a present invention includes hollow needle and a therapeutic assembly, located within the hollow needle and movable relative thereto, having a relatively short shaft and an inflatable therapeutic element associated with the distal portion of the shaft. The hollow needle may be used to pierce through tissue to enter a target location such as a tumor. Prior to coagulation, the hollow needle may be withdrawn and the inflatable therapeutic element held in place within the tumor. The therapeutic element may then be inflated and the tissue coagulated. When the coagulation procedure is complete, the therapeutic element may be deflated and withdrawn back into the hollow needle.
• In order to accomplish some of these and other objectives, a surgical probe in accordance with one embodiment of a present invention includes one or more needles having inflatable porous therapeutic elements mounted thereon. The needles may be directed into tissue, such as tumor tissue for example, in a manner similar to conventional needle electrodes. Here, however, conductive fluid within the inflatable porous therapeutic elements will draw heat away from the therapeutic element and the adjacent tissue. Such heat transfer results in the formation of relatively deep, large volume lesions without the charring and coagulation associated with conventional needle electrodes.
• The above described and many other features and attendant advantages of the present inventions will become apparent as the inventions become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
• Detailed description of preferred embodiments of the inventions will be made with reference to the accompanying drawings.
• FIG. 1 is a side view of a surgical probe in accordance with a preferred embodiment of a present invention.
• FIG. 2 is a section view taken along line2-2 inFIG. 1.
• FIG. 3 is a cutaway view of the distal portion of the exemplary surgical probe illustrated inFIG. 1.
• FIG. 4 is a front view of the exemplary surgical probe illustrated inFIG. 1.
• FIG. 5 is a section view taken along line5-5 inFIG. 3.
• FIG. 6 is rear view of the exemplary surgical probe illustrated inFIG. 1 with the fluid lumens removed.
• FIG. 7 is a side view showing the exemplary surgical probe illustrated inFIG. 1 connected to a fluid supply and a power supply.
• FIG. 8 is a side view of a surgical probe in accordance with a preferred embodiment of a present invention.
• FIG. 9 is a side view of a surgical probe in accordance with a preferred embodiment of a present invention.
• FIG. 10 is a partial section view of the distal portion of the surgical probe illustrated inFIG. 9.
• FIG. 11 is a side view of the distal portion of a surgical probe in accordance with a preferred embodiment of a present invention.
• FIG. 12 is a side view of a surgical probe in accordance with a preferred embodiment of a present invention.
• FIG. 13 is an enlarged view of one of the needles in the surgical probe illustrated inFIG. 12.
• FIG. 14 is a partial section view of a portion of one of the needles in the surgical probe illustrated inFIG. 12.
• FIG. 15 is a section view taken along line15-15 inFIG. 13.
• FIG. 16 is a section view taken along line16-16 inFIG. 13.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• The following is a detailed description of the best presently known modes of carrying out the inventions. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the inventions.
• This specification discloses a number of probe structures, mainly in the context of cardiac ablation, because the structures are well suited for use with myocardial tissue. For example, the present inventions are designed to produce intimate tissue contact with target substrates associated with arrhythmias such as atrial fibrillation. One application is the creation of lesions within or around the pulmonary vein to treat ectopic atrial fibrillation. Nevertheless, it should be appreciated that the structures are applicable for use in therapies involving other types of soft tissue. For example, various aspects of the present inventions have applications in procedures concerning other regions of the body such as the prostate, liver, brain, gall bladder, uterus and other solid organs.
• As illustrated for example inFIGS. 1-7, asurgical probe10 in accordance with a preferred embodiment of a present invention includes a relativelyshort shaft12, an inflatabletherapeutic element14 and ahandle16. The relativelyshort shaft12 will typically be between 10.1 cm and 45.7 cm in length, and is preferably about 17.8 cm in length, while the outer diameter of the shaft is preferably between about 6 and 24 French.
