Electrode edge transition for improved current density

Abstract

A catheter for ablating tissue by irreversible electroporation is disclosed. The catheter includes an elongate body having a proximal end and a distal end. The catheter also includes a first electrode spaced proximally from a second electrode along the elongate body, the first electrode and the second electrode each having a transition region terminating at opposing edges. The catheter further includes an insulator disposed on the electrode and extending between the first and second electrodes at the transition region. In the transition region, the electrode thickness of each electrode decreases toward the opposing edges, and the insulator thickness correspondingly increases to maintain a substantially constant total thickness.

Description

[Technical Field]

[0001] The present disclosure relates to medical systems and methods for ablating tissue in a patient. More particularly, the present disclosure relates to medical systems and methods for ablation of tissue by electroporation. [Background technology]

[0002] Ablation procedures are used to treat many different conditions in patients. Ablation can be used to treat cardiac arrhythmias, benign tumors, cancerous tumors, and to control bleeding during surgery. Ablation is typically achieved through thermal ablation techniques, including radiofrequency (RF) ablation and cryoablation. In RF ablation, a probe is inserted into the patient, and radio waves are transmitted through the probe to the surrounding tissue. The radio waves generate heat, which destroys the surrounding tissue and cauterizes blood vessels. In cryoablation, a hollow needle or cryoprobe is inserted into the patient, and a low-temperature, heat-conducting fluid is circulated through the probe, freezing and killing the surrounding tissue. RF ablation and cryoablation techniques indiscriminately kill tissue through cellular necrosis, which may damage or kill otherwise healthy tissue, such as tissue in the esophagus, phrenic nerve cells, and tissue in the coronary arteries.

[0003] Another cauterization technique uses electroporation. In electroporation, or electropermeabilization, an electric field is applied to cells to increase the permeability of the cell membrane. Electroporation may be reversible or irreversible, depending on the strength of the electric field. If electroporation is reversible, the increased permeability of the cell membrane may be utilized to introduce chemicals, drugs, and / or deoxyribonucleic acid (DNA) into the cells prior to cellular healing and recovery. If electroporation is irreversible, the affected cells die by apoptosis.

[0004] Irreversible electroporation can be used as a non-thermal ablation technique. Irreversible electroporation uses a train of short, high-voltage pulses to generate an electric field strong enough to kill cells by apoptosis. For cardiac tissue ablation, irreversible electroporation may be a safe and effective alternative to the indiscriminate killing of thermal ablation techniques such as RF ablation and cryoablation. Irreversible electroporation is used to kill target tissue, such as myocardial tissue, by using an electric field strength and duration that kills the target tissue while not permanently damaging other cells or tissues, such as non-target myocardial tissue, red blood cells, vascular smooth muscle tissue, endothelial tissue, and nerve cells. There is a continuing need for improved devices and methods for performing cardiac tissue ablation via irreversible electroporation. Summary of the Invention

[0005] In Example 1, a catheter for ablating tissue by irreversible electroporation comprises an elongate body having a proximal end and a distal end. The catheter also comprises a first electrode spaced proximally from a second electrode along the elongate body, the first electrode and the second electrode each having a transition region terminating at opposing edges. The catheter further comprises an insulator disposed over the electrode and extending between the first electrode and the second electrode at the transition region, wherein an electrode thickness of each electrode decreases toward the opposing edges and an insulation thickness of the insulator correspondingly increases in the transition region to maintain a substantially constant total thickness.

[0006] Example 2 is the catheter of Example 1, wherein each transition region has a substantially similar shape. Example 3 is the catheter of Example 1, wherein each transition region is configured such that when a voltage is applied to each of the plurality of electrodes, the current density within the transition region is approximately constant.

[0007] Example 4 is the catheter of Example 1, wherein each electrode has a constant taper angle in the transition region. Example 5 is the catheter of Example 1, wherein the insulator portion has a dielectric strength of approximately 15 kV / mm to 60 kV / mm.

[0008] Example 6 is the catheter of Example 5, wherein the dielectric strength of the insulator determines the gradient of the current density. Example 7 is the catheter of Example 1, wherein the transition region is formed by a tapered insulator on the electrode, thereby creating a gradual transition current density from the insulation perform to the electrode, thereby reducing the transition current density.

[0009] Example 8 is the catheter of example 1, wherein the transition region comprises one or more steps, ramps, or combinations of transitions of various geometries. Example 9 is the catheter of Example 1, further comprising a third electrode, a fourth electrode, and an insulator, wherein the diameter of each of the third electrode and the fourth electrode decreases toward the opposing edges in the transition region, and the insulator has a corresponding increase in diameter, such that the catheter shaft is substantially uniform in diameter.

[0010] Example 10 is the catheter of example 1, wherein the elongate body includes a tubular shaft having a proximal end and an opposite distal end. Example 11 is the catheter of Example 10, wherein the elongate body further comprises a plurality of splines, each spline comprising a distal end portion coupled to the central hub and a proximal end portion coupled to the tubular shaft.

[0011] Example 12 is the catheter of Example 11, wherein the first electrode and the second electrode are disposed on one of the plurality of splines. Example 13 is the catheter of Example 11, wherein the electrode assembly further comprises a plurality of proximal ablation electrodes positioned on each spline.

[0012] Example 14 is the catheter of example 10, wherein the first electrode and the second electrode are disposed on the tubular shaft. Example 15 is the catheter of Example 10, wherein each of the plurality of electrodes has a taper angle of about 20 to about 60 degrees in the transition region.

