Tissue ablation electrodes and catheters

Abstract

An ablation catheter (20) is provided that includes a shaft (22) including a distal electrode-support portion (26, 126) that includes electrical insulation (30). An electrically- conductive electrode (24) includes an uninsulated electrode surface (40) disposed on an outer surface (42) of the distal electrode-support portion (26, 126), and an insulated electrode surface (44). The electrical insulation (30) insulates the insulated electrode surface (44) with respect to outside the distal electrode-support portion (26, 126), The insulated electrode surface (44) is shaped to define one or more curved surface portions (50) that face only partially radially outward, and do not face even partially radially inward, with respect to a central longitudinal axis (28) of the distal electrode- support portion (26, 126). For each of all points (60) on the one or more curved surface portions (50), a line (62), which is perpendicular to the central longitudinal axis (28) and intersects the central longitudinal axis (28) and the point (60), defines an oblique angle with the curved surface portion (50) at the point (60). Other embodiments are also described.

Description

[0001] TISSUE ABLATION ELECTRODES AND CATHETERS

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims priority from US Provisional Application 63 / 744,773, filed January 13, 2025, and US Provisional Application 63 / 762,948, filed February 25, 2025. All of the above-referenced applications are assigned to the assignee of the present application and incorporated herein by reference.

[0003] FIELD OF THE APPLICATION

[0004] The present invention relates generally to transcatheter surgical methods, and specifically to transcatheter surgical methods for treating cardiac arrhythmias.

[0005] BACKGROUND OF THE APPLICATION

[0006] Tissue ablation is a procedure that can create continuous or segmented lesions in tissue, such as cardiac tissue. Ablation methods can be thermal or non-thermal. Pulsed Field Ablation (PF A) is a type of non-thermal ablation method. Existing PFA electrodes have significant limitations, including (i) generation of field hotspots that can lead to uneven ablation, bubble formation, and increased collateral damage, (ii) hemolysis risk due to energy spillover into surrounding blood flow, which damage red blood cells and compromise safety when used in subjects, and (iii) creation of irregular lesion shapes from non-uniform fields.

[0007] PCT Publication WO 2023 / 018937 to Chambers provides systems and methods for treating atrial arrhythmia. A system can comprise an elongate proximal shaft and a distal ablation probe, which is: (a) supported at a distal end of the elongate proximal shaft, (b) shaped, when unconstrained, so as to define at least first and second elongate ablating surfaces running alongside each other, and (c) configured to make, in an atrial wall of a heart, one or more ablation lesions that include at least first and second elongate continuous ablation lesion segments that are spaced apart and run alongside each other. The method uses the system to make the lesions.

[0008] US Patent 11,051,878 to Helgeson et al. describes an elongate medical device shaft that may comprise an elongate body and an annular electrode disposed on the elongate body. The annular electrode may define a longitudinal axis and have an outer diameter. Theouter diameter may be greater at an axial center of the electrode than at an axial end of the electrode. Additionally or alternatively, the elongate body may comprise three longitudinal sections having three wall thicknesses. The middle wall thickness may be less than the proximal and distal wall thicknesses and the distal wall thickness may be less than the proximal wall thickness. Additionally or alternatively, the shaft may comprise an inner cylindrical structure and an outer tube. The outer tube may comprise a first radial layer and a second radial layer that is radially-outward of the first radial layer, the first radial layer, second radial layer, and inner structure having different stiffnesses.

[0009] US Patent Application Publication 2002 / 0183817 to Van Venrooij et al. describes a directional brain stimulation lead assembly that provides a lead body and an insulating member defining one or more windows that selectively expose portions of electrodes carried by the lead body to produce a directional stimulation current field. The lead assembly can achieve more effective localization of electrical stimulation to very small brain targets, and thereby reduce the incidence of material side effects caused by collateral stimulation of brain tissue adjoining a desired brain target. In addition, the directional lead can sense brain activity on a more localized basis.

[0010] PCT Publication WO 2013 / 013098 to Cox et al. describes a catheter system and a method for creating Cox maze lesions in the heart.

[0011] US Patent 7,575,566 to Scheib describes a catheter as particularly useful for ablation lesions within a tubular region of or near the heart. The catheter comprises an elongated flexible tubular catheter body having an axis and proximal and distal ends. An ablation assembly is mounted at the distal end of the tubular body. The ablation assembly has a preformed generally circular curve having an outer surface and being generally transverse to the axis of the catheter body. The ablation assembly comprises a flexible tubing having proximal and distal ends that carries a tip electrode at its distal end. An electrode lead wire extends through the catheter body and into the ablation assembly and has a distal end connected to the tip electrode. In use, the distal end of the catheter is inserted into the heart of a patient. At least a portion of the outer circumference of the generally circular curve is contacted with the inner circumference of the tubular region so that the tip electrode is in a first position in contact with tissue along the inner circumference. The tip electrode is used to ablate tissue at the first position. The ablation assembly can then be rotated so that the tip electrode is in a second position in contact with tissue along the inner circumferencedifferent from the first position, and the tip electrode is used to ablate tissue at the second position. This procedure can be repeated to form a lesion of the desired length along the inner circumference.

[0012] US Patent Application Publication 2002 / 0022839 to Stewart et al. describes a catheter assembly and method for treatment of cardiac arrhythmia, for example, atrial fibrillation, by electrically isolating a vessel, such as a pulmonary vein, from a chamber, such as the left atrium. The catheter assembly includes a catheter body and at least one electrode. The catheter body includes a proximal portion, an intermediate portion and a distal portion. The intermediate portion extends from the proximal portion and defines a longitudinal axis. The distal portion extends from the intermediate portion and forms a substantially closed loop transverse to the longitudinal axis. The at least one electrode is disposed along the loop. With this configuration, the loop is axially directed into contact with the chamber wall about the vessel ostium. Upon energization, the electrode ablates a continuous lesion pattern about the vessel ostium, thereby electrically isolating the vessel from the chamber.

[0013] SUMMARY OF THE APPLICATION

[0014] Some embodiments of the present invention provide an electrode design for Pulsed Field Ablation (PF A) or thermal ablation (e.g., radiofrequency (RF) ablation). The electrode design may feature a Gaussian-shaped electrode, which delivers uniform electric fields for precise ablation while minimizing collateral damage. The electrode design is typically independent of catheter construction and may optimize energy delivery for myocardial tissue ablation. The electrode design may be used, for example, for treating cardiac arrhythmias, such as atrial arrhythmias (e.g., atrial fibrillation (AF)) or ventricular arrhythmias.

[0015] There is therefore provided, in accordance with an application of the present invention, an ablation catheter including:

[0016] a shaft including a distal electrode-support portion, the distal electrode-support portion having a central longitudinal axis defined by centroids of the distal electrodesupport portion along the distal electrode-support portion, wherein the distal electrodesupport portion includes electrical insulation; andan electrically-conductive electrode, which includes (a) an uninsulated electrode surface disposed on an outer surface of the distal electrode-support portion, and (b) an insulated electrode surface, wherein the electrical insulation insulates the insulated electrode surface with respect to outside the distal electrode-support portion, wherein the insulated electrode surface is shaped so as to define one or more curved surface portions that face only partially radially outward, and do not face even partially radially inward, with respect to the central longitudinal axis of the distal electrode-support portion, and

[0017] wherein for each of all points on the one or more curved surface portions, a line, which is (a) perpendicular to the central longitudinal axis and (b) intersects the central longitudinal axis and the point, defines an oblique angle with the curved surface portion at the point.

[0018] For some applications, the distal electrode-support portion is circular in crosssection perpendicular to the central longitudinal axis, and the central longitudinal axis is defined by centers of the distal electrode-support portion along the distal electrode-support portion.

[0019] For some applications, a ratio of a surface area of the uninsulated electrode surface to an aggregate surface area of the one or more curved surface portions is l.5:l to 3:l.

[0020] For some applications, at least a portion of outward-facing unit normal vectors to the one or more curved surface portions include non-zero vector components parallel to the central longitudinal axis.

[0021] For some applications, at least one of the one or more curved surface portions has an average radius of curvature of at least 0.25 mm. For some applications, the average radius of curvature is at least 0.35 mm. For some applications, the average radius of curvature is at least 0.5 mm.

[0022] For some applications, at least one of the one or more curved surface portions includes at least one curved-surface sub-portion having a radius of curvature of at least 0.25 mm. For some applications, the radius of curvature is at least 0.35 mm. For some applications, the radius of curvature is at least 0.5 mm.For some applications, the one or more curved surface portions include a plurality of curved surface portions, and the plurality of curved surface portions have respective average radii of curvature, each of which is at least 0.25 mm.

[0023] For some applications, at least one of the one or more curved surface portions has an average radius of curvature equal to at least 20% of a radius of the distal electrodesupport portion. For some applications, the average radius of curvature equals at least 30% of the radius of the distal electrode-support portion.

[0024] For some applications, at least 90% of a surface area of an entirety of a surface of the electrode is curved. For some applications, at least 95% of the surface area the entirety of the surface of electrode is curved.

[0025] For some applications:

[0026] a surface of the electrode includes:

[0027] at one of the following surface portions least: a first surface portion that faces entirely radially outward and a second surface portion that faces entirely radially inwardly, and

[0028] remaining surface portions of the electrode other than the first and the second surface portions, and

[0029] at least 90% of a surface area of the remaining surface portions is curved.

[0030] For some applications, at least 95% of the surface area of the remaining surface portions is curved.

[0031] For some applications, the uninsulated electrode surface is annular.

[0032] For some applications, the uninsulated electrode surface is not annular.

[0033] For some applications, the uninsulated electrode surface circumscribes 10 - 270 degrees of the central longitudinal axis.

[0034] For some applications, the uninsulated electrode surface circumscribes 10 - 180 degrees of the central longitudinal axis. For some applications, the uninsulated electrode surface circumscribes 10 - 90 degrees of the central longitudinal axis.