• Force is applied through theshaft12 in order to achieve the appropriate level of tissue contact. Thus, theshaft12 should be sufficiently strong to prevent collapse when the force is applied and is preferably relatively stiff. As used herein the phrase “relatively stiff” means that the shaft12 (or other structural element) is either rigid, malleable, or somewhat flexible. A rigid shaft cannot be bent. A malleable shaft is a shaft that can be readily bent by the physician to a desired shape, without springing back when released, so that it will remain in that shape during the surgical procedure. Thus, the stiffness of a malleable shaft must be low enough to allow the shaft to be bent, but high enough to resist bending when the forces associated with a surgical procedure are applied to the shaft. A somewhat flexible shaft will bend and spring back when released. However, the force required to bend the shaft must be substantial. Rigid and somewhat flexible shafts are preferably formed from stainless steel, while malleable shafts are formed from fully annealed stainless steel.
• In the illustrated embodiment, theshaft12 consists of ahypotube18 with anouter polymer jacket20 and includes aproximal portion22 and adistal portion24, both of which are malleable. Theproximal portion22 is, however, stiffer than thedistal portion24. Theproximal portion22 is also longer (about 11.5 cm) than the distal portion24 (about 6.4 cm).
• One method of quantifying the flexibility of a shaft, be it shafts in accordance with the present inventions or the shafts of conventional catheters, is to look at the deflection of the shaft when one end is fixed in cantilever fashion and a force normal to the longitudinal axis of the shaft is applied somewhere between the ends. Such deflection (σ) is expressed as follows:
  σ=WX²(3L−X)/6EI
  where:
• • W is the force applied normal to the longitudinal axis of the shaft,
  • L is the length of the shaft,
  • X is the distance between the fixed end of the shaft and the applied force,
  • E is the modulous of elasticity, and
  • I is the moment of inertia of the shaft.
    When the force is applied to the free end of the shaft, deflection can be expressed as follows:
    σ=WL³/3EI
    Assuming that W and L are equal when comparing different shafts, the respective E and I values will determine how much the shafts will bend. In other words, the stiffness of a shaft is a function of the product of E and I. This product is referred to herein as the “bending modulus.” E is a property of the material that forms the shaft, while I is a function of shaft geometry, wall thickness, etc. Therefore, a shaft formed from relatively soft material can have the same bending modulus as a shaft formed from relatively hard material, if the moment of inertia of the softer shaft is sufficiently greater than that of the harder shaft.
• For example, a relatively stiff 5.1 cm shaft (either malleable or somewhat flexible) would have a bending modulus of at least approximately 28 N-cm²(1 lb.-in.²). Preferably, a relatively stiff 5.1 cm shaft will have a bending modulus of between approximately 86 N-cm²(3 lb.-in.²) and approximately 1435 N-cm²(50 lb.-in.²). By comparison, 5.1 cm piece of a conventional catheter shaft, which must be flexible enough to travel through veins, typically has bending modulus between approximately 2.8 N-cm²(0.1 lb.-in.²) and approximately 8.6 N-cm²(0.3 lb.-in.²). It should be noted that the bending modulus ranges discussed here are primarily associated with initial deflection. In other words, the bending modulus ranges are based on the amount of force, applied at and normal to the free end of the longitudinal axis of the cantilevered shaft, that is needed to produce 2.5 cm of deflection from an at rest (or no deflection) position.
• As noted above, the deflection of a shaft depends on the composition of the shaft as well as its moment of inertia. The shaft could be made of polymeric material, metallic material or a combination thereof. By designing theshaft12 to be relatively stiff (and preferably malleable), the present surgical probe is better adapted to the constraints encountered during the surgical procedure. The force required to bend a relatively stiff 5.1 cm long shaft should be in the range of approximately 6.7 N (1.5 lbs.) to approximately 53.4 N (12 lbs.). By comparison, the force required to bend a 5.1 cm piece of conventional catheter shaft should be between approximately 0.9 N (0.2 lb.) to 1.1 N (0.25 lb.). Again, such force values concern the amount of force, applied at and normal to the free end of the longitudinal axis of the cantilevered shaft, that is needed to produce 2.5 cm of deflection from an at rest (or no deflection) position.
• Ductile materials are preferable in many applications because such materials can deform plastically before failure. Materials are classified as either ductile or brittle, based upon the percentage of elongation before failure. A material with more than 5 percent elongation prior to fracture is generally considered ductile, while a material with less than 5 percent elongation prior to fracture is generally considered brittle.
• Alternatively, theshaft12 could be a mechanical component similar to shielded (metal spiral wind jacket) conduit or flexible Loc-Line®, which is a linear set of interlocking ball and socket linkages that can have a center lumen. These would be hinge-like segmented sections linearly assembled to make the shaft.