[0013] In Example 16, a catheter for ablating tissue by irreversible electroporation includes an elongate body extending along a longitudinal axis and having a proximal end and a distal end. The catheter also includes a first electrode spaced proximally from a second electrode along the elongate body, the first electrode and the second electrode each having a transition region terminating at opposing edges. The catheter further includes an insulator disposed over the electrode and extending between the first electrode and the second electrode at the transition region, wherein an electrode thickness of each electrode decreases toward the opposing edges and an insulation thickness of the insulator correspondingly increases to maintain a substantially constant total thickness.

[0014] Example 17 is the catheter of Example 16, wherein each transition region has a substantially similar shape. Example 18 is the catheter of example 16, wherein the transition region is configured such that when a voltage is applied to each of the plurality of electrodes, the current density within the transition region is approximately constant.

[0015] Example 19 is the catheter of Example 18, wherein each electrode has a constant taper angle in the transition region. Example 20 is the catheter of Example 16, wherein the insulator portion has a dielectric strength of about 15 kV / mm to 60 kV / mm.

[0016] Example 21 is the catheter of example 20, wherein the dielectric strength of the insulator determines the gradient of the current density. Example 22 is the catheter of Example 16, wherein the transition region is formed by a tapered insulator on the electrode, creating a gradual transition current density from the insulator to the electrode, thereby reducing the transition current density.

[0017] Example 23 is the catheter of example 16, wherein the transition region comprises one or more steps, ramps, or combinations of transitions of various geometries. Example 24 is the catheter of Example 16, further comprising a third electrode, a fourth electrode, and an insulator, wherein the diameter of each of the third electrode and the fourth electrode decreases toward the opposing edges in the transition region, and the insulator correspondingly increases in diameter, such that the catheter shaft is substantially uniform in diameter.

[0018] In Example 25, a catheter for ablating cardiac tissue by irreversible electroporation comprises an elongate shaft extending along a longitudinal axis and having a proximal end and a distal end. The catheter also comprises a tip electrode at the distal end of the elongate shaft and configured to provide a pulsed electric field ablation signal. The catheter comprises a ring electrode spaced proximally from the tip electrode and having a distal portion. The catheter further comprises an insulator disposed between the tip electrode and the first ring electrode, the distal portion of the ring electrode tapering distally along the longitudinal axis at the transition region, whereby an electrode thickness of the electrode decreases and an insulation thickness of the insulator increases to maintain a substantially uniform catheter diameter.

[0019] Example 26 is the catheter of Example 25, wherein the tip electrode tapers distally along the longitudinal axis in the transition region, thereby reducing the electrode thickness and increasing the insulator thickness to maintain a substantially uniform catheter diameter.

[0020] Example 27 is the catheter of Example 25, wherein each transition region has a substantially similar shape. Example 28 is the catheter of example 25, wherein the transition region is configured such that when a voltage is applied to each of the plurality of electrodes, the current density within the transition region is approximately constant.

[0021] Example 29 is the catheter of Example 28, wherein each electrode has a constant taper angle in the transition region. Example 30 is the catheter of Example 25, wherein the insulator portion has a dielectric strength of about 15 kV / mm to 60 kV / mm.

[0022] Example 31 is the catheter of example 30, wherein the dielectric strength of the insulator determines the gradient of the current density. Example 32 is the catheter of Example 25, wherein the transition region is formed by a tapered insulator on the electrode, thereby creating a gradual transition current density from the insulation perform to the electrode, thereby reducing the transition current density.

[0023] Example 33 is the catheter of example 25, wherein the transition region comprises one or more steps, ramps, or combinations of transitions of various geometries. Example 34 is the catheter of Example 25, wherein the elongate shaft further comprises a third electrode, a fourth electrode and an insulator, and the third electrode tapers distally along the longitudinal axis in the transition region, whereby the electrode thickness decreases and the insulator thickness increases to maintain a substantially uniform catheter diameter.

[0024] Example 35 is a method of making a catheter for ablating cardiac tissue by irreversible electroporation, the method including providing an elongate shaft extending along a longitudinal axis and having a proximal end and a distal end. The method also includes securing a first electrode spaced apart from a second electrode along the elongate shaft, each of the plurality of electrodes having a transition region terminating at opposing edges. The method further includes securing an insulator disposed on the electrode at the transition region and extending between the first electrode and the second electrode, wherein a diameter of each of the first electrode and the second electrode decreases toward the opposing edges at the transition region, and the insulator correspondingly increases in diameter, such that the catheter shaft is substantially equal in diameter.

[0025] While multiple embodiments are disclosed, still other embodiments of the present disclosure will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the present disclosure. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 illustrates an exemplary clinical setting for treating a patient and for treating the patient's heart using an electrophysiology system according to embodiments of the presently disclosed subject matter. [Figure 2] 2 is an isometric view of a distal portion of a cardiac ablation catheter for use in the electrophysiology system of FIG. 1 in accordance with an embodiment of the presently disclosed subject matter. [Figure 3] 2 is an isometric view of a distal portion of a splined catheter for use in the electrophysiology system of FIG. 1 in accordance with an embodiment of the presently disclosed subject matter. [Figure 4A] 1 shows the current density generated near the edge of the ablation electrode of a conventional pulsed electric field ablation catheter compared to an improved edge-graded pulsed electric field ablation catheter during operation. [Figure 4B]1 shows the current density generated near the edge of the ablation electrode of a conventional pulsed electric field ablation catheter compared to an improved edge-graded pulsed electric field ablation catheter during operation. [Figure 5A] 10 illustrates exemplary electrode edge transition phases according to embodiments of the presently disclosed subject matter. [Figure 5B] 10 illustrates exemplary electrode edge transition phases according to embodiments of the presently disclosed subject matter. [Figure 5C] 10 illustrates exemplary electrode edge transition phases according to embodiments of the presently disclosed subject matter. [Figure 5D] 10 illustrates exemplary electrode edge transition phases according to embodiments of the presently disclosed subject matter.