[0035] For some applications, the electrode circumscribes 10 - 270 degrees of the central longitudinal axis. For some applications, the electrode circumscribes 10 - 180 degrees ofthe central longitudinal axis. For some applications, the electrode circumscribes 10 - 90 degrees of the central longitudinal axis.

[0036] For some applications, an outermost perimeter of the electrode is elliptical.

[0037] For some applications, the outermost perimeter of the electrode is circular.

[0038] For some applications, an outermost perimeter of the electrode is shaped as a rounded rectangle.

[0039] For some applications, the rounded rectangle is a rounded square.

[0040] For some applications, the rounded rectangle is a squircle.

[0041] For some applications, an outermost perimeter of the electrode is shaped as a superellipse.

[0042] For some applications, the uninsulated electrode surface is convex as viewed from outside the distal electrode-support portion.

[0043] For some applications, the uninsulated electrode surface includes a planar portion. For some applications, an entirety of the uninsulated electrode surface is planar. For some applications, the insulated electrode surface defines a surface that faces radially inward and is concave as viewed from the central longitudinal axis.

[0044] For some applications, the insulated electrode surface defines a surface that faces radially inward and includes a planar portion.

[0045] For any of the applications described above, at least a portion of outward-facing unit normal vectors to the one or more curved surface portions, at respective points on the one or more curved surface portions, may include non-zero vector components that are (i) in a plane perpendicular to the central longitudinal axis and (ii) perpendicular to respective lines that are (a) perpendicular to the central longitudinal axis and (b) intersect the central longitudinal axis and the respective points.

[0046] For any of the applications described above, at least a portion of outward-facing unit normal vectors to the one or more curved surface portions, at respective points on the one or more curved surface portions, may include both:

[0047] non-zero vector components parallel to the central longitudinal axis, andnon-zero vector components that are (i) in a plane perpendicular to the central longitudinal axis and (ii) perpendicular to respective lines that are (a) perpendicular to the central longitudinal axis and (b) intersect the central longitudinal axis and the respective points.

[0048] For any of the applications described above:

[0049] at least a first portion of outward-facing unit normal vectors to the one or more curved surface portions, at respective points on the one or more curved surface portions, may include non-zero vector components parallel to the central longitudinal axis,

[0050] at least a second portion of outward-facing unit normal vectors to the one or more curved surface portions, at respective points on the one or more curved surface portions, may include non-zero vector components that are (i) in a plane perpendicular to the central longitudinal axis and (ii) perpendicular to respective lines that are (a) perpendicular to the central longitudinal axis and (b) intersect the central longitudinal axis and the respective points,

[0051] the first portion of the outward-facing unit normal vectors includes at least some points on the one or more curved surface portions that are not included in the second portion of the outward-facing unit normal vectors, and

[0052] the second portion of the outward-facing unit normal vectors includes at least some points on the one or more curved surface portions that are not included in the first portion of the outward-facing unit normal vectors.

[0053] For some applications, the first and the second portions include some of the same points on the one or more curved surface portions.

[0054] For any of the applications described above, the shaft may be tubular and may be shaped to define one or more lumens.

[0055] There is further provided, in accordance with an application of the present invention, an ablation system including the ablation catheter any of the applications described above, and further including an energy source. For some applications, the energy source is configured to apply pulsed field ablation energy. For some applications, the energy source is configured to apply radiofrequency (RF) ablation energy.There is still further provided, in accordance with an application of the present invention, a method including ablating tissue using the ablation catheter according to any one of the applications described above.

[0056] There is additionally provided, in accordance with an application of the present invention, an ablation catheter for treating atrial arrhythmia, including:

[0057] an elongate proximal shaft; and

[0058] a distal electrode-support portion, which includes:

[0059] an elongate distal shaft that includes a first shaft portion, a second shaft portion, and a shaft connecting end portion that connects a distal end of the first shaft portion to a proximal end of the second shaft portion; and

[0060] one or more ablation electrodes, which are configured to ablate an atrial wall of a heart, and which are at least partially disposed along the second shaft portion, wherein, when the distal electrode-support portion is unconstrained:

[0061] the first and the second shaft portions are entirely straight and the shaft connecting end portion is entirely curved,

[0062] the second shaft portion defines a distal end,

[0063] a central longitudinal axis of the first shaft portion is parallel to, or defines an angle of less than 10 degrees with, a central longitudinal axis of the second shaft portion,

[0064] the second shaft portion is longer than the first shaft portion, and the first shaft portion runs alongside only an axial portion of the second shaft portion, and the ablation catheter defines a catheter curved portion that connects a proximal end of the first shaft portion to a distal end of the elongate proximal shaft. For some applications, when the distal electrode-support portion is unconstrained: (a) a best-fit plane defined by the first and the second shaft portions forms a planeaxis angle with (b) a proximal -shaft central longitudinal axis of the elongate proximal shaft that passes through the distal end of the elongate proximal shaft, and the plane-axis angle is 45 - 135 degrees, e.g., 60 - 120 degrees, such as 75 - 105 degrees, e.g., 90 degrees.

[0065] For some applications, when the distal electrode-support portion is unconstrained: the elongate proximal shaft defines a proximal -shaft central longitudinal axis that passes through the distal end of the elongate proximal shaft,

[0066] the first and the second shaft portions define a best-fit plane, andthe proximal-shaft central longitudinal axis lies in the best-fit plane or defines a plane-axis angle with the best-fit plane, the plane-axis angle greater than 150 degrees.

[0067] For some applications, when the distal electrode-support portion is unconstrained, the proximal-shaft central longitudinal axis lies in the best-fit plane.

[0068] For some applications, when the distal electrode-support portion is unconstrained, the proximal-shaft central longitudinal axis defines the plane-axis angle with the best-fit plane, the plane-axis angle greater than 165 degrees.

[0069] For some applications, when the distal electrode-support portion is unconstrained, (a) the central longitudinal axis of the first shaft portion intersects and forms an axis-axis angle with (b) the proximal-shaft central longitudinal axis, the axis-axis-angle is 45 - 135 degrees, e.g., 60 - 120 degrees, such as 75 - 105 degrees, e.g., 90 degrees.

[0070] For some applications, the one or more ablation electrodes include two or more ablation electrodes disposed along the second shaft portion.

[0071] For some applications, when the distal electrode-support portion is unconstrained, the shaft connecting end portion has a radius of curvature of 0.25 cm - 3 cm, e.g., 0.25 cm - 1 cm.

[0072] For some applications, when the distal electrode-support portion is unconstrained, the elongate distal shaft has greatest major and minor dimensions perpendicular to each other, measured in a best-fit plane defined by the first and the second shaft portions, and the greatest major dimension equals at least 3 times the greatest minor dimension, e.g., at least 4 times the greatest minor dimension.

[0073] For some applications, the first and the second shaft portions are coplanar when the distal electrode-support portion is unconstrained.

[0074] For some applications, the central longitudinal axis of the first shaft portion is parallel to, or defines an angle of less than 10 degrees with, the central longitudinal axis of the second shaft portion,

[0075] For some applications, the central longitudinal axis of the first shaft portion is parallel to the central longitudinal axis of the second shaft portion, when the distal ablation probe is unconstrained.

[0076] For some applications, the first shaft portion has a length of 1 - 3 cm when the distalelectrode-support portion is unconstrained. For some of these applications, the second shaft portion has a length of 2 - 6 cm when the distal electrode-support portion is unconstrained.

[0077] For some applications, the second shaft portion has a length of 2 - 6 cm when the distal electrode-support portion is unconstrained.

[0078] For some applications, when distal electrode-support portion is unconstrained, the first shaft portion has a length that equals 1 - 3 times a closest distance between the first and the second shaft portions.

[0079] For some applications, a closest distance between the first and the second shaft portions is 5 - 30 mm when the distal electrode-support portion is unconstrained.

[0080] For some applications, when the distal electrode-support portion is unconstrained, the distal end of the second shaft portion is separate from the first shaft portion.

[0081] For some applications, when the distal electrode-support portion is unconstrained, the distal end of the second shaft portion is greater than 2 cm from the first shaft portion.

[0082] For some applications, when the distal electrode-support portion is unconstrained, the distal end is free.

[0083] For some applications, when the distal electrode-support portion is unconstrained, (a) the central longitudinal axis of the first shaft portion intersects and forms an axis-axis angle with (b) a proximal-shaft central longitudinal axis of the elongate proximal shaft that passes through the distal end of the elongate proximal shaft, and the axis-axis-angle is 45 -135 degrees, e.g., 60 - 120 degrees, such as 75 - 105 degrees, e.g., 90 degrees.

[0084] For some applications, the one or more ablation electrodes are disposed entirely along the second shaft portion.

[0085] For some applications, an entirety of the first shaft portion runs alongside the axial portion of the second shaft portion, when the distal electrode-support portion is unconstrained.

[0086] For some applications, when the distal electrode-support portion is unconstrained, a length of the second shaft portion is at least 1.5 times a length of the first shaft portion.

[0087] For some applications, when the distal electrode-support portion is unconstrained, the length of the second shaft portion is no more than 3 times the length of the first shaft portion.For some applications, a difference between a length of the first shaft portion and a length of the second shaft portion is 1 - 3 cm when the distal electrode-support portion is unconstrained.

[0088] For some applications, the distal electrode-support portion includes a shape memory material that causes the elongate distal shaft to define the first and the second straight shaft portions running alongside each other and the entirely curved shaft connecting end portion, when the elongate distal shaft is unconstrained.

[0089] For some applications, an ablation system is provided that includes the ablation catheter and further includes an intravascular delivery sheath, in which the ablation catheter is removably disposed for delivery such that the elongate distal shaft is constrained by the intravascular delivery sheath, such that the first and the second shaft portions are disposed at respective, non-longitudinally-overlapping locations along the intravascular delivery sheath.

