Ablation of hard-to-access region

Abstract

To ablate tissue.SOLUTION: An apparatus includes a shaft and an inflatable balloon coupled to a distal end of the shaft. The balloon includes a proximal portion electrically conducting over at least half of a proximal-portion circumference of the proximal portion, a distal portion electrically conducting over at least half of a distal-portion circumference of the distal portion, and an electrically insulating middle portion that insulates the proximal portion from the distal portion. Other embodiments are also described.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to tissue ablation. [Background technology]

[0002] The ligament of Marshall (LOM), located on the epicardium between the left atrial appendage and the left pulmonary veins, is a frequent source of paroxysmal atrial fibrillation.

[0003] Radiofrequency (RF) ablation and irreversible electroporation (IRE) are the primary therapies for ablating cardiac tissue, for example, to treat atrial fibrillation.

[0004] U.S. Pat. No. 9,655,677 describes a cardiac tissue ablation catheter comprising an inflatable, flexible, toroidal or spherical balloon disposed at a distal region of an elongate member; a flexible circuit carried by the outer surface of the balloon, the flexible circuit including a plurality of flexible branch portions conforming to the radially outer surface of the balloon, each of the plurality of flexible branch portions including a substrate, a conductive trace carried by the substrate, and an ablation electrode carried by the substrate, the ablation electrode being in electrical communication with the conductive trace; and an elongate shaft extending within the elongate member and extending from a proximal region of the inflatable balloon to a distal region of the inflatable balloon, the distal region of the elongate shaft being directly or indirectly secured to the distal region of the inflatable balloon. Summary of the Invention [Means for solving the problem]

[0005] According to some embodiments of the present invention, there is provided a device including a shaft and an inflatable balloon coupled to a distal end of the shaft, the balloon including a proximal portion that is electrically conductive over at least half of a circumference of the proximal portion of the proximal portion, a distal portion that is electrically conductive over at least half of a circumference of the distal portion of the distal portion, and an electrically insulating intermediate portion that insulates the proximal portion from the distal portion.

[0006] In some embodiments, the length of the balloon is 2 to 20 times greater than the maximum cross-sectional diameter of the balloon.

[0007] In some embodiments, the balloon is shaped to define a plurality of openings through the wall of the balloon.

[0008] In some embodiments, the balloon further comprises an atraumatic tip disposed distally to the electrically conductive distal portion.

[0009] In some embodiments, the distal end of the shaft protrudes from the balloon.

[0010] In some embodiments, the electrically insulating intermediate portion does not have any conductive elements disposed thereon.

[0011] According to some embodiments of the present invention, there is further provided a probe including a guidewire configured to access tissue of a human subject by traversing a lumen of the tissue. The probe further includes a tube sized to access and enter the lumen while being passed over the guidewire, the tube being shaped to define a lumen. The probe further includes a plurality of expandable electrodes configured to traverse the lumen and expand distally relative to a distal end of the tube following traversal of the lumen to deliver ablation energy to the tissue by current flowing between the electrodes, at least one of the expanding electrodes contacting the tissue.

[0012] In some embodiments, the expandable electrodes are configured to deliver ablation energy without causing permanent deformation to any of the electrodes.

[0013] In some embodiments, the probe further comprises a shaft having a distal end connected to the expandable electrode.

[0014] In some embodiments, the shaft includes at least one conductor configured to conduct electrical current to the electrode without permanently damaging it.

[0015] In some embodiments, the expandable electrode includes an electrically conductive proximal portion of the inflatable balloon and an electrically conductive distal portion of the inflatable balloon, which are configured to expand upon inflation of the inflatable balloon.

[0016] In some embodiments, the tissue comprises a ligament of Marshall.