[0027] While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and described in detail below. The intention, however, is not to limit the disclosure to the specific embodiments described. On the contrary, the disclosure is intended to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure as defined by the appended claims. DETAILED DESCRIPTION OF THE INVENTION

[0028] To promote an understanding of the principles of the present disclosure, reference is made to examples illustrated in the drawings described below. The illustrated examples disclosed herein are not intended to be exhaustive or to limit the disclosure to the precise form disclosed in the following detailed description. Rather, these exemplary embodiments were chosen and described to enable those skilled in the art to utilize its teachings. Applying some (e.g., all) features of an example embodiment to all examples does not depart from the scope of the present disclosure. Thus, no figure should be interpreted as having any dependency or requirement relating to any single component or combination of components illustrated therein. Furthermore, various components illustrated in a figure may, by way of example, be combined with various other components illustrated in that figure (and / or components not illustrated), all of which are considered to be within the scope of the present disclosure.

[0029] The terms "couples," "coupled," "connected," "attached," and the like, along with variations thereof, are used to include both arrangements in which two or more components are in direct physical contact, and arrangements in which two or more components are not in direct contact with each other (e.g., the components are "coupled" through at least a third component), but still cooperate or interact with each other.

[0030] Throughout this disclosure and in the claims, numerical terms such as first and second are used in reference to various components or features. Such use is not intended to indicate an ordering of the components or features. Rather, the numerical terms are used to aid the reader in identifying the referenced component or feature and should not be narrowly construed as providing a particular ordering of the components or features.

[0031] 1 illustrates an exemplary clinical setting 10 for treating a patient 20 and for treating a heart 30 of the patient 20 using an electrophysiology system 50 according to an embodiment of the presently disclosed subject matter. The electrophysiology system 50 includes an electroporation device 60 and an optional localization field generator 80. The clinical setting 10 also includes additional equipment, such as an imaging device 94 (represented by a C-arm), and various control elements configured to allow a practitioner to control various aspects of the electrophysiology system 50. As will be appreciated by those skilled in the art, the clinical setting 10 may have other components and arrangements of components not shown in FIG. 1 .

[0032] Electroporation device 60 includes a cardiac ablation catheter 105, an introducer sheath 110, a controller 90, and an electroporation generator 130. In an embodiment, electroporation device 60 is configured to deliver electric field energy to target tissue within a patient's heart 30 to produce tissue apoptosis and render the tissue unable to conduct electrical signals. Controller 90 is configured to control functional aspects of electroporation device 60. In an embodiment, controller 90 is configured to control electroporation generator 130 to generate electrical pulses, e.g., electrical pulse magnitude, electrical pulse timing, and duration. In an embodiment, electroporation generator 130 is operable as a pulse generator to generate and deliver pulse sequences to cardiac ablation catheter 105.

[0033] In an embodiment, the introducer sheath 110 is operable to provide a delivery conduit through which the cardiac ablation catheter 105 may be deployed to a particular target site within the patient's heart 30. However, it will be understood that the introducer sheath 110 is merely shown and described herein to provide context for the overall electrophysiology system 50.

[0034] In the illustrated embodiment, the cardiac ablation catheter 105 includes a handle 105a, an elongate shaft 105b, and a distal portion 150. As shown, the shaft has a distal end 105c and a proximal end 105d, with the proximal end 105d of the shaft 105b extending distally from the handle 105a. The handle 105a is configured to be manipulated by a user to position the distal portion 150 at a desired anatomical location. The shaft 105b generally defines a longitudinal axis of the cardiac ablation catheter 105. The shaft 105b may include a molded articulation joint for spine reinforcement and maneuverability. Further details can be found in U.S. Patent Application No. 63 / 129,960, which is incorporated herein by reference in its entirety.

[0035] As shown, distal portion 150 is located at or adjacent to distal end 105c of shaft 105b. In an embodiment, distal portion 150 is electrically coupled to electroporation generator 130 to receive an electrical pulse sequence or train, thereby selectively generating an electric field for ablation of target tissue by irreversible electroporation.

[0036] In some embodiments, the cardiac ablation catheter 105 is a point catheter that includes a linear body toward its distal end. In some embodiments, the distal portion 150 includes one or more electrodes disposed on the shaft 105b. In some implementations, the distal portion 150 includes one or more electrode pairs. In some embodiments, the distal portion 150 includes one or more ablation electrodes and one or more detection electrodes. In some implementations, the distal portion 150 includes an ablation electrode pair configured to generate an electric field sufficient for irreversible electroporation ablation. In some examples, the ablation electrode pair includes a tip electrode covering the distal end of the catheter 105 and a ring electrode disposed proximate the tip electrode. As used herein, a ring electrode refers to an electrode having a ring shape. In some designs, the ablation electrode pair includes two ring electrodes disposed proximate the distal end of the catheter 105.