[0090] For some applications, the ablation system further including an energy source. For some applications, the energy source is configured to apply pulsed field ablation energy. For some applications, the energy source is configured to apply radiofrequency (RF) ablation energy.

[0091] The present invention will be more fully understood from the following detailed description of embodiments thereof, taken together with the drawings, in which:

[0092] BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Figs. 1A-D are schematic illustrations of respective configurations of an ablation system for treating atrial arrhythmias, such as atrial fibrillation or atrial flutter, in accordance with respective applications of the present invention;

[0094] Figs. 2A-C are schematic illustrations of respective configurations of a distal electrode-support portion of the configurations of an ablation catheter of the ablation systems shown in Figs. 1A-C, respectively, in accordance with respective applications of the present invention;

[0095] Figs. 2D and 2E are schematic illustrations of the distal electrode-support portion of the configuration shown in Figs. 1C and 2C, from distal and side views, respectively, in accordance with an application of the present invention;Figs. 2F-H are schematic illustrations of the distal electrode-support portion of the configuration shown in Fig. ID, in accordance with an application of the present invention;

[0096] Figs. 3 A-B and 3C are schematic isometric and end-view illustrations, respectively, of an axial segment of a distal electrode-support portion of the ablation catheter of Figs.

[0097] 1 A-D, in accordance with an application of the present invention;

[0098] Figs. 4A-B are schematic cross-sectional views of the axial segment of the distal electrode-support portion of Figs. 3 A-C taken along line IVA — IVA, IVB — IVB of Fig.

[0099] 3 A, in accordance with an application of the present invention;

[0100] Fig. 5 A is a schematic illustration of a portion of the distal electrode-support portion of Figs. 3 A-C, in accordance with an application of the present invention;

[0101] Fig. 5B is a schematic illustration of an electrode of the distal electrode-support portion of Figs. 3 A-C, in accordance with an application of the present invention;

[0102] Fig. 6 is a schematic illustration of a portion of the distal electrode-support portion of Figs. 3 A-C, in accordance with an application of the present invention;

[0103] Figs. 7A and 7B are schematic isometric and cross-sectional illustrations of a portion of a distal electrode-support portion, in accordance with an application of the present invention;

[0104] Figs. 8A-B and 9A-B are schematic illustrations of alternative shapes of an electrode, in accordance with respective applications of the present invention; and Figs. 10A-F are schematic illustrations of a method for treating atrial arrhythmia, in accordance with an application of the present invention.

[0105] DETAILED DESCRIPTION OF APPLICATIONS

[0106] Some applications of the present invention provide a pulsed field ablation (PF A) or thermal ablation (e.g., radiofrequency (RF) ablation) electrode that can create consistent and predictable lesion shapes in cardiac tissue for the treatment of atrial arrhythmias, such as atrial fibrillation (AF), atrial flutter, or atrial tachycardia, while also exhibiting reduced energy spillover into surrounding blood to limit damage to red blood cells during an ablation procedure.

[0107] Some applications of the present invention provide methods for performing a one-step hybrid tissue ablation. In some embodiments, the one-step hybrid tissue ablation cancomprise a one-step hybrid cardiac tissue ablation. Also provided herein are Gaussian electrode designs that can be used inter alia to perform the one-step hybrid tissue ablation described herein (e.g., ‘purpose built’ pulse field ablation (PF A) electrodes). A one-step hybrid tissue ablation approach described herein is expected to be more effective, efficient, and precise than existing approaches.

[0108] In the following description, certain specific details are set forth to provide a thorough understanding of various embodiments. However, one skilled in the art will understand that the embodiments provided may be practiced without these details. Headings provided herein are for convenience only and do not interpret the scope or meaning of the claimed embodiments. Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is, as “including, but not limited to.”

[0109] As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description and / or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.”

[0110] As used herein, the phrases “at least one”, “one or more”, and “and / or” are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C”, “at least one of A, B, or C”, “one or more of A, B, and C”, “one or more of A, B, or C” and “A, B, and / or C” means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together.

[0111] As used herein, “or” may refer to “and”, “or,” or “and / or” and may be used both exclusively and inclusively. For example, the term “A or B” may refer to “A or B”, “A but not B”, “B but not A”, and “A and B”. In some cases, context may dictate a particular meaning. The term “about” or “approximately” refers to an amount that is near the stated amount by 10% or less.

[0112] The devices and methods described herein can provide a tailored approach to PFA procedures, RF procedure, and combined PFA / RF procedures. A "one-step" hybrid ablation procedure can combine multiple treatment modalities within a single system, which canallow for precise and efficient ablation of targeted tissues. A hybrid system is provided herein that can be used to perform a one-step hybrid ablation procedure. In some embodiments, a first ablation catheter can be employed to one side of a target tissue while a second ablation catheter is employed to the opposite side of a target tissue. The hybrid system can allow for precise coordination of energy delivery to both the inner and outer layers of a tissue (e.g., myocardium), allowing for uniform lesion depth and consistency. In some embodiments, under-treatment of critical areas of target tissue can be avoided by utilizing the hybrid system. In some embodiments, the hybrid system enables precise coordination of energy delivery to both the inner and outer layers of the myocardium, ensuring uniform lesion depth and consistency. In some embodiments, utilizing the hybrid system reduces the need for repeat procedures to effectively treat a target tissue.

[0113] In some embodiments, the tissue is a cardiac tissue. In some embodiments, the hybrid system is used to treat atrial arrhythmia in a subject, such as atrial fibrillation, atrial flutter, or atrial tachycardia.

[0114] In some embodiments, the first ablation catheter comprises a first electrode, which is placed on the epicardial surface of a target cardiac tissue for performing epicardial ablation, and the second ablation catheter comprises a second electrode, which is placed on the endocardial surface of the target cardiac tissue for performing endocardial ablation. By integrating both endocardial and epicardial ablation, this hybrid approach can provide a full lesion to the target cardiac tissue. In some embodiments, performing the endocardial and epicardial ablations simultaneously enhances the likelihood of achieving a durable transmural lesion in the target tissue. A durable transmural lesion can reduce the risk of arrhythmia recurrence and may offer improved patient outcomes compared to traditional stepwise or single-modality procedures. The first and the second electrodes may, for example, be first and second PFA electrodes or first and second RF electrodes.

[0115] The simultaneous use of endocardial and epicardial ablation may allow for lower overall energy delivery, which minimizes the risk of collateral damage to surrounding tissues such as the esophagus or phrenic nerve.

[0116] Gauss’s Law may dictate that sharp edges concentrate current density for PFA. In some embodiments, the PFA electrode comprises a design configured to reduce the number of sharp edges on the electrode (e.g., a Gaussian electrode). In some embodiments, the PFA electrode comprises a pill- or hemoglobin-shaped electrode. In some embodiments, the pill-or hemoglobin-shaped electrode is embedded in the catheter with only tissue facing surface area exposed. In some embodiments, the PFA electrode comprises a shielding layer opposite of a tissue facing surface area, which enhances layer-specific ablation by confining energy to a tissue layer (e.g., myocardial layer) and reducing collateral exposure (e.g., surrounding epicardium and red blood cells).

[0117] In some embodiments, the PFA or RF electrode comprises a Gaussian electrode. In some embodiments, the Gaussian electrode comprises a smoothed edge electrode geometry. In some embodiments, the Gaussian electrode can effectively create lesions in target tissue and can be configured to cause reduced damage to the surrounding red blood cells and nontarget tissue. In some embodiments, the Gaussian electrode is embedded in the catheter with only tissue facing surface area exposed. In some embodiments, the Gaussian electrode comprises a shielding layer opposite of a tissue facing surface area, which enhances layerspecific ablation by confining energy to a tissue layer (e.g., myocardial layer) and reducing collateral exposure (e.g., surrounding epicardium and red blood cells). The Gaussian electrode can be configured to deliver a Gaussian electric field to a biological tissue (e.g., a cardiac tissue, such as an atrial wall tissue). The Gaussian electrode can be shielded on one or more sides. In some embodiments, a shielded electrode is configured to ablate a target tissue while causing less damage to non-target tissue or surrounding red blood cells. Shielded electrodes can significantly enhance layer-specific ablation by confining energy to the myocardial layer and reducing collateral exposure to epicardium and blood for improved ablation precision.

[0118] In some embodiments, the Gaussian electrode conveys energy to a tissue using a Gaussian electric field.

[0119] In some embodiments, the Gaussian electrode comprises magnets for aligning the Gaussian electrode along a target tissue. In some embodiments, magnets on the first and the second PFA electrode can align the first and second PFA electrode along the target tissue.

[0120] In some embodiments, the above-mentioned first and second ablation catheters are magnetically attracted to each other through the atrial wall. For example, both ablation catheters may comprise respective sets of one or more magnets. Alternatively, one of the ablation catheters may comprise a set of one or more magnets and the other ablation catheter may comprise a ferromagnetic materials (that has not been permanently magnetized).In some of these embodiments, the magnetism of the first and the second ablation catheters is arranged to align the distal ends of the ablation catheters. For other applications, the magnetism may be arranged to align the distal end of one of the catheters with a more proximal portion of the other catheter away from its distal end.

[0121] Figs. 1 A-9B show exemplary electrode shapes that may be considered examples of the Gaussian electrodes described herein.

[0122] Reference is now made to Figs. 1A-D, which are schematic illustrations of respective configurations of an ablation system 10 for treating atrial arrhythmias, such as atrial fibrillation, atrial flutter, or atrial tachycardia, in accordance with respective applications of the present invention. Ablation system 10 comprises an ablation catheter 20.