• Turning toFIGS. 3, and4, the exemplary inflatabletherapeutic element14 is formed from an electrically non-conductive or semi-conductive thermoplastic or thermosetting plastic material and includes a forward facingporous region26 havingmicropores28 andnon-porous regions30. Fluid pressure is used to inflate thetherapeutic element14 and maintain it in its expanded state in the manner described below. The fluid used to fill thetherapeutic element14 is an electrically conductive fluid that establishes an electrically conductive path to convey RF energy from theporous region26 to tissue.
• Although other shapes (such as oval, triangular and rectangular) and sizes may be employed, the exemplary inflatabletherapeutic element14 is substantially circular in cross section has a diameter between about 1.0 cm to about 3.0 cm at its widest point when inflated. A preferred inflated diameter is about 1.5 cm. The forward facingporous region26, which will have a width of about 1 mm to about 6 mm, is perpendicular to the longitudinal axis of theshaft12. Such shapes and sizes are well suited for use with pulmonary veins because they allow theporous region26 to be placed directly in contact with the targeted tissue area by a physician during open heart surgery. Nevertheless, other inflatable therapeutic element configurations, such as those where the entire forward facing half is porous, a solid circular portion of the forward facing half is porous, or the entire element is porous, may be employed as applications dictate.
• Referring more specifically toFIG. 3, anelectrode32 is carried within the exemplary inflatabletherapeutic element14. Theelectrode32 should be formed from material with both relatively high electrical conductivity and relatively high thermal conductivity. Suitable materials for theelectrode32, the length of which preferably ranges from about 1 mm to 6 mm, include gold, platinum, and platinum/iridium. Noble metals are preferred. Themicropores28 establish ionic transport of the tissue coagulating energy from theelectrode32 through the electrically conductive fluid to tissue outside thetherapeutic element14.
• The electrically conductive fluid preferably possesses a low resistivity to decrease ohmic loses and thus ohmic heating effects within thetherapeutic element14. The composition of the electrically conductive fluid can vary. A hypertonic saline solution, having a sodium chloride concentration at or near saturation, which is about 20% weight by volume is preferred. Hypertonic saline solution has a low resistivity of only about 5 ohm-cm, compared to blood resistivity of about 150 ohm-cm and myocardial tissue resistivity of about 500 ohm-cm. Alternatively, the fluid can be a hypertonic potassium chloride solution. This medium, while promoting the desired ionic transfer, requires closer monitoring of the rate at which ionic transport occurs through themicropores28, to prevent potassium overload. When hypertonic potassium chloride solution is used, it is preferred to keep the ionic transport rate below about 1 mEq/min.
• Due largely to mass concentration differentials across themicropores28, ions in the conductive fluid will pass into the pores because of concentration differential-driven diffusion. Ion diffusion through themicropores28 will continue as long as a concentration gradient is maintained across thetherapeutic element14. The ions contained in themicropores28 provide the means to conduct current across thetherapeutic element14. When RF energy is conveyed from a RF power supply and control apparatus to theelectrode32, electric current is carried by the ions within themicropores28. The RF currents provided by the ions result in no net diffusion of ions, as would occur if a DC voltage were applied, although the ions do move slightly back and forth during the RF frequency application. This ionic movement (and current flow) in response to the applied RF field does not require perfusion of fluid through themicropores28. The ions convey RF energy through themicropores28 into tissue to a return electrode, which is typically an external patch electrode (forming a unipolar arrangement). Alternatively, the transmitted energy can pass through tissue to an adjacent electrode (forming a bipolar arrangement). The RF energy heats tissue (mostly ohmically) to coagulate the tissue and form a lesion.
• The temperature of the fluid is preferably monitored for power control purposes. To that end, athermistor34 may be mounted within the exemplarytherapeutic element14. Other temperature sensing devices, such as a thermocouple and reference thermocouple arrangement, may be employed in place of or in addition to thethermistor34. As illustrated for example inFIGS. 1-3,6 and7, theelectrode32 andthermistor34 are respectively connected to anelectrical connector36 in thehandle16 byconductors38 and40 which extend through theshaft12. Theprobe10 may be connected to a suitable RF power supply andcontrol apparatus41 by aconnector43 that mates with theelectrical connector36. Thehandle16 is provided with anopening42 for this purpose.
• Theexemplary probe10 may operate using a relatively simple control scheme wherein lesions are formed by supplying power to theelectrode32 at a predetermined level for a predetermined period of time. When forming pulmonary vein lesions, for example, about 35 watts for a period of about 120 seconds is preferred. Should the temperature within the inflatabletherapeutic element14 exceed 90° C., power will be cut off by thecontrol apparatus41.