[0037] In embodiments, the location and size of the electrodes are specifically designed to allow for flexibility. For example, the electrodes are designed to be relatively short in length. As another example, two electrodes have a relatively large spacing to allow for flexibility and / or deflection. In some embodiments, the one or more electrodes include one or more pairs of ablation electrodes and one or more pairs of detection electrodes. The detection electrodes may be used to detect electrical signals related to the patient's heart, allowing the operator or the system to determine whether ablation has occurred. In some designs, the electrical signals can be used to determine the position or proximity of the cardiac ablation catheter 105. In some embodiments, other sensors, such as force sensors, navigation sensors (e.g., five- or six-degree-of-freedom (“DoF”) sensors), etc., may be incorporated into the distal portion 150.

[0038] In some embodiments, one or more sensing electrodes on the cardiac ablation catheter 105 can measure electrical signals and generate output signals that may be processed by a controller (e.g., controller 90) to generate an electroanatomical map. In some examples, the electroanatomical map is generated before ablation to determine the electrical activity of cardiac tissue within the target heart chamber. In some examples, the electroanatomical map is generated after ablation to verify desired changes in the electrical activity of the ablated tissue and the heart chamber as a whole. The sensing electrodes may be used to determine the position of the catheter 105 in three-dimensional space within the body. For example, as the operator moves the catheter 105 within the patient's heart chamber, the boundaries of catheter movement can be determined by controller 90, which may include or be coupled to a mapping and navigation system, thereby mapping the anatomical structure of the heart chamber. The anatomical structures of the heart chambers may be used to facilitate navigation of the catheter 105 without the use of ionizing radiation such as fluoroscopy, and the anatomical structures of the heart chambers may be used to guide the ablation interval and to tag the location of the ablation when it is completed to assist the surgeon in completely ablating the target anatomy.

[0039] According to embodiments, various components of electrophysiology system 50 (e.g., controller 90) may be implemented on one or more computing devices. The computing devices may include any type of computing device suitable for implementing embodiments of the present disclosure. Examples of computing devices include general-purpose or special-purpose computing devices such as workstations, servers, laptops, portable devices, desktops, tablet computers, handheld devices, general-purpose graphics processing units (GPGPUs), and the like, all of which are discussed with reference to various components of system 50 within FIG. 1 .

[0040] In some embodiments, a computing device includes a bus that directly and / or indirectly couples the following devices: a processor, memory, input / output (I / O) ports, I / O components, and a power supply. Any number of additional components, different components, and / or combinations of components may also be included in a computing device. Bus refers to what may be one or more buses (e.g., an address bus, a data bus, or a combination thereof). Similarly, in some embodiments, a computing device may include several processors, several memory components, several I / O ports, several I / O components, and / or several power supplies. Additionally, any number of these components or combinations thereof may be distributed and / or replicated across several computing devices.

[0041] In some embodiments, system 50 includes one or more memories (not shown). The one or more memories may include computer-readable media in the form of volatile and / or non-volatile memory, transient and / or non-transitory storage media, and may be removable, non-removable, or a combination thereof. Examples of media include random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory, optical or holographic media, magnetic storage devices such as magnetic cassettes, magnetic tape, magnetic disk storage devices, data transmission, and / or any other medium that can be used to store information and that can be accessed by a computing device, such as, for example, quantum state memory. In some embodiments, the one or more memories store computer-executable instructions for causing a processor (e.g., controller 90) to implement aspects of embodiments of the system components discussed herein and / or to perform aspects of embodiments of the methods and procedures discussed herein.

[0042] Computer-executable instructions may include, for example, computer code, machine-usable instructions, etc., such as, for example, program components that are executable by one or more processors associated with a computing device. The program components may be programmed using any number of different programming environments, including various languages, development kits, frameworks, etc. Some or all of the functionality contemplated herein may also or alternatively be implemented in hardware and / or firmware.

[0043] In some embodiments, the memory may include a data repository implemented using any one of the configurations described below. The data repository may include random access memory, flat files, XML files, and / or one or more database management systems (DBMS) running on one or more database servers or data centers. The database management system may be a relational (RDBMS), hierarchical (HDBMS), multidimensional (MDBMS), object-oriented (ODBMS or OODBMS), or object-relational (ORDBMS) database management system, etc. The data repository may be, for example, a single relational database. In some cases, the data repository may include multiple databases whose data can be exchanged and aggregated by a data integration process or software application. In exemplary embodiments, at least a portion of the data repository may be hosted in a cloud data center. In some cases, the data repository may be hosted on a single computer, server, storage device, cloud server, etc. In some other cases, the data repository may be hosted on a series of networked computers, servers, or devices. In some cases, the data repository may be hosted on multiple tiers of data storage devices, including local, regional, and central.

[0044] The various components of the system 50 may communicate or be coupled via a communication interface, e.g., a wired or wireless interface. The communication interface includes, but is not limited to, any wired or wireless short-range and long-range communication interface. The wired interface may use a cable, umbilical, or the like. The short-range communication interface may be, for example, a local area network (LAN), an interface conforming to a known communication standard, i.e., the Bluetooth® standard, an IEEE 702 standard (e.g., IEEE 702.11), ZigBee® or similar specifications, such as those based on the IEEE 702.15.4 standard, or other known or proprietary wireless protocols. The long-range communication interface may be, for example, a wide area network (WAN), a cellular network interface, a satellite communication interface, or the like. The communication interface may be within a private computer network, such as an intranet, or over a public computer network, such as the Internet.