[0123] Ablation catheter 20 typically comprises a shaft 22, which is typically, but not necessarily, tubular, and which comprises a distal electrode-support portion 26; and at least one electrically-conductive electrode 24, such as a plurality of electrodes 24, e.g., two - 12 electrodes 24. For example, the plurality of electrodes 24 may be arranged longitudinally along distal electrode-support portion 26 with inter-electrode spacing of 3 - 10 mm, e.g., 5 - 10 mm.

[0124] Although the description hereinbelow relates to a single one of electrodes 24, all of electrodes 24 may optionally have the features described.

[0125] For some applications, electrodes 24 face generally in one direction, so that the electrodes can be used to apply ablation energy primarily to cardiac tissue, rather than to blood in the cardiac chamber, thereby causing less damage to non-target tissue or surrounding red blood cells, and reducing hemolysis risk.

[0126] Reference is still made to Figs. 1 A-D, and is further made to Figs. 2A-H, which are schematic illustrations of respective configurations of distal electrode-support portion 26 of the configurations of ablation catheter 20 shown in Figs. 1 A-C, respectively, in accordance with respective applications of the present invention. Figs. 2D and 2E are schematic illustrations of distal electrode-support portion 26 of the configuration shown in Figs. 1C and 2C, from distal and side views, respectively, in accordance with an application of the present invention. Figs. 2F-H are schematic illustrations of distal electrode-support portion 26 of the configuration shown in Fig. ID, in accordance with an application of the presentinvention. Alternatively, distal electrode-support portion 26 may have another shape, such as a basket shape, a spiral shape, a helical shape, or a lasso shape.

[0127] Distal electrode-support portion 26 has a central longitudinal axis 28 defined by centroids of distal electrode-support portion 26 along distal electrode-support portion 26. Central longitudinal axis 28 may include straight and / or curved portions. In Figs. 1 A and 2A, central longitudinal axis 28 is shown as including only a straight portion. In Figs. IB and 2B, central longitudinal axis 28 is shown as including three straight portions and two curved portions; optionally, the three straight portions are oriented parallel to one another, such as shown. In Figs. 1C-D and 2C-H, central longitudinal axis 28 is shown as including two straight portions and one curved portion; optionally, the two straight portions are oriented parallel to each other, such as shown. Typically, but not necessarily, each of electrodes 24 is disposed along a straight portion of central longitudinal axis 28, such as shown. Additional detail regarding optional features of the configurations of Figs. 1C-D and 2C-H is described hereinbelow with reference to Figs. 2D-H.

[0128] For some applications, such as illustrated, distal electrode-support portion 26 is circular in cross-section perpendicular to central longitudinal axis 28, and central longitudinal axis 28 is defined by centers of distal electrode-support portion 26 along distal electrode-support portion 26. Alternatively, distal electrode-support portion 26 has another cross-sectional shape, such as, for example, an ellipse.

[0129] For some applications, ablation system 10 further comprises an energy source 35, which may comprise a non-thermal energy source, such as a pulsed field ablation energy source, as is known in the art. Alternatively, energy source 35 may comprise a thermal energy source, such as a radiofrequency (RF) power source. Typically, ablation system 10 further comprises an operator handle, as is known in the art, and, optionally, an umbilical connector, as is known in the art.

[0130] Reference is still made to Figs. 1 A-D and 2A-H, and is further made to Figs. 3A-B and 3C, which are schematic isometric and end-view illustrations, respectively, of an axial segment of distal electrode-support portion 26, in accordance with an application of the present invention.Reference is additionally made to Figs. 4A-B, which are schematic cross-sectional views of the axial segment of distal electrode-support portion 26 taken along line IVA — IVA, IVB — IVB of Fig. 3 A, in accordance with an application of the present invention.

[0131] Reference is yet additionally made to Fig. 5A, which is a schematic illustration of a portion of distal electrode-support portion 26, in accordance with an application of the present invention.

[0132] Reference is also made to Fig. 5B, which is a schematic illustration of electrode 24, in accordance with an application of the present invention.

[0133] Reference is further made to Fig. 6, which is a schematic illustration of a portion of distal electrode-support portion 26, in accordance with an application of the present invention.

[0134] Distal electrode-support portion 26 comprises electrical insulation 30. Electrical insulation 30 may be provided by:

[0135] • the material of a wall 32 of distal electrode-support portion 26; for example, the material of wall 32 may comprise a polymer, such as a thermoplastic elastomer (TPE) (e g., PEBA),

[0136] • insulating potting 34, which helps mount electrode 24 to distal electrode-support portion 26; for example, insulating potting 34 may comprise an epoxy adhesive or a UV-cured adhesive, or

[0137] • a combination of the material of wall 32 and insulating potting 34, such as shown in the figures.

[0138] In Figs. 3A and 4A-B, insulating potting 34 is illustrated as solid, while in Fig. 3B (as well as in Figs. 5A and 6), insulating potting 34 is illustrated as transparent, for clarity of illustration.

[0139] Electrode 24 comprises:

[0140] • an uninsulated electrode surface 40 disposed on an outer surface 42 of distal electrode-support portion 26 (flush with surface 42, as shown; slightly protruding from surface 42; or slightly recessed in surface 42); and

[0141] • an insulated electrode surface 44.Together, uninsulated electrode surface 40 and insulated electrode surface 44 define an entirety of the surface of electrode 24. Electrical insulation 30 insulates insulated electrode surface 44 with respect to outside of distal electrode-support portion 26 (and thus with respect to the patient’s body when inserted into the body). Optionally, only a portion of insulated electrode surface 44 is embedded in electrical insulation 30 and / or potting 34, while another portion of insulated electrode surface 44 is disposed within a lumen 46 of distal electrode-support portion 26, such that wall 32 and / or potting 34 insulate insulated electrode surface 44 with respect to outside of distal electrode-support portion 26, such as shown in the figures. Alternatively, an entirety of insulated electrode surface 44 is embedded in electrical insulation 30 and / or potting 34 (configuration not shown).

[0142] For some applications, at least 90%, such as least 95%, e.g., 100%, of a surface area the entirety of the surface of electrode 24 is curved. (As mentioned above, uninsulated electrode surface 40 and insulated electrode surface 44 define the entirety of the surface of electrode 24.)

[0143] In some applications of the present invention, insulated electrode surface 44 is shaped so as to define one or more curved surface portions 50 that face only partially radially outward, and do not face even partially radially inward, with respect to central longitudinal axis 28 of distal electrode-support portion 26.

[0144] Typically, insulated electrode surface 44 is shaped so as to define, in addition to the above-mentioned one or more curved surface portions 50, (a) one or more curved surface portions that face partially radially inward, and / or (b) one or more curved surface portions that face entirely radially inward.

[0145] As used in the present application, “facing entirely radially outward” means facing entirely away from central longitudinal axis 28 of distal electrode-support portion 26. Thus, as illustrated in Fig. 6, for any point 52 on a curved surface 54 that faces entirely radially outward, an outward-facing unit normal vector 56 at point 52 will lie along a line 58 that is (a) perpendicular to central longitudinal axis 28 and (b) intersects central longitudinal axis 28 and point 52. Similarly, “facing entirely radially inwardly” means facing entirely toward central longitudinal axis 28 of distal electrode-support portion 26.

[0146] As used in the present application, including in the claims, also as illustrated in Fig.

[0147] 6, “facing only partially radially outward” means, for any point 60 on curved surface portion50 that faces only partially radially outward, a line 62, which is (a) perpendicular to central longitudinal axis 28 and (b) intersects central longitudinal axis 28 and point 60, defines an oblique angle alpha (a) with curved surface portion 50 at point 60. (In Fig. 6, for clarity of illustration, only three of many points 60 and lines 62 are illustrated, and line 62 and oblique angle alpha (a) are labeled only once.) Thus, an outward-facing unit normal vector 64 at point 60 includes a non-zero vector component 66 that faces entirely radially outward.

[0148] Because the one or more curved surface portions 50 of insulated electrode surface 44 are insulated with respect to the patient’s body by electrical insulation 30 of distal electrode-support portion 26, the curvature may have beneficial effects, including, for example:

[0149] • the curvature may avoid high electric fields that might be provided by sharp edges, which reduces edge effects (including sparking), including the risk that the applied current might damage and / or pass through electrical insulation 30;

[0150] • the curvature, by reducing the electric fields at the edges of the electrode, may provide a more uniform electric field on uninsulated electrode surface 40, which results in a more effective current density applied into the tissue; and / or

[0151] • the resulting improved efficiency may reduce unwanted skeletal muscle capture, which may allow more PFA procedures to be performed under conscious sedation, rather than the conventional general anesthesia.

[0152] For some applications, edge field intensities are at least 30% less than traditional ring electrodes.

[0153] It is noted that the one or more curved surface portions 50 of insulated electrode surface 44 do not provide any mechanically atraumatic features with respect to the patient’s body, because the one or more curved surface portions 50 are covered by electrical insulation 30 and thus do not come in mechanical contact with the patient’s body.

[0154] For some applications, a ratio of a surface area of uninsulated electrode surface 40 to an aggregate surface area of the one or more curved surface portions 50 is at least 1.5:1 (e.g., at least 2:1, such as at least 2.25:1), no more than 3:1, and / or 1.5:1 to 3:1, e.g., 2:1 -2.5:1, e.g., 2.25:1.For some applications, the surface of electrode 24 includes a first surface portion that faces entirely radially outward and / or a second surface portion that faces entirely radially inwardly, and remaining surface portions of electrode 24 other than the first and the second surface portions. For some of these applications, at least 90%, such as least 95%, e.g., 100%, of a surface area of the remaining surface portions is curved.

[0155] Reference is made to Figs. 3B, 5A, and 6. For some applications, as labeled in Fig.

[0156] 6, at least a portion of outward-facing unit normal vectors 64 to the one or more curved surface portions 50, 50A include non-zero vector components 68 parallel to central longitudinal axis 28. In other words, the one or more curved surface portions 50, 50A face at least partially parallel to central longitudinal axis 28. (In Fig. 6, for clarity of illustration, only one of many outward-facing unit normal vectors 64 and only one of many non-zero vector components 68 are labeled.)