• Accurate placement of thetherapeutic element14, particularly theporous region26, is also important and color may be used to make it easier for the physician to accurately position the therapeutic element. Theporous region26 may be one color while thenon-porous regions30 may be another color. Alternatively, or in addition, theporous region26 may be relatively clear and thenon-porous regions30 may be relatively opaque. These properties may also be reversed. In one exemplary implementation, theporous region26 may be substantially clear and colorless, while thenon-porous regions30 may be a relatively opaque blue color. This arrangement results in theporous region26 being a clear, colorless ring that is readily visible to the physician.
• The exemplarytherapeutic element14 is provided with a stabilizing structure44 (FIG. 3). The stabilizingstructure44 preferably includes a flexible, non-conductivetubular member46 and atip member48 on the distal end of the tubular member. The flexibility of thetubular member46, which supports theelectrode32 andthermistor34 and also provides passage for theconductors38 and40, prevents tissue perforation.Tip member48 includes a blunt distal surface that prevents tissue perforation. During assembly, the proximal end of thetubular member46 may be secured within the distal end of theshaft12 with a suitable adhesive material50 (such as cyanoacrylate) in the manner illustrated inFIG. 5.
• The exemplarytherapeutic element14 illustrated inFIG. 3 is molded such that the inner diameter of itsproximal end52 closely corresponds to the outer diameter of theshaft12 and the inner diameter of itsdistal end54 closely corresponds to the outer diameter oftip member48. Thepolymer coating20 may be removed from the distal tip of theshaft12 prior to assembly (as shown) or left in place and the therapeutic elementproximal end52 positioned thereover. Cyanoacrylate or another suitable adhesive material may be used to secure the therapeutic element proximal anddistal ends52 and54 in place and provide fluid tight seals.
• With respect to materials, theporous region26 is preferably formed from regenerated cellulose or a microporous elastic polymer. Hydro-Fluoro M material is another exemplary material. Materials such as nylons (with a softening temperature above 100° C.), PTFE, PEI and PEEK that have micropores created through the use of lasers, electrostatic discharge, ion beam bombardment or other processes may also be used. Such materials would preferably include a hydrophilic coating. The micropores should be about 1 to 5 μm in diameter and occupy about 1% of the surface area of theporous region26. A slightly larger pore diameter may be employed. Because the larger pore diameter would result in significant fluid transfer through the porous region, a saline solution having a sodium chloride concentration of about 0.9% weight by volume is preferred.
• The non-porous regions are preferably formed from relatively elastic materials such as silicone and polyisoprene. However, other less elastic materials, such as Nylon®, Pebax®, polyethylene, polyesterurethane and polyester, may also be used. Here, the inflatabletherapeutic element14 may be provided with creased regions that facilitate the collapse of the porous electrode.
• Additional information and examples of expandable and collapsible bodies are disclosed in U.S. patent application Ser. No. 08/984,414, entitled “Devices and Methods for Creating Lesions in Endocardial and Surrounding Tissue to Isolate Arrhythmia Substrates,” U.S. Pat. No. 5,368,591, and U.S. Pat. No. 5,961,513, each of which is incorporated herein by reference.
• Thetherapeutic element14 will typically be filled with conductive fluid prior to insertion of thesurgical probe10 into the patient. As illustrated for example inFIGS. 2, 5,6 and7, the conductive fluid is supplied under pressure to the inflatabletherapeutic element14 by way of aninfusion lumen56. The fluid exits thetherapeutic element14 by way of aventilation lumen58. The infusion andventilation lumens56 and58 extend from the distal end of theshaft12 and through a pair ofapertures60 and62 in thehandle16. The proximal ends of the infusion andventilation lumens56 and58 are provided with on-offvalves64 and66, which may be connected to the infusion andventilation lines68 and70 of afluid supply device72 such as, for example, an infusion pump capable of variable flow rates.
• In a preferred implementation, the conductive fluid is continuously infused and ventilated (at a rate of about 4-8 mils/minute for atherapeutic element14 that is about 1.5 cm in diameter). Thus, in addition to inflating thetherapeutic element14 and providing a conductive path from theelectrode32 to the tissue, the fluid cools the therapeutic element so that heat is only generated within the tissue by virtue of the passage of current therethrough.