[0017] A method for ablating tissue in a human subject is further provided in accordance with one embodiment of the present invention. The method includes inserting a guidewire into a lumen of the human subject. The method further includes threading a tube over the guidewire, the tube being sized to pass through the lumen such that a distal end of the tube is proximate to a target region to be ablated. The method further includes traversing a plurality of expandable electrodes through the tube after threading the tube over the guidewire. Following traversing the plurality of expandable electrodes through the tube, the method further includes expanding the expandable electrodes distally relative to the distal end of the tube such that at least one of the expandable electrodes contacts the target region to be ablated. The method further includes transmitting electrical energy to the contacted target region by passing an electrical current between the expandable electrodes to ablate the target region.

[0018] In some embodiments, transmitting the electrical energy includes transmitting the electrical energy without causing permanent deformation to any of the expandable electrodes.

[0019] In some embodiments, expanding the expandable electrode distally relative to the distal end of the tube comprises expanding the expandable electrode by pushing the expandable electrode out of the distal end of the tube.

[0020] In some embodiments, the expandable electrode is connected to a distal end of a shaft, and traversing the expandable electrode through the vessel comprises traversing the expandable electrode through the vessel using the shaft.

[0021] In some embodiments, the shaft includes at least one conductor configured to conduct electrical current to the electrode without permanently damaging it.

[0022] In some embodiments, the tissue comprises a ligament of Marshall.

[0023] In some embodiments, transmitting electrical energy comprises transmitting electrical energy to irreversibly electroporate the target region.

[0024] In some embodiments, the expandable electrode includes an inflatable balloon conductive proximal portion and an inflatable balloon conductive distal portion; Expanding the expandable electrode includes expanding the expandable electrode by inflating a balloon.

[0025] In some embodiments, the length of the balloon is 2 to 20 times greater than the maximum cross-sectional diameter of the balloon.

[0026] In some embodiments, the balloon is shaped to define a plurality of openings through the wall of the balloon, and the method further includes passing a fluid through the openings while transmitting the electrical energy.

[0027] The invention is more fully understood when considered in conjunction with the following detailed description of the invention, in which: [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a schematic diagram of a medical system, according to one embodiment of the present invention. [Figure 2] 1 is a schematic diagram of elements of a medical probe used in the system, according to one embodiment of the present invention. [Figure 3] FIG. 1 is a flow diagram of the steps used to ablate tissue using a medical probe, according to one embodiment of the present invention. [Figure 4A] 2 is a schematic diagram of some of the steps of the flow diagram according to one embodiment of the present invention. [Figure 4B] 2 is a schematic diagram of some of the steps of the flow diagram according to one embodiment of the present invention. [Figure 4C] 2 is a schematic diagram of some of the steps of the flow diagram according to one embodiment of the present invention. [Figure 4D] 2 is a schematic diagram of some of the steps of the flow diagram according to one embodiment of the present invention. [Figure 5] 1 is a schematic diagram of a medical probe, according to some embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] Overview Many regions of the heart are relatively easily accessed endocardially and are therefore suitable for ablation with conventional catheters, such as focal or balloon catheters. However, there are certain regions of the heart, such as the ligament of Marshall, that are difficult to access endocardially because the intracardiac pathways can be tortuous and include one or more relatively sharp bends that conventional catheters cannot traverse. While these regions may occasionally be accessed epicardially, endocardial access is preferred.

[0030] To address this challenge, the inventors have developed devices and methods for endocardial access to difficult-to-reach regions of a patient's anatomy. The ligament of Marshall is described herein as an example of one such region. This description may be adapted, mutatis mutandis, for other difficult-to-reach regions.

[0031] In one embodiment of the present invention, a medical probe includes three elements: a flexible guidewire, a tube configured to pass along the guidewire, and a shaft having one or more (typically two or more) expandable electrodes at the distal end of the shaft that can traverse the tube. In contrast to the conventional catheters described above, which cannot access hard-to-reach areas, this probe can access areas by virtue of its narrow width and flexibility.

[0032] The guidewire is navigated to the region targeted for ablation, and then the probe's tube is threaded along the guidewire until the distal end of the tube is proximate the target region. A shaft with expandable electrodes is then pushed into the tube until the expandable electrodes exit the distal end of the tube, at which point the electrodes expand so that at least one of them contacts the target region (the tube thus guides the expandable electrodes along a desired path to the target region). The expanded electrodes may then be used to ablate the target region, typically by passing a bipolar current between the electrodes.