[0157] Reference is made to Figs. 3B, 4A-B, 5A, and 6. For some applications, as labeled in Fig. 4B, at least a portion of outward-facing unit normal vectors 70 to the one or more curved surface portions 50, 50B, at respective points 72 on the one or more curved surface portions 50, 50B, include non-zero vector components 74 that are (i) in a plane 76 perpendicular to central longitudinal axis 28 and (ii) perpendicular to respective lines 78 that are (a) perpendicular to central longitudinal axis 28 and (b) intersect central longitudinal axis 28 and respective points 72. In other words, the one or more curved surface portions 50, 50B lie at least partially in planes tangential to outer surface 42 of distal electrode-support portion 26. (In Fig. 4B, for clarity of illustration, only one of many unit normal vectors 70, only one of many points 72, and only one of many non-zero vector components 74 are labeled.)

[0158] Reference is made to Figs. 3B, 5A, and 6. For some applications, at least a portion of outward-facing unit normal vectors to the one or more curved surface portions 50, 50C at respective points on the one or more curved surface portions 50, 50C include both:

[0159] • non-zero vector components parallel to central longitudinal axis 28, and

[0160] • non-zero vector components that are (i) in plane 76 perpendicular to central longitudinal axis 28 and (ii) perpendicular to respective lines 78 that are (a) perpendicular to central longitudinal axis 28 and (b) intersect central longitudinal axis 28 and the respective points.In other words, the one or more curved surface portions 50, 50C (a) face at least partially parallel to central longitudinal axis 28 and (b) lie at least partially in planes tangential to outer surface 42 of distal electrode-support portion 26.

[0161] For some applications:

[0162] • at least a first portion of outward-facing unit normal vectors 64 to the one or more curved surface portions 50, 50A, at respective points on the one or more curved surface portions 50, 50A, include non-zero vector components 68 parallel to central longitudinal axis 28, and

[0163] • at least a second portion of outward-facing unit normal vectors 70 to the one or more curved surface portions 50, 50B, at respective points 72 on the one or more curved surface portions 50, 50B, include non-zero vector components 74 that are (i) in plane 76 perpendicular to central longitudinal axis 28 and (ii) perpendicular to respective lines 78 that are (a) perpendicular to central longitudinal axis 28 and intersect central longitudinal axis 28 and respective points 72.

[0164] Typically, the first portion of outward-facing unit normal vectors 64 includes at least some points on the one or more curved surface portions 50 that are not included in the second portion of outward-facing unit normal vectors 70, and the second portion of outward-facing unit normal vectors 70 includes at least some points on the one or more curved surface portions 50 that are not included in the first portion of outward-facing unit normal vectors 64. Optionally, the first and the second portions include some of the same points on the one or more curved surface portions 50.

[0165] For some applications:

[0166] • at least one of the one or more curved surface portions 50 has an average radius of curvature (a) of at least 0.25 mm, such as at least 0.35 mm, e.g., at least 0.5 mm, (b) equal to at least 20%, such as at least 30%, e.g., at least 40%, of a radius of distal electrode-support portion 26, and / or (c) of 25% - 75%, such as 40% - 60%, e.g., 50%, of a radial thickness of electrode 24,

[0167] • at least one of the one or more curved surface portions 50 includes at least one curved-surface sub-portion having a radius of curvature (a) of at least 0.25 mm, such as at least 0.35 mm, e.g., at least 0.5 mm, and / or (b) equal to at least 20%, such as at least 30%, e.g., at least 40%, of a radius of distal electrode-support portion 26,and / or (c) of 25% - 75%, such as 40% - 60%, e.g., 50%, of a radial thickness of electrode 24, and / or

[0168] • the one or more curved surface portions 50 include a plurality of curved surface portions 50, and the plurality of curved surface portions 50 have respective average radii of curvature, each of which is at least 0.25 mm, such as at least 0.35 mm, e.g., at least 0.5 mm.

[0169] For some applications, such as shown in Figs. 1 A-6, uninsulated electrode surface 40 is convex as viewed from outside distal electrode-support portion 26.

[0170] For some applications:

[0171] • uninsulated electrode surface 40 circumscribes 10 - 270 degrees, such as 10 - 180 degrees, e.g., 10 - 90 degrees, of central longitudinal axis 28, such as of central longitudinal axis 28, and / or

[0172] • electrode 24 circumscribes 10 - 270 degrees, such as 10 - 180 degrees, e.g., 10 - 90 degrees, of central longitudinal axis 28.

[0173] For some applications, electrode 24 is has a shape generally similar to the shape of a red blood cell (albeit much larger).

[0174] For some applications, electrode 24 has one or more of the following dimensions:

[0175] • an axial length of 1.5 - 8.0 mm,

[0176] • a width of 0.5 - 3.5 mm,

[0177] • a length-to-width ratio of 2: 1 - 4:1, and / or

[0178] • a thickness 0.2 - 0.5 mm.

[0179] For some applications, electrode 24 comprises a biocompatible metal, e.g., platinum -iridium, gold, stainless steel. Alternatively or additionally, such as for applications in which ablation catheter 20 is configured as a first endocardial ablation catheter for use with a second epicardial ablation catheter, as described above, electrode 24 comprises a ferromagnetic material, which is optionally permanently magnetized.

[0180] For some applications, all junctions between non-congruent surfaces of electrode 24 have a continuous radius of curvature, ensuring uniform energy propagation.Reference is made to Figs. 3A-C and 4A-B. Typically, tubular shaft 22 of ablation catheter 20 is shaped so as to define one or more lumens. By way of example and not limitation, the two smaller illustrated lumens may be configured to house two different stylet shapes (e.g., one for pulmonary vein isolation (PVI) ablation and one for linear ablation), and the larger lumen may be configured to house electrodes 24, wiring, and, optionally, a ferromagnetic material, which is optionally permanently magnetized.

[0181] For some applications, such labeled in Figs. 3C, 4A-B, and 5B, insulated electrode surface 44 defines a surface 94 that faces radially inward and is concave as viewed from central longitudinal axis 28. For example, this internal concavity may provide more space for internal wires in the catheter lumen.

[0182] Reference is now made to Figs. 7A and 7B, which are schematic isometric and cross-sectional illustrations of a portion of a distal electrode-support portion 126, in accordance with an application of the present invention. Distal electrode-support portion 126 may be implemented instead of distal electrode-support portion 26, described herein with reference to Figs. 1 A-6, and an ablation catheter comprising distal electrode-support portion 126 may implement any of the features of ablation catheter 20 described herein.

[0183] In this configuration, uninsulated electrode surface 40 is annular. For some applications, as labeled in Fig. 7B, at least a portion of outward-facing unit normal vectors 64 to the one or more curved surface portions 50, 50A include non-zero vector components 68 parallel to central longitudinal axis 28. In other words, the one or more curved surface portions 50, 50A face at least partially parallel to central longitudinal axis 28.

[0184] Reference is now made to Figs. 8A-B and 9A-B, which are schematic illustrations of alternative shapes of electrode 24, in accordance with respective applications of the present invention. For some applications, such as shown in Figs. 8A-B, an outermost perimeter 90 of electrode 24 is elliptical, such as circular (as shown). For other applications, such as shown in Figs. 9A-B, outermost perimeter 90 of electrode 24 is shaped as a rounded rectangle, such as a rounded square (as shown). For still other applications (configurations not shown), outermost perimeter 90 of electrode 24 is shaped as a superellipse, such as a squircle.For some applications, such as shown in Figs. 8A-B and 9A-B, uninsulated electrode surface 40 includes a planar portion 92. For some of these applications, an entirety of uninsulated electrode surface 40 is planar.

[0185] For some applications, such as shown in Figs. 8A-B and 9A-B, insulated electrode surface 44 defines a surface that faces radially inward and includes a planar portion.

[0186] For some applications, such as shown in Figs. 8A-B and 9A-B, electrode 24 is shaped so as to define a front face and a back face, which are mutually connected by a perimeter wall. A junction between the wall and front face is curved, and / or a junction between the wall and the back face is curved.

[0187] Reference is made to Figs. 1A-6 and 8A-9B. For some applications, uninsulated electrode surface 40 is not annular.

[0188] Reference is now made to Figs. 10A-F, which are schematic illustrations of a method for treating atrial arrhythmia, in accordance with an application of the present invention. Optionally, the method implements techniques described in US Patent Application Publication 2024 / 0268885 to Chambers, mutatis mutandis, including with reference to Figs. 4A-F thereof. The ‘8885 publication is incorporated herein by reference.

[0189] Fig. 10D shows the use of an epicardial lead 200 in combination with ablation catheter 20, such as described in detail hereinbelow with reference to Fig. 10D. This use of epicardial lead 200 is entirely optional in the techniques described herein.

[0190] In some embodiments, a single-step hybrid procedure minimizes the need for multiple interventions (e.g., a first ablation that is an epicardial ablation and a second ablation that is an endocardial ablation). Fewer procedures can reduce procedural complexity and the associated risks of sequential ablation sessions, including operator fatigue and the likelihood of procedural errors, which can provide for safer and more effective treatment. Combining procedures into a single session can also reduce the overall treatment time, hospitalization duration, and recovery period for the patient. The one-step hybrid method can also decrease the psychological and physical burden associated with multiple invasive procedures, improving patient satisfaction. In some embodiments, the hybrid approach streamlines procedural workflows by integrating diagnostic, mapping, and ablation steps into a unified system, which can reduce the need for equipment changes or repositioning, enhancing operational efficiency and lowering resource consumption in theclinical setting. By consolidating treatments into a single procedure, the hybrid ablation method can reduce cumulative procedural costs, including equipment use, personnel resources, and post-operative care. Over time, this approach can provide significant cost savings for healthcare providers while delivering superior care.