• The pressure of the fluid supplied by thefluid supply device72 within thetherapeutic element14 should be relatively low (less than 20 psi) and may be varied by the fluid supply device in accordance with the desired level of inflation, strength of materials used and the desired degree of flexibility. The pressure, which is a function of the fluid flow rate, may be increased by increasing the fluid flow rate and decreased by decreasing the fluid flow rate. The desired pressure may be input into thefluid supply device72 and pressure regulation may be performed automatically by a controller within the fluid supply device which varies the flow rate as appropriate. Alternatively, the flow rate (and pressure) may be varied manually by the physician.
• Pressure within thetherapeutic element14 may be monitored in a variety of ways. For example, flow through the infusion andventilation lumens56 and58 may be cut off for a brief period (about 1 second) so that the fluid pressure can be measured by apressure sensor74 associated with the fluid supply device72 (as shown) or with one of thevalves64 and66. Alternatively, a pressure sensor lumen (not shown) that is filled with non-flowing fluid and extends from the interior of thetherapeutic element14 to thepressure sensor74 associated with thefluid supply device72, or to a pressure sensor associated with one of thevalves64 and66, may be used without cutting off the fluid flow.
• Varying the level of pressure within thetherapeutic element14 allows the physician to achieve the appropriate level of tissue contact, even when theshaft14 is not perfectly perpendicular to the target tissue area and when the target tissue area is somewhat uneven. For example, a stiffer therapeutic element14 (which distorts the tissue) would be preferred when the pulmonary vein ostium is relatively circular and when the ostium tissue is relatively healthy and pliable. A more flexible therapeutic element14 (which conforms to the tissue) would be preferred when the ostium is not circular and the ostium tissue is relatively calcified and rigid due to disease. The ability to vary the stiffness allows the physician to easily form a lesion that extends completely around the pulmonary vein or other bodily orifice by simply inserting the distal portion of theprobe10 into the patient, positioning thetherapeutic element14 in or around the bodily orifice, and applying power.
• The present inventions are, of course, applicable to therapies in areas other than the treatment of atrial fibrillation. One such therapy is the treatment of tumors, such as the cancerous tumors associated with breast cancer and liver cancer. One example of a surgical probe that is well suited for the treatment of tumors is illustrated inFIG. 8 and generally represented byreference numeral76.Surgical probe76 is substantially identical to theprobe10 illustrated inFIGS. 1-7. Here, however, the probe includes atherapeutic element78 that is formed from the same material asmicroporous region26 and is entirely covered withmicropores28. Although the size and shape will vary in accordance with the intended application, the exemplarytherapeutic element78 is approximately 5 mm to 50 mm in length and has a diameter of about 10 mm to 40 mm when inflated.
• The exemplarysurgical probe76 illustrated inFIG. 8 may be introduced to a target location, such as within a cancerous tumor, using a variety of techniques. Such techniques include laparoscopic techniques where the probe will be introduced with a trocar, radially expandable port, or step trocar expandable port. Thetherapeutic element78 should be deflated during the introduction process. Once thetherapeutic element78 is at the target location, it may be inflated and the tissue coagulated in the manner described above. Thetherapeutic element78 will be deflated and removed from the patient by way of the trocar, radially expandable port, or step trocar expandable port when the coagulation procedure is complete.
• The exemplarytherapeutic element78, as well as the other therapeutic elements described below that are intended to be expanded within the tissue of solid organ tissue or expanded within other tissue (seeFIGS. 9, 10 and12-16), may include larger pores than therapeutic elements that are expanded prior to use or expanded within a hollow region inside an organ or other portion of the body. Pore sizes up to 0.1 mm are acceptable. The larger pore sizes may be used because the tight fit between the tissue and the inflated therapeutic element that results from the inflation of the therapeutic element within solid tissue increases the effective flow resistance through thepores28. Additionally, the small amount of electrically conductive fluid leakage that may be associated with the use of larger pores will decrease ohmic losses and allow power to be increased without tissue charring and vaporization.
• Although its uses are not so limited, the exemplarysurgical probe80 illustrated inFIGS. 9 and 10 is also particularly well suited for treating tumors.Surgical probe80 includes ahollow needle82, a movabletherapeutic assembly84 that consists of ashaft12′ and atherapeutic element78′, and amovable stylet86 that protects the therapeutic element. Thetherapeutic assembly84 andstylet86 may be independently moved proximally and distally relative to thehollow needle82 withslidable knobs88 and90 mounted on thehandle16′.