[0033] Advantageously, the electrode is large enough to carry the ablation current without irreversible damage, and the shaft is large enough to support a conductor that will not be damaged by the current transmission.

[0034] In some embodiments, the electrodes are self-expanding because they are formed of a shape-memory material. In other embodiments, the electrodes are actively expanded. For example, an inflatable balloon may be coupled to the distal end of the shaft, and the surface of the balloon may be coated with a suitable metallic material to define two electrodes. The balloon may be inflated to expand the electrodes.

[0035] System Description Figure 1 is a schematic diagram of a medical system 20 including a medical probe 22 and a control console 24, and Figure 2 is a schematic diagram of elements of the medical probe, according to one embodiment of the present invention. The medical system 20 may be based, for example, on the CARTO® system manufactured by Biosense Webster Inc. (31 Technology Drive, Irvine, CA 92618 USA). The probe 22 is used as a catheter and is also referred to herein as a catheter 22.

[0036] 1 shows a physician 36 controlling the probe 22 using a handle 80. In the embodiment described below, the medical probe 22 is used to ablate tissue within a heart 28 of a patient 30 (also referred to herein as a subject). Typically, the probe 22 is used to ablate difficult-to-access elements of the heart, and as an example, ablation of a portion of the ligament of Marshall of the heart 28 is described herein. However, it should be understood that the medical probe 22 may be used, mutatis mutandis, for other therapeutic and / or diagnostic purposes in the heart or other body organs.

[0037] As shown in FIG. 2, the probe 22 includes a flexible guidewire 26, a flexible tube 32, and a flexible shaft 54.

[0038] Guidewire 26 is typically curved at its distal end, as shown, and includes a position sensor 38 at its distal end, which typically includes at least one coil. Alternatively or additionally, guidewire 26 typically includes at least one electrode 74 at its distal end, which may also be used for position sensing. In one embodiment, guidewire 26 is formed as a stainless steel coil having a diameter of approximately 325 micrometers, with the conductors of sensor 38 and / or electrode 74 traversing the lumen of the coil.

[0039] The flexible tube 32 also typically has a position sensor 34 at its distal end, which typically comprises at least one coil. Alternatively or additionally, the tube 32 typically has at least one electrode 76 at its distal end, which may be used for position sensing. The tube 32 is sized to have an inner diameter that allows it to be threaded over the guidewire 26 and an outer diameter of approximately 1 mm, allowing it to enter a vein or other body cavity approximately 1 mm in diameter. The tube 32 may be composed of any stable, biocompatible plastic that can be formed to these dimensions. The conductors for the sensor 34 and / or electrode 76 may be formed within the wall of the tube 32.

[0040] The flexible shaft 54 ​​is typically formed as a braided tube (e.g., made of polyimide), the braid resisting the shaft's tendency to kink. At the distal end of the shaft are one or more (typically two or more) expandable electrodes 64. The electrodes 64 are configured to be large enough to transmit ablation energy to tissue in contact with the electrodes without permanently deforming the electrodes. Similarly, conductors connected to the electrodes configured to transmit ablation energy traverse the shaft and are large enough to transmit the ablation energy without permanently deforming the shaft.

[0041] Each of the electrodes 64 is described herein as “expandable” in that, upon exiting the tube 32, the electrode may expand from a radially compressed configuration (as it is considered to be in this configuration while within the tube 32) to a radially expanded configuration. In some embodiments, each electrode is formed of a shape memory material, such as nitinol (optionally coated with a biocompatible material, such as gold), such that the electrode expands due to a shape memory effect, i.e., the electrode is self-expanding. In other embodiments, the electrode is actively expanded by the application of electrical and / or mechanical energy. Such energy may be applied by the physician 36 or by the processor 44 (described below), optionally in response to input from the physician. In the context of this application, including the claims, the term “expandable electrode” includes both self-expanding and non-self-expanding electrodes.