[0191] A “one-step” hybrid system can be inherently versatile, accommodating various patient anatomies and arrhythmia types. In some embodiments, the “one-step” hybrid system can be suitable for treating complex cases, including patients with extensive scar tissue or persistent atrial fibrillation, where single-modality approaches may be insufficient.

[0192] By consolidating treatments into a single procedure, the hybrid ablation method can reduce cumulative procedural costs, including equipment use, personnel resources, and post-operative care. Over time, this approach can provide significant cost savings for healthcare providers while delivering superior care.

[0193] EXAMPLE

[0194] The following illustrative example is representative of an embodiment of techniques described herein and is not meant to be limiting in any way.

[0195] Example: Exemplary pulse-field ablation (PEA) electrode for creating ablation lesion in target cardiac tissue

[0196] Reference is made to Fig. 10D. A hybrid catheter system can be employed for transformative ablation. The hybrid catheter system combines precision pulse field ablation (PF A) electrodes with a one-step hybrid approach. For treatment of atrial fibrillation, an epicardial lead 200 and endocardial ablation catheter 20 can be delivered to the left atrium of a subject, as depicted in Fig. 10D. The epicardial lead is depicted in a linear lesion position on the low posterior wall of an atrium of a heart in Fig. 10D.

[0197] Epicardial lead 200 comprises one or more epicardial electrodes and is configured to serve as a return catheter for PF A. By way of example and not limitation, endocardial ablation catheter 20 is shown in the configuration described hereinabove with reference to Figs. 1C and 2C. By way of example and not limitation, endocardial ablation catheter 20 is shown positioned such that it reaches from the right inferior pulmonary vein to the left inferior pulmonary vein. Typically mounted on endocardial ablation catheter 20 are 4-10, e.g., 6-10, electrodes 24, such as described hereinabove (which may be referred to as Gaussian electrodes), which optionally are evenly spaced, and which are configured todeliver an electric field to the cardiac tissue. The catheters can be magnetically attracted to each other for alignment, such as described above. The electrodes are configured to create a transmural lesion in the myocardium of the heart.

[0198] A potato model experiment was conducted to evaluate the electric field distribution, lesion formation, and depth uniformity of the Gaussian electrode design in a controlled ex vivo environment, validated against the methodology described in Nature Scientific Reports (2021, DOI:10.1038 / s41598-021-99987-2). Potatoes were chosen as the tissue model due to their established use in electroporation experiments, as highlighted in the referenced publication.

[0199] Following the validated protocol, the potatoes were submerged in a saline solution to simulate the ionic environment of biological tissues. Gaussian electrodes, integrated into a catheter-like setup, were connected to a pulsed field ablation generator programmed with calibrated pulse parameters consistent with the referenced study. The electrodes were positioned for consistent tissue contact, and after energy delivery, the potato samples were sliced cross-sectionally and stained with Lugol’s iodine solution, as described in the publication. This staining method distinguished ablated regions, which remained unstained, from non-ablated areas, which darkened due to the iodine interaction with starch. The stained sections were analyzed to assess lesion morphology, depth, and uniformity. Results from these experiments were compared to the findings in the referenced study, confirming the validity of the model and demonstrating that the Gaussian electrode design produced superior lesion uniformity and reduced edge effects compared to traditional designs.

[0200] Reference is made to Figs. 2D-H. In some applications of the present invention, an ablation catheter 320 is provided, typically for treating atrial arrhythmia. The features of ablation catheter 320 may be implemented in combination with any of the features of ablation catheter 20 described herein, including any of the electrode configurations described herein. Alternatively, the following configurations may be implemented in ablation catheters comprising ablation elements that differ from those described herein, such as electrodes that differ from those described herein, including any ablation elements, such as ablation electrodes, known in the art.

[0201] Ablation catheter 320 comprises an elongate proximal shaft 323 and a distal electrode-support portion 326. Distal electrode-support portion 326 comprises:• an elongate distal shaft 330 that includes a first shaft portion 332A, a second shaft portion 332B, and a shaft connecting end portion 334 that connects a distal end 336 of first shaft portion 332A to a proximal end 338 of second shaft portion 332B; and • one or more ablation electrodes 324, which are configured to ablate an atrial wall of a heart, and which are at least partially disposed along second shaft portion 332B; optionally, the one or more ablation electrodes 324 may implement any of the features of electrodes 24 described herein.

[0202] Reference is still made to Figs. 2D-H. For some applications, when distal electrodesupport portion 326 is unconstrained (including by an intravascular delivery sheath or the anatomy):

[0203] • first and second shaft portions 332 A and 332B are straight and shaft connecting end portion 334 is entirely curved; typically, first and second shaft portions 332A and 332B are entirely straight (and thus are not straight segments of longer shaft portions),

[0204] • second shaft portion 332B defines a distal end 340,

[0205] • a central longitudinal axis 342A of first shaft portion 332A is parallel to (as shown), or defines an angle of less than 10 degrees, e.g., less than 5 degrees, with (configuration not shown), a central longitudinal axis 342B of second shaft portion 332B,

[0206] • second shaft portion 332B is longer than first shaft portion 332A, and first shaft portion 332A runs alongside only an axial portion 344 of second shaft portion 332B, and

[0207] • ablation catheter 320 defines a catheter curved portion 346 that connects a proximal end 348 of first shaft portion 332A to a distal end 350 of elongate proximal shaft 323.

[0208] Reference is still made to Figs. 2D-H. Typically, when distal electrode-support portion 326 is unconstrained, distal end 340 of second shaft portion 332B is separate from first shaft portion 332A; for example, distal end 340 of second shaft portion 332B may be at a distance D4 from first shaft portion 332A, when distal electrode-support portion 326 isunconstrained, the distance D4 greater than 2 cm, e.g., greater than 3 cm. Optionally, distal end 340 is free, not connected to any other elements of ablation catheter 320, such as shown.

[0209] Optionally, elongate distal shaft 330 and / or elongate proximal shaft 323 comprises a plurality of pieces coupled together, which may or may not have the same cross-sectional shapes. For example, such as shown in Figs. 2F-G, elongate distal shaft 330 may comprise one or more magnets 360, such as a proximal magnet 360 A and a distal magnet 360B. For example, in applications in which ablation catheter 320 is an endocardial ablation catheter for use with an epicardial ablation catheter, the magnets may assist with aligning endocardial ablation catheter 320 with the epicardial ablation catheter. Optionally, at least one of magnets 360, such as proximal magnet 360A, is tubular; alternatively, for some applications, electrical leads run through tubular portions of elongate distal shaft 330 other than the at least one of magnets 360, and exist the shaft, run alongside the at least one magnet outside the magnet, and re-enter the shaft; in these applications, the magnet may be solid. More generally, elongate distal shaft 330 and / or elongate proximal shaft 323 may include one or more tubular portions and one or more non-tubular portions, disposed along elongate distal shaft 330 and / or elongate proximal shaft 323. Optionally, shaft 22 may implement any of the configurations described in this paragraph, and / or shaft 22 may include one or more tubular portions and one or more non-tubular portions, disposed along distal electrode-support portion 26 and / or along an elongate proximal shaft proximal to distal electrode-support portion 26.

[0210] Reference is still made to Figs. 2D-H. First and second shaft portions 332A and 332B a best-fit plane 352. Elongate proximal shaft 323 defines a proximal-shaft central longitudinal axis 354 that passes through distal end 350 of elongate proximal shaft 323.

[0211] For some applications, such as shown in Figs. 2D-E (and Fig. 1C), best-fit plane 352 forms a plane-axis angle P (beta) with proximal-shaft central longitudinal axis 354, and the plane-axis angle P (beta) is 45 - 135 degrees, such as 60 - 120 degrees, e.g., 75 - 105 degrees, such as 90 degrees.

[0212] For other applications, such as shown in Figs. 2F-H (and Fig. ID), proximal -shaft central longitudinal axis 354 lies in best-fit plane 352 or forms the plane-axis angle P (beta) with best-fit plane 352, the plane-axis angle P (beta) greater than 150 degrees, such as greater than 165 degrees, e.g., greater than 175 degrees.As used in the present application, including in the claims, a “central longitudinal axis” of a shaft is defined by centroids of the shaft along the shaft. A “central longitudinal axis” may include straight and / or curved portions.

[0213] Reference is made to Figs. 1B-2H. For some applications, the one or more ablation electrodes 324 surround less than 360 degrees, such as less than 270 degrees, e.g., less than 180 degrees of distal electrode-support portion 326. For some of these applications, the one or more ablation electrodes 324 face in a direction generally away from distal end 350 of elongate proximal shaft 323.

[0214] Reference is made to Figs. ID and 2F-G. For some applications, second shaft portion 332B comprises an atraumatic tip 362 that defines distal end 340 of second shaft portion 332B. In these applications, the length L2 of second shaft portion 332B, described hereinbelow, is measured until the end of tip 362. For example, tip 362 may be curved, such as semispherical, as shown.

[0215] Reference is again made to Figs. 2D-H. For some applications, the one or more ablation electrodes 324 are disposed entirely along second shaft portion 332B (such as shown). For some applications, the one or more ablation electrodes 324 comprise two or more ablation electrodes 324 disposed along second shaft portion 332B. In these configurations, distal electrode-support portion 326 may create a single elongate continuous ablation lesion segment. However, distal electrode-support portion 326 does not create two elongate continuous ablation lesion segments, because the one or more ablation electrodes 324 are disposed entirely along second shaft portion 332B, rather than also along first shaft portion 332A.