• Surgical probe80 may be introduced into the patient through a trocar or any appropriate port and thehollow needle82 used to pierce through tissue and enter a target location such as a tumor. Thehollow needle82 may, alternatively, be used to introduce thesurgical probe80 into the patient as well as to pierce through tissue and enter the target location. In either case, once within the tumor or other target location, thehollow needle82 andstylet86 may be withdrawn while thetherapeutic assembly84 is held in place so that thetherapeutic element78′ will remain within the target location. Thetherapeutic element78′ may then be inflated and the tissue associated with the target location coagulated in the manner described above. Once the coagulation procedure is complete, thetherapeutic element78′ will be deflated so that thestylet86 can be slid over the therapeutic element. Both will then be pulled back into thehollow needle82 so that theprobe80 can be removed from the patient.
• The size, shapes and materials used to form thehollow needle82,therapeutic assembly84 andstylet86 will vary in accordance with the intended application.
• With respect to tumor treatment, the exemplaryhollow needle82 is preferably linear, is between about 1.3 cm and 7.6 cm in length, and has an outer diameter that is between about 2.0 mm and 6.4 mm and an inner diameter that is between about 1.5 mm and 5.8 mm. Suitable materials for thehollow needle82, which is preferably either straight or has a preset curvature, include stainless steel and Nitinol. Theshaft12′ is preferably straight (although it can have a curvature) and rigid (although it may be malleable) and the stiffness is uniform from one end to the other. Suitable materials include stainless steel, Nitinol and rigid polymers. The diameter is preferably between about 0.6 mm and 4.6 mm. The exemplarytherapeutic element78′ is approximately 19 mm to 38 mm in length, a diameter of about 5 mm and 40 mm when inflated, with a wall thickness of about 0.025 mm to 0.250 mm. Thestylet86 may be formed from materials such as stainless steel and Nitinol and preferably has an outer diameter that is between about 1.4 mm and 5.7 mm and an inner diameter that is between about 1.1 mm and 5.2 mm.
• Turning toFIG. 11, surgical probes in accordance with other embodiments of the present inventions, which are otherwise substantially identical to theprobe10 illustrated inFIGS. 1-7, may include a heated inflatabletherapeutic element92 in place of the poroustherapeutic element14. The exemplarytherapeutic element92, which is supported on the distal end of theshaft12 in essentially the same manner astherapeutic element14, can be inflated with water, hypertonic saline solution, or other biocompatible fluids. The fluid may be supplied under pressure to thetherapeutic element92 by thefluid supply device72 in the manner described above. The pressure should be relatively low (less than 20 psi) and will vary in accordance with the desired level of inflation, strength of materials used and the desired level of flexibility. The fluid will preferably be continuously infused and ventilated for cooling purposes. Alternatively, the fluid may instead fill the therapeutic element, remain there to be heated, and then be ventilated after the lesion formation procedure has been completed.
• A fluid heating element is located within thetherapeutic element92. The fluid heating element is preferably an electrode (not shown) that may be formed from metals such as platinum, gold and stainless steel and mounted on thesupport structure44. A bi-polar pair of electrodes may, alternatively, be used to transmit power through a conductive fluid, such as isotonic saline solution, to generate heat. The temperature of the fluid may be heated to about 90° C., thereby raising the temperature of the exterior of thetherapeutic element92 to approximately the same temperature for tissue coagulation. It should be noted, however, that thetherapeutic element92 tends to produce relatively superficial lesions.
• Suitable materials for the exemplarytherapeutic element92 include relatively elastic thermally conductive biocompatible materials such as silicone and polyisoprene. Other less elastic materials, such as Nylon®, Pebax®, polyethylene and polyester, may also be used. Here, thetherapeutic element92 will have to be formed with fold lines. A temperature sensing element may also be provided. The heating electrode and temperature sensing element will be connected to theelectrical connector36 in thehandle18 by electrical conductors in the manner described above. Suitable power supply and control devices, which control power to based on a sensed temperature, are disclosed in U.S. Pat. Nos. 5,456,682, 5,582,609 and 5,755,715.
• The exemplarytherapeutic element92 may also be used in conjunction with the surgical probes illustrated inFIGS. 8-10.