[0042] In general, each of the electrodes 64 may have any suitable shape. For example, as shown in FIG. 2, each electrode may have a helical or spiral configuration. Alternatively, each electrode may include a basket of circumferentially distributed spines disposed over the shaft. In such embodiments, the electrodes may be self-expanding, or expansion may be achieved by pulling a pullwire coupled to the basket to retract the distal end of the basket toward the proximal end of the basket. In yet other embodiments, as described below with reference to FIG. 5, each of the electrodes 64 includes an inflatable balloon-coated portion such that the electrode expands upon inflation of the balloon.

[0043] 1, the control console 24 is connected via a cable 40 to body surface electrodes, which typically comprise adhesive skin patches 42 that are applied to the patient 30. The control console 24 also includes a processor 44 coupled to several modules, which include software and / or hardware components, the details and functions of which are described below.

[0044] Processor 44 determines the location coordinates, i.e., position and orientation coordinates, of the distal ends of guidewire 26 and tube 32 based on signals received from sensors 38 and 34, respectively, via electromagnetic (EM) tracking module 88. The sensors are responsive to magnetic fields and generate signals transmitted by alternating magnetic field emitters 78 positioned beneath patient 30 that traverse the sensors.

[0045] Alternatively or additionally, processor 44, in conjunction with current tracking module 46, determines position coordinates of the distal end of guidewire 26 and / or tube 32 within heart 28 based on the impedance and / or current measured between adhesive skin patch 42 and electrodes 74 and 76. Instead of, or in addition to being used as location sensors during a medical procedure, electrodes 74 and 76 may perform other tasks, such as measuring electrical activity of heart 28.

[0046] The processor 44 may include a real-time noise reduction circuit 50, typically configured as a field programmable gate array (FPGA), followed by an analog-to-digital (A / D) signal conversion integrated circuit 52. The processor may pass signals from the A / D circuit 52 to another processor and / or may be programmed to determine the position coordinates referred to above.

[0047] Impedance and current based position tracking techniques are described, for example, in U.S. Patent Nos. 5,983,126, 6,456,864, and 5,944,022. Electromagnetic position tracking techniques are described, for example, in U.S. Patent Nos. 5,391,199, 6,690,963, and 6,892,091. The position sensing methods described hereinabove are implemented in the CARTO® system and are described in detail in the above-cited patents, the disclosures of each of which are incorporated by reference into this patent application.

[0048] Prior to inserting the elements of probe 22 into patient 30, processor 44 acquires an electroanatomical map 56 of heart 28. Typically, the data for the map is acquired using a probe other than probe 22, such as a focal catheter configured to acquire signals from regions of the heart chamber tracked by module 46 and contacted by the catheter. Typically, but not necessarily, processor 44 uses the signals to determine local activation times (LATs) of the heart chambers and incorporates the LATs into map 56. Map 56 is stored in memory 60 accessible by processor 44, and during a procedure, processor 44 can present map 56 to physician 36 on display 58.

[0049] During a procedure using the probe 22, the processor 44 may overlay an icon representing the location of the distal tip on the map 56 to allow the physician 36 to track the distal tip.

[0050] Memory 60 may comprise any suitable volatile and / or non-volatile memory, such as random access memory or a hard disk drive. In some embodiments, physician 36 may manipulate map 56 using one or more input devices 62. In alternative embodiments, display 58 may comprise a touch screen that may be configured to receive input from physician 36 in addition to presenting map 56.

[0051] Control module 24 also includes an ablation module 66. Ablation module 66 is configured to monitor and control ablation parameters, such as the level and duration of ablation power (e.g., radio frequency (RF) energy) delivered from ablation module 66 to electrodes 64, and module 66 typically includes a generator 86, such as an RF generator, for this purpose.