[0216] Alternatively, the one or more ablation electrodes 324 are disposed along both first and second shaft portions 332A and 332B (configuration not shown). In this configuration, distal electrode-support portion 326 may create two elongate continuous ablation lesion segments that are spaced apart. However, the two elongate continuous ablation lesion segments do not run alongside each other along the entire lengths of the lesion segments, because second shaft portion 332B is longer than first shaft portion 332A, and first shaft portion 332A runs alongside only an axial portion 344 of second shaft portion 332B.Reference is still made to Figs. 2D-H. For some applications, such as shown, an entirety of first shaft portion 332A runs alongside axial portion 344 of second shaft portion 332B, when distal electrode-support portion 326 is unconstrained.

[0217] Reference is still made to Figs. 2D-H. For some applications, when distal electrodesupport portion 326 is unconstrained, shaft connecting end portion 334 has a radius of curvature R of 0.25 cm - 3 cm, such as 0.25 cm - 1 cm.

[0218] For some applications, when distal electrode-support portion 326 is unconstrained, elongate distal shaft 330 has a greatest major dimension DI and a greatest minor dimension D2 perpendicular to each other, measured in best-fit plane 352, and the greatest major dimension DI equals at least 3 times the greatest minor dimension D2, such as at least 4 times the greatest minor dimension D2.

[0219] For some applications, first and second shaft portions 332A and 332B are coplanar (i.e., lie in a common plane) when distal electrode-support portion 326 is unconstrained.

[0220] Reference is still made to Figs. 2D-H. For some applications, distal electrodesupport portion 326, when unconstrained, has one or more of the following dimensions or relative dimensions:

[0221] • first shaft portion 332A has a length LI of 1 - 3 cm,

[0222] • second shaft portion 332B has a length L2 of 2 - 6 cm,

[0223] • the length L2 of second shaft portion 332B is at least 1.5 times (e.g., at least 2 times) and / or no more than 3 times (e.g., no more than 2.5 times) the length LI of first shaft portion 332A,

[0224] • a difference between the length LI of first shaft portion 332A and the length L2 of second shaft portion 332B is 1 - 3 cm,

[0225] • the length LI of first shaft portion 332A equals 1 - 3 times a closest distance D3 between first and second shaft portions 332A and 332B, and / or

[0226] • the closest distance D3 between first and second shaft portions 332A and 332B is 5 - 30 mm, such as 5 - 20 mm.

[0227] Reference is still made to Figs. 2D-H. For some applications, distal electrodesupport portion 326 comprises a shape memory material that causes elongate distal shaft330 to define the first and the second straight shaft portions 332A and 332B running alongside each other and the entirely curved shaft connecting end portion 334, when elongate distal shaft 330 is unconstrained.

[0228] Reference is still made to Figs. 2D-H. For some applications, when distal electrodesupport portion 326 is unconstrained, (a) central longitudinal axis 342A of first shaft portion 332A intersects and forms an axis-axis angle 5 (gamma) with (b) central longitudinal axis 354 of elongate proximal shaft 323, and the axis-axis-angle 5 (gamma) is 45 - 135 degrees, such 60 - 120 degrees, e.g., 75 - 105 degrees, such as 90 degrees.

[0229] For some applications, an ablation system is provided that comprises ablation catheter 320 and an intravascular delivery sheath, in which ablation catheter 320 is removably disposed for delivery such that elongate distal shaft 330 is constrained by the intravascular delivery sheath, such that first and second shaft portions 332A and 332B are disposed at respective, non-longitudinally-overlapping locations along the intravascular delivery sheath.

[0230] In an embodiment, techniques and apparatus described herein are combined with techniques and apparatus described in US Patent Application Publication 2024 / 0268885 to Chambers, mutatis mutandis, which is incorporated herein by reference. In particular, the configuration of ablation system 10 shown in Figs. IB and 2B and the configuration of ablation system 10 shown in Figs. 1C and 2C may implement any of the techniques and apparatus described in the ‘8885 publication, mutatis mutandis.

[0231] It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.

Claims

CLAIMS1. An ablation catheter comprising:a shaft comprising a distal electrode-support portion, the distal electrode-support portion having a central longitudinal axis defined by centroids of the distal electrodesupport portion along the distal electrode-support portion, wherein the distal electrodesupport portion comprises electrical insulation; andan electrically-conductive electrode, which comprises (a) an uninsulated electrode surface disposed on an outer surface of the distal electrode-support portion, and (b) an insulated electrode surface, wherein the electrical insulation insulates the insulated electrode surface with respect to outside the distal electrode-support portion, wherein the insulated electrode surface is shaped so as to define one or more curved surface portions that face only partially radially outward, and do not face even partially radially inward, with respect to the central longitudinal axis of the distal electrode-support portion, andwherein for each of all points on the one or more curved surface portions, a line, which is (a) perpendicular to the central longitudinal axis and (b) intersects the central longitudinal axis and the point, defines an oblique angle with the curved surface portion at the point.

2. The ablation catheter according to claim 1, wherein the distal electrode-support portion is circular in cross-section perpendicular to the central longitudinal axis, and the central longitudinal axis is defined by centers of the distal electrode-support portion along the distal el ectrode- support portion.

3. The ablation catheter according to claim 1, wherein a ratio of a surface area of the uninsulated electrode surface to an aggregate surface area of the one or more curved surface portions is 1.5:1 to 3:1.

4. The ablation catheter according to claim 1, wherein at least a portion of outwardfacing unit normal vectors to the one or more curved surface portions include non-zero vector components parallel to the central longitudinal axis.

5. The ablation catheter according to claim 1, wherein at least one of the one or more curved surface portions has an average radius of curvature of at least 0.25 mm.

6. The ablation catheter according to claim 5, wherein the average radius of curvature is at least 0.35 mm.

7. The ablation catheter according to claim 6, wherein the average radius of curvature is at least 0.5 mm.

8. The ablation catheter according to claim 1, wherein at least one of the one or more curved surface portions includes at least one curved-surface sub-portion having a radius of curvature of at least 0.25 mm.

9. The ablation catheter according to claim 8, wherein the radius of curvature is at least 0.35 mm.

10. The ablation catheter according to claim 9, wherein the radius of curvature is at least 0.5 mm.

11. The ablation catheter according to claim 5, wherein the one or more curved surface portions include a plurality of curved surface portions, and wherein the plurality of curved surface portions have respective average radii of curvature, each of which is at least 0.25 mm.

12. The ablation catheter according to claim 1, wherein at least one of the one or more curved surface portions has an average radius of curvature equal to at least 20% of a radius of the distal electrode-support portion.

13. The ablation catheter according to claim 12, wherein the average radius of curvature equals at least 30% of the radius of the distal electrode-support portion.

14. The ablation catheter according to claim 1, wherein at least 90% of a surface area of an entirety of a surface of the electrode is curved.

15. The ablation catheter according to claim 14, wherein at least 95% of the surface area the entirety of the surface of electrode is curved.

16. The ablation catheter according to claim 1,wherein a surface of the electrode includes:at one of the following surface portions least: a first surface portion that faces entirely radially outward and a second surface portion that faces entirely radially inwardly, andremaining surface portions of the electrode other than the first and the second surface portions, andwherein at least 90% of a surface area of the remaining surface portions is curved.

17. The ablation catheter according to claim 16, wherein at least 95% of the surface area of the remaining surface portions is curved.

18. The ablation catheter according to claim 1, wherein the uninsulated electrode surface is annular.

19. The ablation catheter according to claim 1, wherein the uninsulated electrode surface is not annular.

20. The ablation catheter according to claim 1, wherein the uninsulated electrode surface circumscribes 10 - 270 degrees of the central longitudinal axis.

21. The ablation catheter according to claim 20, wherein the uninsulated electrode surface circumscribes 10 - 180 degrees of the central longitudinal axis.

22. The ablation catheter according to claim 21, wherein the uninsulated electrode surface circumscribes 10 - 90 degrees of the central longitudinal axis.

23. The ablation catheter according to claim 1, wherein the electrode circumscribes 10 - 270 degrees of the central longitudinal axis.

24. The ablation catheter according to claim 23, wherein the electrode circumscribes 10 - 180 degrees of the central longitudinal axis.

25. The ablation catheter according to claim 24, wherein the electrode circumscribes 10 - 90 degrees of the central longitudinal axis.

26. The ablation catheter according to claim 1, wherein an outermost perimeter of the electrode is elliptical.

27. The ablation catheter according to claim 26, wherein the outermost perimeter of the electrode is circular.

28. The ablation catheter according to claim 1, wherein an outermost perimeter of the electrode is shaped as a rounded rectangle.

29. The ablation catheter according to claim 28, wherein the rounded rectangle is a rounded square.

30. The ablation catheter according to claim 28, wherein the rounded rectangle is a squircle.

31. The ablation catheter according to claim 1, wherein an outermost perimeter of the electrode is shaped as a superellipse.

32. The ablation catheter according to claim 1, wherein the uninsulated electrode surface is convex as viewed from outside the distal electrode-support portion.

33. The ablation catheter according to claim 1, wherein the uninsulated electrode surface includes a planar portion.

34. The ablation catheter according to claim 33, wherein an entirety of the uninsulated electrode surface is planar.

35. The ablation catheter according to claim 1, wherein the insulated electrode surface defines a surface that faces radially inward and is concave as viewed from the central longitudinal axis.

36. The ablation catheter according to claim 1, wherein the insulated electrode surface defines a surface that faces radially inward and includes a planar portion.

37. The ablation catheter according to any one of claims 1-36, wherein at least a portion of outward-facing unit normal vectors to the one or more curved surface portions, at respective points on the one or more curved surface portions, include non-zero vector components that are (i) in a plane perpendicular to the central longitudinal axis and (ii) perpendicular to respective lines that are (a) perpendicular to the central longitudinal axis and (b) intersect the central longitudinal axis and the respective points.