[0045] As described in more detail elsewhere herein, various embodiments of the present disclosure, particularly the distal portion 150, employ novel structural features that improve clinical performance and enhance manufacturability of the ablation catheter 105. Specifically, the distal portion 150 includes, among other things, portions of insulation that operate to support and position the tip electrode and adjacent ring electrode, as well as to electrically isolate the various electrical components of the distal portion 150.

[0046] 2 is an isometric view of a distal portion of a cardiac ablation catheter 200. In an embodiment, cardiac ablation catheter 200 corresponds to ablation catheter 105 shown in FIG.

[0047] As shown, the distal portion 202 is disposed axially along a longitudinal axis 204 defined by the shaft (not shown in FIG. 2 ) of the ablation catheter 200. The distal portion 202 includes an electrode pair 208 including a tip electrode 212 and a ring electrode 214, where the tip electrode 212 is located at the distal end of the distal portion 202 and the ring electrode 214 is located proximal to and spaced apart from the tip electrode 212. As shown, the ring electrode has a distal leading end 214a and a proximal trailing end 214b. In embodiments, the distal portion 202 may include additional electrodes, such as an additional electrode pair 210, where the additional electrode pair 210 includes electrodes 216, 218 disposed proximally to and spaced apart longitudinally from the electrodes 212, 214. More or fewer electrodes may be employed in other embodiments within the scope of the present disclosure.

[0048] The operation of the various electrodes (or electrode pairs) may vary depending on the clinical application of the ablation catheter 200. In various embodiments, electrodes 212, 214, 216, and 218 are configured to operate as ablation electrodes, detection electrodes, or both. For example, any or all of electrodes 212, 214, 216, and 218 can be configured to be operable for delivery of ablation energy to target tissue. Additionally or alternatively, any or all of electrodes 212, 214, 216, and 218 may be operable as detection electrodes configured to detect electrical signals (e.g., intrinsic cardiac activation signals and / or electric fields generated by injected currents for use in impedance-based position tracking, tissue proximity detection, or contact detection, etc.). In some embodiments, electrode pair 208 may be configured to operate as ablation electrodes for bipolar delivery of ablation energy, particularly pulsed electric field ablation energy for localized ablation of cardiac tissue. In embodiments, electrodes 216, 218 may be operable as detection electrodes or alternatively as ablation electrodes. In some examples, the second electrode pair 210 may be configured to measure local impedance and also function as a position sensor to detect local electric fields in five degrees of freedom (e.g., five different motions (x, y, z, acceleration, and rotation)). Except as specifically described herein in an embodiment, the electrodes 212, 214, 216, and 218 may be configured according to that described in co-pending and commonly assigned U.S. patent application Ser. No. 63 / 194,716, which is incorporated herein by reference in its entirety.

[0049] In one exemplary embodiment, electrode pair 208 may be activated with a first polarity, and electrode pair 210 may be activated with a second polarity opposite the first polarity, thereby defining an ablation vector and corresponding electric field therebetween. However, it is emphasized that the present disclosure is not limited to the particular electrode configuration and number of electrodes shown in FIG. 2. Rather, one skilled in the art will understand that further variations in electrode configuration, number of electrodes, etc. may be employed within the scope of the present disclosure.

[0050] In the illustrated embodiment, the distal portion 202 includes a section of insulator 220 located between the tip electrode 212 and the ring electrode 214. In the illustrated embodiment, the insulator section 220 includes a distal section 220a and a proximal section 220b (partially illustrated in FIG. 2). As further shown, the distal section 220a of the insulator section 220 is disposed between the tip electrode 212 and the ring electrode 214 and over a portion of the proximal section 220b, such that the distal leading end 214a of the ring electrode 214 abuts a radial shoulder of the insulator section 220. The insulator section 220 includes a longitudinal spacing along the longitudinal axis 204 between the tip electrode 212 and the distal leading end 214a of the ring electrode 214. In the illustrated embodiment, the insulator section 220 provides an insulating layer between conductive surfaces and wires that are at high potential relative to one another within the distal region of the catheter.

[0051] In some instances, the insulator section provides a means for routing the conductive wires 226 through the distal portion 202. In some instances, the insulator section provides a positive placement feature for tip components, allowing for better component spacing and fit (i.e., mold-fit) in subsequent processing steps. In some instances, the insulator section provides protection for components of the cardiac ablation catheter 200, such as navigation sensors or thermocouples, during various use conditions.

[0052] In various embodiments, the distal portion 202 further includes an insulating material 230 disposed at least proximal to the ring electrode 214, encapsulating and forming an outer insulating surface of the distal portion 202. In embodiments, the insulating material 230 is disposed between the ring electrodes 214 and 216. In some embodiments, the insulating material 230 is formed by an overmolding process. Alternatively, the insulating material 230 may be formed using a reflow process, as known in the art, in which one or more tubular segments of insulating material are disposed around the partially assembled distal portion 202 and then heated. In other embodiments, the insulating material 230 is pre-molded and pre-formed. Embodiments employing an overmolding process to provide the insulating material 230 may have certain advantages, such as reducing or even eliminating the need for subsequent processing (such as injecting medical adhesives to complete the assembly process and provide fluid-tight connections between various components). The insulating material may be commercially available Pebax® 55D and Pelathane® 55D. Both materials may be used in a post-molding process and bonded to "epoxy bondable" wire insulation. Pellethane® can be bonded to the tip insulation using a primer (e.g., Sivate® E610) and plasma. Pebax® can be bonded to the tip insulation using an adhesive (e.g., Thermedics 1-MP) without plasma.