[0052] Figure 3 is a flow diagram of a process used to ablate tissue using probe 22, and Figures 4A-4D are schematic diagrams of portions of the process, according to one embodiment of the present invention. Figures 4A-4D schematically illustrate the coronary sinus 150 of heart 28, the ligament of Marshall (LOM) 154 connecting to the coronary sinus, and a vein 158 passing through the LOM. For the purposes of the following discussion, it will be assumed, by way of example, that a target region 162 of LOM 154 is to be ablated.

[0053] In a first step 100, the physician 36 inserts the guidewire 26 into the subject and then navigates the guidewire to the heart 28. Within the heart, the guidewire is navigated through the coronary veins 150 and into the ligament of Marshall's vein 158 until the distal end of the guidewire is distal to the target region 162 (e.g., within 10 mm of the target region). The physician is typically assisted in navigation by the processor 44, which uses signals from the sensors 38 or from the electrodes 74 to display an icon on the map 56 representing the location of the distal end of the guidewire. Alternatively or additionally, the physician 36 may perform navigation using fluoroscopy.

[0054] It will be appreciated that intracardiac navigation to difficult-to-access sites such as the LOM 154 is complicated because the guidewire 26 must bend around one or more sharp angles. For example, to reach the LOM, the guidewire may need to pass through the inferior vena cava, the right atrium, and the coronary sinus. Complex navigation is facilitated by the guidewire 26 being made very thin yet configured to be flexible without kinking.

[0055] FIG. 4A illustrates the final stage of process 100, showing guidewire 26 within LOM vein 158.

[0056] Once the physician 36 has navigated the distal end of the guidewire sufficiently to be distal to the target region 162, a vessel threading step 104 involves the physician threading the vessel 32 along the guidewire until the distal end of the vessel is proximate the target region 162. To assist the physician in accurately placing the distal end of the vessel, the processor 44 may use signals from the sensors 34 or electrodes 76 to display a representation of the vessel distal end on the map 56. Alternatively or additionally, the physician may use fluoroscopy to accurately locate the distal end of the vessel.

[0057] The final stage of step 104 is shown in Figure 4B, which shows the distal end of tube 32 near target area 162.

[0058] In electrode traversal step 112, the physician inserts a shaft 54 ​​having at least one expandable electrode 64 connected to the shaft's distal end into the vessel 32. The electrode 64 may be compressed by the vessel wall but can still traverse the vessel when the physician pushes on the proximal end of the shaft.

[0059] The physician continues to push the proximal end of the shaft, thus continuing the lateral movement of the electrodes 64 through the vessel 32 until the electrodes exit the distal end of the vessel. Once exiting the distal end of the vessel, the electrodes may self-expand such that at least one of the electrodes contacts the target area 162. In other words, if the electrodes are self-expanding, the physician can expand the electrodes distally relative to the distal end of the vessel 32 simply by pushing the electrodes out of the distal end of the vessel. If the electrodes are not self-expanding, the electrodes may be expanded by performing an additional electrode expansion step, such as, for example, balloon inflation ( FIG. 5 ). The electrode expansion step may occur between the electrode lateral movement step 112 and the first retraction step 116 (described below) or between the first retraction step 116 and the ablation step 120.

[0060] In one embodiment of the present invention, the position of the electrode 64 relative to the target area 162 may be verified by the current tracking module 47 using the impedance and / or current between the electrode and the patch 42. Alternatively or additionally, the position of the electrode may be confirmed with fluoroscopy.

[0061] In a first retraction step 116, once the electrodes 64 emerge from the distal end of the tube and at least one of the electrodes is in contact with the target area 162, the physician partially retracts the tube 32, typically by pulling about 1 cm, so that its distal end is no longer close to the target area.

[0062] Figure 4C shows the shaft 54 ​​and expandable electrode 64 within the tube 32 before the electrode emerges from the distal end of the tube. Figure 4D shows the condition at the end of step 116, when the electrode 64 has emerged from the distal end of the tube 32 and expanded to contact the target area 162, and the distal end of the tube has been partially retracted.