38. The ablation catheter according to any one of claims 1-36, wherein at least a portion of outward-facing unit normal vectors to the one or more curved surface portions, at respective points on the one or more curved surface portions, include both:non-zero vector components parallel to the central longitudinal axis, and non-zero vector components that are (i) in a plane perpendicular to the central longitudinal axis and (ii) perpendicular to respective lines that are (a) perpendicular to the central longitudinal axis and (b) intersect the central longitudinal axis and the respective points.

39. The ablation catheter according to any one of claims 1-36,wherein at least a first portion of outward-facing unit normal vectors to the one or more curved surface portions, at respective points on the one or more curved surface portions, include non-zero vector components parallel to the central longitudinal axis, wherein at least a second portion of outward-facing unit normal vectors to the one or more curved surface portions, at respective points on the one or more curved surface portions, include non-zero vector components that are (i) in a plane perpendicular to the central longitudinal axis and (ii) perpendicular to respective lines that are (a) perpendicular to the central longitudinal axis and (b) intersect the central longitudinal axis and the respective points,wherein the first portion of the outward-facing unit normal vectors includes at least some points on the one or more curved surface portions that are not included in the second portion of the outward-facing unit normal vectors, andwherein the second portion of the outward-facing unit normal vectors includes at least some points on the one or more curved surface portions that are not included in the first portion of the outward-facing unit normal vectors.

40. The ablation catheter according to claim 39, wherein the first and the second portions include some of the same points on the one or more curved surface portions.

41. The ablation catheter according to any one of claim 1 -40, wherein the shaft is tubular and is shaped to define one or more lumens.

42. An ablation system comprising the ablation catheter according to any one of claims 1-41, the ablation system further comprising an energy source.

43. The ablation system according to claim 42, wherein the energy source is configured to apply pulsed field ablation energy.

44. The ablation system according to claim 42, wherein the energy source is configured to apply radiofrequency (RF) ablation energy.

45. A method comprising ablating tissue using the ablation catheter according to any one of claims 1-44.

46. An ablation catheter for treating atrial arrhythmia, comprising:an elongate proximal shaft; anda distal electrode-support portion, which comprises:an elongate distal shaft that includes a first shaft portion, a second shaft portion, and a shaft connecting end portion that connects a distal end of the first shaft portion to a proximal end of the second shaft portion; andone or more ablation electrodes, which are configured to ablate an atrial wall of a heart, and which are at least partially disposed along the second shaft portion, wherein, when the distal electrode-support portion is unconstrained:the first and the second shaft portions are entirely straight and the shaft connecting end portion is entirely curved,the second shaft portion defines a distal end,a central longitudinal axis of the first shaft portion is parallel to, or defines an angle of less than 10 degrees with, a central longitudinal axis of the second shaft portion,the second shaft portion is longer than the first shaft portion, and the first shaft portion runs alongside only an axial portion of the second shaft portion, and the ablation catheter defines a catheter curved portion that connects a proximal end of the first shaft portion to a distal end of the elongate proximal shaft.

47. The ablation catheter according to claim 46, wherein, when the distal electrodesupport portion is unconstrained:(a) a best-fit plane defined by the first and the second shaft portions forms a planeaxis angle with (b) a proximal-shaft central longitudinal axis of the elongate proximal shaft that passes through the distal end of the elongate proximal shaft, wherein the plane-axis angle is 45 - 135 degrees.

48. The ablation catheter according to claim 47, wherein the plane-axis angle is 60 -120 degrees.

49. The ablation catheter according to claim 48, wherein the plane-axis angle is 75 -105 degrees.

50. The ablation catheter according to claim 49, wherein the plane-axis angle is 90 degrees.

51. The ablation catheter according to claim 46, wherein, when the distal electrodesupport portion is unconstrained:the elongate proximal shaft defines a proximal-shaft central longitudinal axis thatpasses through the distal end of the elongate proximal shaft,the first and the second shaft portions define a best-fit plane, andthe proximal-shaft central longitudinal axis lies in the best-fit plane or defines a plane-axis angle with the best-fit plane, the plane-axis angle greater than 150 degrees.

52. The ablation catheter according to claim 51, wherein, when the distal electrodesupport portion is unconstrained, the proximal-shaft central longitudinal axis lies in the best-fit plane.

53. The ablation catheter according to claim 51, wherein, when the distal electrodesupport portion is unconstrained, the proximal -shaft central longitudinal axis defines the plane-axis angle with the best-fit plane, the plane-axis angle greater than 165 degrees.

54. The ablation catheter according to claim 51, wherein when the distal electrodesupport portion is unconstrained, (a) the central longitudinal axis of the first shaft portion intersects and forms an axis-axis angle with (b) the proximal-shaft central longitudinal axis, wherein the axis-axis-angle is 45 - 135 degrees.

55. The ablation catheter according to claim 54, wherein the axis-axis angle is 60 - 120 degrees.

56. The ablation catheter according to claim 55, wherein the axis-axis angle is 75 - 105 degrees.

57. The ablation catheter according to claim 56, wherein the axis-axis angle is 90 degrees.

58. The ablation catheter according to claim 46, wherein the one or more ablation electrodes comprise two or more ablation electrodes disposed along the second shaft portion.

59. The ablation catheter according to claim 46, wherein, when the distal electrodesupport portion is unconstrained, the shaft connecting end portion has a radius of curvature of 0.25 cm - 3 cm.

60. The ablation catheter according to claim 59, wherein the radius of curvature is 0.25 cm - 1 cm.

61. The ablation catheter according to claim 46, wherein, when the distal electrodesupport portion is unconstrained, the elongate distal shaft has greatest major and minordimensions perpendicular to each other, measured in a best-fit plane defined by the first and the second shaft portions, and wherein the greatest major dimension equals at least 3 times the greatest minor dimension.

62. The ablation catheter according to claim 61, wherein the greatest major dimension is at least 4 times the greatest minor dimension.

63. The ablation catheter according to claim 46, wherein the first and the second shaft portions are coplanar when the distal electrode-support portion is unconstrained.

64. The ablation catheter according to claim 46, wherein the central longitudinal axis of the first shaft portion is parallel to, or defines an angle of less than 10 degrees with, the central longitudinal axis of the second shaft portion,65. The ablation catheter according to claim 64, wherein the central longitudinal axis of the first shaft portion is parallel to the central longitudinal axis of the second shaft portion, when the distal ablation probe is unconstrained.

66. The ablation catheter according to claim 46, wherein the first shaft portion has a length of 1 - 3 cm when the distal electrode-support portion is unconstrained.

67. The ablation catheter according to claim 66, wherein the second shaft portion has a length of 2 - 6 cm when the distal electrode-support portion is unconstrained.

68. The ablation catheter according to claim 46, wherein the second shaft portion has a length of 2 - 6 cm when the distal electrode-support portion is unconstrained.

69. The ablation catheter according to claim 46, wherein, when distal electrode-support portion is unconstrained, the first shaft portion has a length that equals 1 - 3 times a closest distance between the first and the second shaft portions.

70. The ablation catheter according to claim 46, wherein a closest distance between the first and the second shaft portions is 5 - 30 mm when the distal electrode-support portion is unconstrained.

71. The ablation catheter according to any one of claims 46-70, wherein, when the distal electrode-support portion is unconstrained, the distal end of the second shaft portion is separate from the first shaft portion.

72. The ablation catheter according to claim 71, wherein, when the distal electrodesupport portion is unconstrained, the distal end of the second shaft portion is greater than 2cm from the first shaft portion.

73. The ablation catheter according to claim 71, wherein, when the distal electrodesupport portion is unconstrained, the distal end is free.

74. The ablation catheter according to any one of claims 46-70, wherein when the distal electrode-support portion is unconstrained, (a) the central longitudinal axis of the first shaft portion intersects and forms an axis-axis angle with (b) a proximal-shaft central longitudinal axis of the elongate proximal shaft that passes through the distal end of the elongate proximal shaft, wherein the axis-axis-angle is 45 - 135 degrees.

75. The ablation catheter according to claim 74, wherein the axis-axis angle is 60 - 120 degrees.

76. The ablation catheter according to claim 75, wherein the axis-axis angle is 75 - 105 degrees.

77. The ablation catheter according to claim 76, wherein the axis-axis angle is 90 degrees.

78. The ablation catheter according to any one of claims 46-70, wherein the one or more ablation electrodes are disposed entirely along the second shaft portion.

79. The ablation catheter according to any one of claims 46-70, wherein an entirety of the first shaft portion runs alongside the axial portion of the second shaft portion, when the distal electrode-support portion is unconstrained.

80. The ablation catheter according to any one of claims 46-70, wherein, when the distal electrode-support portion is unconstrained, a length of the second shaft portion is at least 1.5 times a length of the first shaft portion.

81. The ablation catheter according to claim 80, wherein, when the distal electrodesupport portion is unconstrained, the length of the second shaft portion is no more than 3 times the length of the first shaft portion.

82. The ablation catheter according to any one of claims 46-70, wherein a difference between a length of the first shaft portion and a length of the second shaft portion is 1 - 3 cm when the distal electrode-support portion is unconstrained.

83. The ablation catheter according to any one of claims 46-70, wherein the distal electrode-support portion comprises a shape memory material that causes the elongate distalshaft to define the first and the second straight shaft portions running alongside each other and the entirely curved shaft connecting end portion, when the elongate distal shaft is unconstrained.

84. An ablation system comprising the ablation catheter according to any one of claims 46-83, the ablation system further comprising an intravascular delivery sheath, in which the ablation catheter is removably disposed for delivery such that the elongate distal shaft is constrained by the intravascular delivery sheath, such that the first and the second shaft portions are disposed at respective, non-longitudinally-overlapping locations along the intravascular delivery sheath.

85. An ablation system comprising the ablation catheter according to claim 46, the ablation system further comprising an energy source.

86. The ablation system according to claim 85, wherein the energy source is configured to apply pulsed field ablation energy.

87. The ablation system according to claim 85, wherein the energy source is configured to apply radiofrequency (RF) ablation energy.

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