[0053] 3 is a partial perspective view of a cardiac ablation catheter 300 having a catheter distal section 302 according to an embodiment of the present disclosure. In this embodiment, cardiac ablation catheter 300 corresponds to ablation catheter 105 shown in FIG.

[0054] As shown, the ablation catheter 300 includes a tubular outer shaft 308 having a shaft distal end 309 and an electrode assembly 310 extending distally from the distal end 309 of the outer shaft 308. In an embodiment, the electrode assembly 310 is configured to self-expand from a contracted configuration when constrained within a delivery sheath to a predefined expanded configuration defining an interior space 312. As described in more detail herein, the electrode assembly 310 includes a plurality of ablation electrodes configured to receive pulsed electrical signals from the electroporation console 130 of FIG. 1 to generate a pulsed electric field sufficient to ablate target tissue via irreversible electroporation. Additionally, the electrode assembly 310 further includes a plurality of mapping and detection electrodes configured to, among other things, detect cardiac electrical signals to detect the location of the electrode assembly 310 within the patient's anatomy and determine proximity to target tissue within the anatomy.

[0055] In the illustrated embodiment, the electrode assembly 310 includes a distally located central hub portion 314 and a plurality of splines 316A-316F extending proximally from the central hub portion 314. As further shown, each spline 316A-316F has a distal end portion 317 and a proximal end portion 318. While the distal end portion 317 and the proximal end portion 318 are only shown on spline 316C in FIG. 3 , each of the plurality of splines 316A-316F also has a distal end portion 317 and a proximal end portion 318. As shown, the proximal end portion 318 is attached to and constrained to the distal end 309 of the outer shaft 302. In embodiments, the specific geometries of the splines 316A-316F and associated components (e.g., ablation electrodes and mapping electrodes) are optimized to provide desired mechanical and therapeutic / diagnostic performance.

[0056] In the illustrated embodiment, the splines 316A-316F are comprised of a support member 320 and a flexible circuit 322 secured to and disposed on the outer surface of the support member 320. The support member 320 functions, among other things, as the primary structural support for the electrode assembly 310 and therefore primarily determines the mechanical properties of the electrode assembly 310. In an embodiment, the support member 320 is formed from a superelastic material (metal or polymer) that provides the electrode assembly 310 with the desired mechanical / structural properties. In an embodiment, the support member 320 is formed from a superelastic metal alloy, such as a nickel-titanium alloy.

[0057] Support member 320 includes a support member hub 324 and multiple support member branches. In embodiments, the support member branches can be selectively configured along their lengths to adjust the mechanical properties of electrode assembly 310. As shown, flexible circuit 322 includes a distal ablation electrode 338. Flexible circuit 322 further includes multiple proximal ablation electrodes 344 and multiple spline detection electrodes 350. While proximal ablation electrode 344 and spline detection electrode 350 are only shown on spline 316C, each of multiple splines 316A-316F includes a proximal ablation electrode 344 and multiple spline detection electrodes 350. In some embodiments, insulators are used to create a surface flush with the electrode spline surface. In other embodiments, only a portion of the transition region is covered. In such embodiments, one or more electrodes protrude from the electrode spline surface.

[0058] In the illustrated embodiment, each of the plurality of spline detection electrodes 350 is disposed within the periphery of one of the plurality of proximal ablation electrodes 244 or within the periphery of one of the radial segments of the plurality of distal ablation electrodes 338. For example, as shown, each of the distal-most spline detection electrodes 350 is disposed within the periphery of a respective one of the plurality of radial segments of the distal ablation electrode 338 and is electrically insulated from the distal ablation electrode 338. In addition, the more proximal spline detection electrodes 350 are disposed along and within the periphery of and electrically insulated from a respective one of the plurality of proximal ablation electrodes 344.

[0059] 4A and 4B show the current densities generated near the edge of the ablation electrode of a conventional pulsed electric field ablation catheter compared to an improved edge-graded pulsed electric field ablation catheter during operation. The current densities described and generated in FIGS. 4A and 4B are in the outer portions of the electrodes and show only half of the cross section of cardiac ablation catheter 200 of FIG. 2. As shown, according to an embodiment of the present disclosure, first electrode 414, section of insulator 420, and second electrode 412 correspond to ring electrode 214, section of insulator 220, and tip electrode 212 of FIG. 2.

[0060] As shown in FIG. 4A , a conventional pulsed electric field ablation design produces an ablation current density 401 when a voltage is applied to a first electrode 414. At the intersection of the electrode and a portion of insulator 420, the current density 401 increases significantly, for example, approximately doubling the current density in some cases. As shown, conventional pulsed electric field ablation electrodes produce high current density peaks at multiple electrode edges. “Edge” or “electrode edge” refers to the transition region between the metal electrode and the portion of insulator. These high current peaks can induce arcing, as illustrated by ablation current densities 401 and 402. Electrical arcing can cause a variety of problems, including thermal injury, gas embolization, and inefficient ablation energy delivery, among other issues.