[0063] In the ablation step 120, the physician operates the processor 44 and the ablation module 66 to supply current to the electrodes 64. If more than one electrode 64 is present, the supplied current may be bipolar, i.e., current may flow between the electrodes to deliver ablation energy to the tissue. Alternatively (e.g., if only one electrode 64 is present), the supplied ablation energy may be monopolar, i.e., current may be applied between one of the electrodes 64 and a return electrode (not shown) connected to the generator 86. The return electrode may be disposed outside the body of the patient 30. For example, the return electrode may include a patch coupled to the patient's body.

[0064] In some embodiments, RF current is supplied to the electrodes to perform RF ablation of tissue, or pulsed current may be supplied to perform irreversible electroporation (IRE) or pulsed field ablation (PFA).

[0065] In a second retraction step 124, once the physician has completed the ablation in step 120, the physician can advance the tube to the electrode, retract the electrode 64 into the tube, and then retract the combination of tube, shaft 54, and electrode 64 from the patient 30. In some embodiments, before retracting the electrode into the tube, the electrode may be compressed, for example, by deflating a balloon (FIG. 5). The guidewire may then be retracted.

[0066] 3 illustrates the ablation of one target region. However, embodiments of the present invention are not limited to the ablation of a single region, but rather may be used to ablate two or more separate regions during a single ablation procedure. For example, if there is a second target region closer to the coronary sinus than target region 162, as described in step 124, an electrode may be retracted into the tube, the combination may be moved adjacent to the second region, and the electrode may be pushed out of the distal end of the tube and expanded to contact the second region in preparation for ablation of that region.

[0067] Reference is now made to FIG. 5, which is a schematic illustration of a probe 22, according to some embodiments of the present invention.

[0068] In some embodiments, the probe 22 further comprises an inflatable balloon 68 coupled to the distal end of the shaft 54. The balloon 68 comprises an electrically conductive proximal portion 68p and an electrically conductive distal portion 68d, along with an electrically insulating intermediate portion 68m that insulates the proximal portion 68p from the distal portion 68d (typically, no electrodes or any other conductive elements are disposed on the electrically insulating intermediate portion 68m). The proximal and distal ends of the balloon, i.e., the proximal end of the proximal portion 68p and the distal end of the distal portion 68d, are joined to the shaft.

[0069] Balloon 68 is typically made of a polymer such as polyurethane, and each of the proximal and distal portions of the balloon further includes a conductive metal coating (e.g., comprising gold) coating the polymer (the coating is represented by a dotted hatch pattern in FIG. 5). Conductors (e.g., wires) traversing the shaft connect these metal coatings to generator 86 (FIG. 1).

[0070] To coat the proximal and distal portions of the polymer, the intermediate portion 68m may be shielded and the polymer may be placed in a plating bath. To facilitate plating, a charged seed layer (e.g., comprising silver, palladium, titanium tungsten, and / or titanium) may be deposited on the polymer prior to plating.

[0071] Typically, to increase contact with the target area, each of the proximal and distal portions of the balloon is electrically conductive over at least half of its circumference. For example, the aforementioned conductive metal coating may extend around the entire circumference of each of these portions. Alternatively, at least one of these portions may include multiple individual electrodes that collectively occupy at least half of the circumference of the portion. As a purely illustrative example, two electrodes may each span 150 degrees, with two 30-degree electrically insulating gaps separating the electrodes from each other. Such electrodes may be formed, for example, by placing an additional shield over the gap between the electrodes and performing the coating procedure as described above.

[0072] Typically, the balloon 68 is relatively elongated to facilitate contact with the target area 162 while being disposed within a narrow lumen, such as a vein 158 (FIGS. 4A-4D). For example, the length L of the balloon may be 2-20 times greater than the maximum cross-sectional diameter D of the balloon, and is typically 1-3 mm (typically, D is the diameter of the intermediate portion 68m, or at least the diameter of its axis; for example, the intermediate portion 68m may be of constant diameter D, with the proximal and distal portions of the balloon being of variable diameter such that the balloon reaches its minimum diameter at its proximal and distal ends).