• As illustrated for example inFIGS. 12-16, asurgical probe94 in accordance with a preferred embodiment of a present invention includes a plurality oftissue penetrating needles96 that may be advanced outwardly from, and retracted back into, the distal end of ashaft12 with aslidable knob98. The number ofneedles96, which may be glued, clamped or otherwise secured to theslidable knob98, preferably ranges from 1 to 25. Each of theneedles96 includes amain body100, a sharpenedtip102 and an inflatable poroustherapeutic element104 withmicropores28. The materials used to form thetherapeutic element104, as well as the conductive fluid used therewith, are the same as those described above with respect to theporous region26. Hydro-Fluoro M material may also be used. When inflated, afluid circulation space106 is defined between themain body100 and thetherapeutic element104. Anelectrode32 and athermistor34, which are positioned on themain body100 within thespace106, are connected to theelectrical connector36 byconductors38 and40.
• Although other configurations may be employed, the exemplarytissue penetrating needles96 preferably have the preset curvature illustrated inFIG. 13 and will assume this curvature when they are advanced outwardly from the distal end of theshaft12. To that end, suitable shape-memory materials for theneedles96 include stainless steel and Nitinol. It should be noted that theneedles96 do not each have to have the same curvatures or to even be curved at all. Theneedles96 are preferably about 0.25 mm to 1.25 mm in diameter and the curved region is about 2.5 cm in length, while the diameter of the poroustherapeutic element104 is about 1 mm to 10 mm when inflated and the thickness of the porous material is about 0.025 mm to 0.250 mm. In an implementation with six (6) needles96, theprobe94 would produce a lesion that is about 2 cm to 3 cm deep and about 2 cm to 3 cm in diameter.
• The exemplarytissue penetrating needles96 each include infusion and ventilation sub-lumens108 and110 with distal ends that respectively terminate at infusion andventilation apertures112 and114 within thetherapeutic element104. The proximal ends of the infusion and ventilation sub-lumens108 and110 in each of theneedles96 are connected to theinfusion lumen56 andventilation lumen58 by a pair of suitable plumbing junctions located within thehandle16″.
• It should be noted that, because theneedles96 are moved back and forth relative to the12, theconductors38 and40 andsub-lumens108 and110 should include some slack within thehandle16″.
• In addition to conducting energy, the conductive fluid may be continuously infused and ventilated through thetherapeutic elements104 such that it draws heat away from the therapeutic element and the tissue adjacent thereto. This results in the formation of relatively deep, large volume lesions (as compared to devices with conventional needle electrodes) without charring and coagulation. Cooling thetherapeutic elements104 and the adjacent tissue also greatly reduces the amount of time required to form a large volume lesion (as compared to devices with conventional needle electrodes) because higher power is provided when heat is removed from the area adjacent to theneedles96.
• Each of the devices described above may be operated in both low voltage modes and high voltage modes. In an exemplary low voltage mode, RF energy will be applied that has a waveform shape and duration that electrically heats and kills tissue in the target region. A typical lesion within the heart could formed by delivering approximately 150 watts of power for about 10 to 120 seconds at a radio frequency of 500 kHz. Applied voltages may range from 60 to 100 volts rms.
• Turning to high voltage modes, high voltage energy pulses can be used to kill, coagulate or otherwise modify tissue in at least three ways. For example, the creation of high voltage gradients within the tissue dielectrically breaks down tissue structures. In addition, ohmically heating tissue will coagulate tissue structures, while ohmically heating to very high temperatures will vaporize tissue.
• With respect to killing tissue through the dielectric breakdown of cell membranes, relatively short (about 0.1 msec) high voltage (about 400 to 4000 volts with 1000 volts being preferred) RF pulses that result in voltage gradients at or above 500 volts/cm being induced in tissue will accomplish the desired result. Turning to heating, a high voltage RF pulse (about 500 to 1200 volts in magnitude and about 50 to 100 msec in duration) delivers relatively high power to tissue, thereby enabling very rapid heating. Because the tissue is heated rapidly, there is essentially no convective heat loss during power application. Tissue vaporization can be performed through the use of high voltage energy pulses with a pulse duration of about 250 msec to 1 sec. Additional information concerning high and low voltage tissue modification is provided in U.S. Pat. No. 6,023,638, which is incorporated herein by reference.
• Although the present inventions have been described in terms of the preferred embodiments above, numerous modifications and/or additions to the above-described preferred embodiments would be readily apparent to one skilled in the art. It is intended that the scope of the present inventions extend to all such modifications and/or additions and that the scope of the present inventions is limited solely by the claims set forth below.