[0061] As shown in FIG. 4B, the improved edge-graded pulsed electric field ablation design produces more consistent current densities 403 and 404. As shown, each facing electrode pair includes opposing edges. A first electrode 414 is spaced apart from a second electrode 412, and each of the electrodes has a transition region that terminates at the opposing edge. A portion of insulator 420 is disposed on the electrode within the transition region and extends between the first electrode 414 and the second electrode 412. As shown, unlike the conventional transition from electrode to insulator in FIG. 4A, the improved edge-graded design includes gradual transition zones 405 and 406. In the transition zones 405 and 406, the diameter (or thickness) of the electrode gradually decreases in a direction toward the opposing edge, while the thickness of the insulator increases in a complementary manner, resulting in a substantially isodiametric structure of the electrode and insulator combination. In embodiments, transition zones 405 and 406 may be made from a different insulating material than the remainder of insulator portion 420. For example, transition zones 405 and 406 may be made from a semi-conductive material, while the remainder of insulator portion 420 may be completely insulating.

[0062] As shown in FIG. 4B, the transition zones 405 and 406 are defined by a spacing length L1. The spacing length L1 defines the longitudinal region between the first electrode 414 and the second electrode 412. As the length L1 decreases, the current density generated on the ablation electrodes within the transition zones 405 and 406 increases. As shown, the zones 405 and 406 create a transition region where the electrode thickness (or diameter) decreases and the insulating layer thickness increases. This transition region mitigates the current density peaks seen in conventional designs. In various embodiments, the current density generated within the electrodes and the transition region remains approximately constant. The optimal angle for the tapered transition zones 405 and 406 is one that avoids the current density spikes seen in FIG. 4A. In some embodiments, the taper angle in the transition zones 405 and 406 is between 20 and 60 degrees, while in other embodiments, the taper angle in the transition zones is between 30 and 45 degrees.

[0063] As shown in transition zone 406, the current density 404 gradually increases from the mostly insulated electrode edge to the fully uninsulated electrode. In addition, the thickness of the insulation portion 420 gradually decreases from 100% to 0%. The improved gradual edge transition design therefore reduces the current density generated on the ablation electrode in the transition zone. This improved design eliminates the large current density peaks generated in conventional pulsed electric field ablation designs, thus eliminating the risk of electric arcing, sparks, localized heating, and electrolytic gas production, among many other problems.

[0064] In embodiments, electrode wall thickness may range from 0.0001 inches (0.00254 mm), such as the cardiac ablation catheter 300 of FIG. 3, to 0.010 inches (0.254 mm) for larger electrodes. In a further embodiment, assuming an electrode wall thickness of 0.006 inches (0.15 mm), full-thickness insulation at the electrode edge can withstand 3 kV, exceeding the maximum voltage of most pulsed electric field ablation energy applications for cardiac ablation. The dielectric strength of the insulator determines the current density gradient. The dielectric strength may range from approximately 15 kV / mm to 60 kV / mm. In embodiments, insulating materials may include polyurethane, PEBAX®, polyetheretherketone (PEEK), polycarbonate, Isoplast®, among others.

[0065] 5A-5D show four other exemplary electrode edge transition phases according to embodiments of the presently disclosed subject matter. FIGS. 5A-5D show half of an electrode edge transition section. As shown, the ideal transition need not be perfectly linear. FIG. 5A shows a stepped, trapezoidal current density electrode edge transition section 501. FIG. 5B shows an outwardly curved current density electrode edge transition section 502. FIG. 5C shows an inwardly curved current density electrode edge transition section 503. FIG. 5D shows a multi-step current density electrode edge transition section 504. Therefore, a combination of one or more steps, ramps, or transitions of various geometries may be desirable to achieve maximum functionality.

[0066] In the various embodiments described above, insulation can be added to the transition region using several techniques, including, for example, forming, reflow, lamination overlay, fluoromasking, or lamination of layers with adhesives. Additionally, the electrode surface may be textured in the transition region to increase surface area and improve the insulating bond. In some cases, the electrode surface may be treated with a primer or other bonding agent to improve the insulating bond. In embodiments, electrode edges are rounded or radiused. Inner edges may be broken or radiused to prevent mechanical damage from bending during device fabrication and function.

[0067] In embodiments, conductive polymers may be used in the insulating transition region to gradually change resistivity. This may be done in addition to or instead of the tapered wall thickness of the electrode or insulating material described above. These polymers include, but are not limited to, polyacetylene, polypyrrole, polyindole, polyaniline and their copolymers, and poly(p-phenylene vinylene) (PPV) and its soluble derivatives. These polymers allow for tunable resistivity and may perform better than typical insulating polymers. Additionally, in some cases, conductive polymers may be applied to the transition region to counteract the high current densities that may occur in thinner insulating regions.

[0068] It should be noted that although the above embodiments are described with respect to a bipolar ablation configuration, the concepts described may also be applied to a monopolar ablation configuration, in which, for example, a monopolar ablation electrode may extend from an electrode on the catheter to a return electrode positioned outside the heart, e.g., an external electrode placed on the patient's skin.

[0069] Embodiments of the present disclosure provide systems, devices, and methods for the selective and rapid application of pulsed electric fields to ablate tissue via irreversible electroporation. In general, the systems, devices, and methods described herein may be used to generate high electric field intensities in desired target regions while reducing peak electric field values ​​elsewhere to reduce unwanted tissue damage and electrical arcing. The irreversible electroporation systems described herein may include a signal generator and processor configured to apply one or more voltage pulse waveforms to a selected set of electrodes of an ablation device to deliver energy to a target region (e.g., ablation energy for a set of tissue within a pulmonary vein orifice or sinus). The pulse waveforms disclosed herein may aid in the therapeutic treatment of various cardiac arrhythmias (e.g., atrial fibrillation). To deliver the pulse waveforms generated by the signal generator, one or more electrodes of the ablation device may have insulated electrical leads configured to maintain a voltage potential of hundreds to thousands of volts. The multiple electrodes may be independently addressable, such that each electrode can be controlled (e.g., deliver energy) independently of any other electrode of the device. In this way, multiple electrodes can synergistically deliver different energy waveforms at different times for electroporation of tissue.