[0073] In some embodiments, sensing electrodes and / or other sensors are coupled to intermediate section 68m and connected to console 24 (FIG. 1) via conductors (e.g., wires) that traverse the shaft. Such sensors may be used, for example, to obtain electrophysiological signals from tissue or to measure impedance.

[0074] In some embodiments, the balloon further comprises an atraumatic tip 72 disposed distally to the conductive distal portion. The atraumatic tip 72 is typically made of a relatively soft and compressible material such as polyurethane or polyether block amide (PEBA).

[0075] In some embodiments, the distal end of the shaft protrudes from the balloon, as shown in Figure 5. The distal end of the shaft may include an atraumatic tip 73, which may be made of polyurethane, PEBA, or any other suitable material. In other embodiments, particularly those in which the balloon includes an atraumatic tip 72, the shaft may terminate proximally to the distal end of the balloon.

[0076] The embodiment of probe 22 shown in Figure 5 is typically used as described above with reference to Figure 3, with the conductive proximal and distal portions of the balloon functioning as expandable electrodes 64 (Figure 2). Typically, current flows between the two conductive portions of the balloon; i.e., the ablation is bipolar.

[0077] Typically, the balloon is shaped to define a plurality of openings 70 through the wall of the balloon. A fluid delivery tube (not shown) configured to deliver a fluid, such as saline, from a pump (FIG. 1) in console 24 to the interior of the balloon passes through shaft 54. Fluid may flow through the fluid delivery tube and into the balloon to inflate the balloon (and subsequently maintain it in an inflated state during the ablation procedure). The flow of fluid through holes 70 may also help transfer heat from the tissue and prevent the patient's blood from clotting while electrical energy is being transferred to the tissue.

[0078] It will be understood by those skilled in the art that the present invention is not limited to what has been particularly shown and described herein. Rather, the scope of the embodiments of the present invention includes both combinations and subcombinations of the various features described herein, as well as variations and modifications of features that are not present in the prior art and that would occur to one skilled in the art upon reading the above description. Documents incorporated by reference into this patent application are considered to be part of this application, except that if any term is defined in these incorporated documents in a way that contradicts the definition given herein, either expressly or impliedly, then only the definition given herein shall be considered.

[0079] [Embodiment] (1) A device comprising: A shaft, an inflatable balloon coupled to a distal end of the shaft, the balloon comprising: a proximal portion that is electrically conductive over at least half of a circumference of the proximal portion; a distal portion that is electrically conductive over at least half of a circumference of the distal portion; a balloon; and an electrically insulating intermediate portion insulating the proximal portion from the distal portion. (2) The device of embodiment 1, wherein the length of the balloon is 2 to 20 times greater than the maximum cross-sectional diameter of the balloon. (3) The device of embodiment 1, wherein the balloon is shaped to define a plurality of openings through the wall of the balloon. (4) The device described in embodiment 1, wherein the balloon further comprises an atraumatic tip disposed distal to the conductive distal portion. (5) The device described in embodiment 1, wherein the distal end of the shaft protrudes from the balloon.

[0080] (6) The device of embodiment 1, wherein no conductive element is disposed on the electrically insulating intermediate portion. (7) A probe, a guidewire configured to access tissue of a human subject by traversing a lumen of said tissue; a tube sized to access and enter the lumen while being passed along the guidewire, the tube being shaped to define a lumen; A plurality of expandable electrodes, traverses the lumen; following traversal of the lumen, extending distally to a distal end of the tube; electrodes configured to transmit ablation energy to the tissue by current flowing between the electrodes while at least one of the extended electrodes is in contact with the tissue. (8) The probe described in embodiment 7, wherein the expandable electrodes are configured to transmit the ablation energy without causing permanent deformation to any of the electrodes. (9) The probe described in embodiment 7, further comprising a shaft having a distal end connected to the expandable electrode. (10) The probe of embodiment 9, wherein the shaft comprises at least one conductor configured to conduct the current to the electrode without permanently damaging it.