Claims (8)

1-28. (canceled)

29. A method of forming a lesion around a body orifice, comprising the steps of:

providing a surgical probe including a relatively short shaft defining a distal portion and a proximal portion and an inflatable therapeutic element associated with the distal portion of the shaft;

inflating the inflatable therapeutic element to a predetermined pressure;

positioning the inflatable therapeutic element adjacent to the body orifice; and

forming a lesion around the body orifice with the inflatable therapeutic element.

30. A method as claimed inclaim 29, wherein the step of positioning the inflatable therapeutic element comprises positioning the inflatable therapeutic element adjacent to a pulmonary vein.

31. A method as claimed inclaim 29, wherein the step of forming a lesion around the body orifice comprises transmitting energy from the inflatable therapeutic element to tissue associated with the body orifice.

32. A method as claimed inclaim 29, wherein the step of forming a lesion around the body orifice comprises heating tissue associated with the body orifice with the inflatable therapeutic element.

33. (canceled)

34. A method of coagulating tumor tissue, comprising the steps of:

inserting an inflatable therapeutic element into the tumor; and

coagulating tissue with the inflatable therapeutic element.

35. A method as claimed inclaim 34, wherein the step of inserting an inflatable therapeutic element into the tumor comprises the steps of inserting the inflatable therapeutic element into the tumor in a deflated state and inflating the inflatable therapeutic element within the tumor.

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