[0070] It is fully understood that methods including one or more steps, in the order listed, are not limitations on the scope of the claims unless expressly or implicitly stated to the contrary in the specification or in the claims themselves. It is also fully recognized that the methods shown are only a few examples of many disclosed, and that some steps may be added or omitted without departing from the scope of the present disclosure. Such steps may include incorporating devices, systems, or methods, or components thereof, as well as matters that are well understood, routine, and conventional in the art.

[0071] The connecting lines shown in the various figures contained herein are intended to represent example functional relationships and / or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may exist in a practical system. However, benefits, advantages, solutions to problems, and any elements that may cause or make more noticeable any benefit, advantage, or solution should not be construed as critical, necessary, or essential features or elements. Accordingly, the scope should not be limited except by the appended claims, and references to elements in the singular are not intended to mean "one and only one," unless expressly so stated, but rather "one or more." Furthermore, when phrases similar to "at least one of A, B, or C" are used in the claims, this phrase is intended to be interpreted to mean that only A may be present in an embodiment, that only B may be present in an embodiment, that only C may be present in an embodiment, or that any combination of elements A, B, or C may be present in a single embodiment, e.g., A and B, A and C, B and C, or A and B and C.

[0072] References in the Detailed Description herein to "one embodiment," "an embodiment," "an exemplary embodiment," etc., indicate that the described embodiment may include a particular feature, structure, or characteristic, but not all embodiments necessarily include that particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in the context of one embodiment, it is believed to be within the knowledge of one of ordinary skill in the art having the benefit of this disclosure to affect such feature, structure, or characteristic in the context of other embodiments, whether or not explicitly stated. After reading the specification, it will be apparent to one of ordinary skill in the art how to implement the present disclosure in alternative embodiments.

[0073] Furthermore, no element, component, or method step in this disclosure is intended to be made available to the public, regardless of whether that element, component, or method step is expressly recited in a claim. No claim element herein is to be construed under the provisions of 35 U.S.C. 112(f) unless the element is expressly recited using the phrase "means for." As used herein, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion; thus, a process, method, article, or device comprising a list of elements may include not only those elements, but also other elements not expressly listed or inherent to such process, method, article, or device.

[0074] Various modifications and additions may be made to the exemplary embodiments described without departing from the scope of the present disclosure. For example, while the above-described embodiments refer to particular features, the scope of the present disclosure also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present disclosure is intended to embrace all such alternatives, modifications, and variations that fall within the scope of the claims, including all equivalents thereof.

Claims

1. 1. A catheter for ablating tissue by irreversible electroporation, comprising: an elongate body having a proximal end and a distal end; a first electrode spaced proximally from a second electrode along the elongate body, the first electrode and the second electrode each having a transition region terminating at opposing edges; an insulator disposed over the electrodes in the transition region and extending between the first electrode and the second electrode; A catheter wherein in the transition region, the electrode thickness of each electrode decreases toward the opposing edge, and the insulation thickness of the insulator correspondingly increases, thereby maintaining a substantially constant total thickness.

2. The ablation catheter of claim 1 , wherein each transition region has a substantially similar shape.

3. The ablation catheter of claim 1 , wherein each transition region is configured such that when a voltage is applied to each of the plurality of electrodes, the current density within the transition region is approximately constant.

4. The ablation catheter of claim 1 , wherein each electrode has a constant taper angle in the transition region.

5. The ablation catheter of claim 1 , wherein the insulator portion comprises a dielectric strength of about 15 kV / mm to 60 kV / mm.

6. The ablation catheter of claim 5 , wherein the dielectric strength of the insulator determines a gradient of current density.

7. 10. The ablation catheter of claim 1, wherein the transition region is defined by tapered insulation on the electrode, thereby creating a gradual transition of current density from the insulation to the electrode, thereby reducing the transition of current density.

8. The ablation catheter of claim 1 , wherein the transition region comprises a combination of one or more steps, ramps, or transitions of various geometries.

9. 10. The ablation catheter of claim 1, further comprising third and fourth electrodes and insulators, wherein the diameters of the third and fourth electrodes each decrease toward the opposing edges in the transition region, and the insulators correspondingly increase in diameter, such that the catheter shaft is substantially uniform in diameter.

10. The ablation catheter of claim 1 , wherein the elongate body includes a tubular shaft having a proximal end and an opposite distal end.

11. The ablation catheter of claim 10 , wherein the elongate body further comprises a plurality of splines, each spline including a distal end portion coupled to a central hub and a proximal end portion coupled to the tubular shaft.

12. The ablation catheter of claim 11 , wherein the first electrode and the second electrode are disposed on one of the plurality of splines.

13. The ablation catheter of claim 11 , wherein the electrode assembly further comprises a plurality of proximal ablation electrodes located on each spline.

14. The ablation catheter of claim 10 , wherein the first electrode and the second electrode are disposed on the tubular shaft.

15. The ablation catheter of claim 10 , wherein each of the plurality of electrodes has a taper angle of about 20 to about 60 degrees in the transition region.

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