[0081] (11) The probe of embodiment 9, wherein the expandable electrode comprises a conductive proximal portion of the expandable balloon and a conductive distal portion of the expandable balloon configured to expand upon inflation of the expandable balloon. (12) The probe of embodiment 7, wherein the tissue comprises a Marshall ligament. (13) A method for ablating tissue in a human subject, comprising: inserting a guidewire into a lumen of the human subject; passing a tube over the guidewire, the tube sized to pass through the lumen such that a distal end of the tube is proximate to a target area to be ablated; passing the tube along the guidewire and then traversing a plurality of expandable electrodes through the tube; following traversing the expandable electrodes through the tube, expanding the expandable electrodes distally relative to the distal end of the tube such that at least one of the expandable electrodes contacts the target area to be ablated; and transmitting electrical energy to the contacted target area to ablate the target area by passing an electrical current between the expandable electrodes. 14. The method of claim 13, wherein transmitting the electrical energy comprises transmitting the electrical energy without causing permanent deformation to any of the expandable electrodes. (15) The method of claim 13, wherein expanding the expandable electrode distally relative to the distal end of the tube comprises expanding the expandable electrode by pushing the expandable electrode out of the distal end of the tube.

[0082] (16) The method of embodiment 13, wherein the expandable electrode is connected to a distal end of a shaft, and traversing the expandable electrode through the tube comprises traversing the expandable electrode through the tube using the shaft. (17) The method of embodiment 16, wherein the shaft includes at least one conductor configured to conduct the current to the electrode without permanently damaging the electrode. (18) The method of embodiment 13, wherein the tissue comprises a Marshall's ligament. (19) The method of embodiment 13, wherein transmitting the electrical energy comprises transmitting the electrical energy to irreversibly electroporate the target area. (20) The expandable electrode includes an inflatable balloon conductive proximal portion and an inflatable balloon conductive distal portion; 14. The method of claim 13, wherein expanding the expandable electrode comprises expanding the expandable electrode by inflating the balloon.

[0083] (21) The method of embodiment 20, wherein the length of the balloon is 2 to 20 times greater than the maximum cross-sectional diameter of the balloon. 22. The method of claim 20, wherein the balloon is shaped to define a plurality of openings through the wall of the balloon, and the method further comprises passing a fluid through the openings while transmitting the electrical energy.

Claims

1. 1. An apparatus comprising: A shaft and an inflatable balloon coupled to a distal end of the shaft, the balloon comprising: a proximal portion comprising a first tapered portion having a variable cross-sectional diameter that increases distally from a minimum cross-sectional diameter at a proximal end of the inflatable balloon to a maximum cross-sectional diameter, the first tapered portion being an ablation electrode that is electrically conductive along at least half of the circumference of the first tapered portion; a distal portion comprising a second tapered portion having a variable cross-sectional diameter that increases proximally from the minimum cross-sectional diameter at the distal end of the inflatable balloon to the maximum cross-sectional diameter, the second tapered portion being an ablation electrode that is electrically conductive around at least half of the circumference of the second tapered portion; an electrically insulating intermediate portion having the maximum cross-sectional diameter, the electrically insulating intermediate portion being disposed between the first and second sloped portions, connected to a distal portion of the first sloped portion and a proximal portion of the second sloped portion, and configured to insulate the proximal portion from the distal portion; The device, wherein the minimum cross-sectional diameter and the maximum cross-sectional diameter are diameters of the inflatable balloon in an inflated state.

2. The device of claim 1 , wherein the balloon is shaped to define a plurality of openings through the wall of the balloon.

3. The device of claim 1 , wherein the balloon further comprises an atraumatic tip disposed distally relative to the distal portion.

4. The device of claim 1 , wherein the distal end of the shaft protrudes from the balloon.

5. The device of claim 1 , wherein no conductive element is disposed on the electrically insulating intermediate portion.

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