Systems and methods for an ablation catheter for intramyocardial ablation

Abstract

A catheter system for performing intramyocardial ablation is provided. In one example, a microcatheter includes a flexible catheter tube and a conductive ablation electrode coupled to the catheter tube near a distal tip of the catheter tube, the ablation electrode including one or more openings to facilitate delivery of fluid out of the ablation electrode.

Description

Attorney Docket No. NIH24304PCTSYSTEMS AND METHODS FOR AN ABLATION CATHETER FOR INTRAMYOCARDIAL ABLATIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Provisional Application No. 63 / 716.145, filed November 4, 2024, and entitled “SYSTEMS AND METHODS FOR AN ABLATION CATHETER FOR INTRAMYOCARDIAL ABLATION,” the entire contents of which is hereby incorporated by reference for all purposes.FIELD

[0002] The present description relates generally to an apparatus for deep myocardial ablation, and more specifically to an ablation catheter for deep myocardial ablation.BACKGROUND / SUMMARY

[0003] Ventricular tachycardia (VT) is a form of heart arrhythmia originating in the ventricles of the heart. Arrhythmias can originate from scar tissue or damage in the ventricular myocardium or from areas of increased automaticity. In some cases, VT can be treated by performing ablation on scarred or damaged tissue within the ventricles to interrupt the electrical signals causing VT. Typically, ablation is carried out on endocardial and / or epicardial surfaces. However, arrhythmia sources in the left ventricular (LV) summit, inter-ventricular septum, papillary muscles, and other LV intramyocardial sites have been difficult to access from the endocardial and epicardial surfaces for ablation. Consequently, high recurrence rates in VT are associated with inadequate or failed ablation at these sites.

[0004] In one example, the issues described above may be addressed by a microcatheter for intramyocardial navigation and ablation, the microcatheter including a flexible catheter tube and a conductive ablation electrode positioned near a distal tip of the catheter tube, the ablation electrode including one or more openings to facilitate delivery of fluid out of the ablation electrode.

[0005] It should be understood that the brief description above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimedAttorney Docket No. NIH24304PCT subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The present disclosure will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below:

[0007] FIG. 1 depicts an example catheter system;

[0008] FIG. 2 depicts a first view of an ablation catheter of the catheter system of FIG. 1;

[0009] FIG. 3 depicts the ablation catheter of FIG. 2 coaxially arranged with a navigation guide wire;

[0010] FIG. 4 depicts a hub end of the ablation catheter and navigation guidewire of FIG. 3;

[0011] FIG. 5 depicts a second view of the ablation catheter of the catheter system of FIG. 1 ;

[0012] FIGS. 6 and 7 depict views of electrodes having coupling extensions that may be incorporated into the ablation catheter of the catheter system of FIG. 1;

[0013] FIG. 8 shows the ablation catheter of the catheter system of FIG. 1 without incorporation of the electrodes;

[0014] FIG. 9 shows the ablation catheter of the catheter system of FIG. 1 with incorporation of the electrodes;

[0015] FIG. 10 schematically shows a process for navigation and ablation using a catheter system as disclosed herein;

[0016] FIG. 11 is a flow chart illustrating a method for performing an ablation procedure with a catheter system as disclosed herein;

[0017] FIG. 12 schematically shows an example kit including aspects of the catheter system as disclosed herein;

[0018] FIG. 13 depicts a third view of the ablation catheter of the catheter system of FIG. 1;

[0019] FIG. 14 depicts a fourth view of the ablation catheter of the catheter system of FIG. 1;

[0020] FIG. 15 shows cross-sectional view of the ablation electrode of FIG. 2;

[0021] FIGS. 16 and 17 show cross-sectional views of various ablation electrode configurations;

[0022] FIG. 18 depicts a fifth view of the ablation catheter of the catheter system of FIG. 1;Attorney Docket No. NIH24304PCT

[0023] FIG. 19 depicts a sixth view of the ablation catheter of the catheter system of FIG. 1; and

[0024] FIG. 20 depicts a seventh view of the ablation catheter of the catheter system of FIG. 1.DETAILED DESCRIPTION

[0025] The following description relates to a system of an electrically insulated electrodeguidewire and an ablation microcatheter and the method by which this system can be used to treat ventricular tachycardia (VT). This system may hereafter be referred to as VINTAGE (Ventricular Intramyocardial Navigation for Tachycardia Ablation Guided by Electrograms). VT can originate from damaged or scarred tissue or areas of increased automaticity located within the ventricles of the heart that disrupt electrical function necessary for normal heart function. For example, regions of scar and slow conduction can form the substrate for reentrant conduction pathways underlying VT. Ablation of key scarred or damaged tissue targets with radio-frequency (RF) energy may block the transmission of pathological electrical signals thereby treating VT. Current systems of ablation have their own limitations. For example, endocardial monopolar ablation may have difficulty reaching deep targets whereas epicardial monopolar ablation is hindered by the presence of thick epicardial fat and the threat of injury to nearby coronary arteries.

[0026] Thus, the VINTAGE system disclosed herein addresses these issues via guidewire navigation to intramyocardial targets and ablation in the myocardium with a fenestrated or otherwise segmented ablation electrode. The ablation electrode may include one or more openings to facilitate irrigation during ablation. The one or more openings may be static (e.g., fixed in size and position) or dynamic (e.g., the size of each opening may be adjustable and / or the one or openings may be exposed upon actuation of a particular component) and may be of any suitable shape, including but not limited to circular, semi-circular, oval, rectangular, spiral, helical, sinusoidal, clamshell, and the like. As shown in FIGS. 1-4, the VINTAGE system may include an ablation microcatheter including a polymer tube and a fenestrated, conductive ablation electrode coupled to the polymer tube near a distal tip of the polymer tube. The ablation microcatheter (e.g., polymer tube) is configured for coaxial arrangement with a navigation guidewire and has an inner lumen with a greater cross-sectional diameter than a cross-sectional diameter of the navigation guidewire. The size mismatch between the inner lumen of the ablation microcatheter and theAttorney Docket No. NIH24304PCT navigation guidewire may facilitate irrigation from openings (e.g., fenestrations) of the ablation electrode, via irrigant in the inner lumen, during ablation. As shown in FIGS. 13 and 14, the ablation electrode may be segmented to include or expose openings for irrigation. For example, the ablation electrode may include one or more tines that may be configured to move outward from the ablation electrode to expose strip-like openings in the ablation electrode, as shown in FIG. 13, or the ablation electrode may be comprised of electrode strips configured to bend / flex so as to form clamshell-like openings in the ablation electrode, as shown in FIG. 14. Further, as depicted in FIG. 18, the electrode strips may be wound partially around a central axis of the ablation electrode in a helical-like fashion such that when the strips bend / flex, helical openings are formed. In still further examples, the ablation electrode may be comprised of a continuous segment of material that is wound around the central axis of the ablation electrode to form a single helical opening that spans the length of the ablation electrode, as shown in FIGS. 19 and 20. The ablation electrode may be coupled to the polymer tube in an end-to-end fashion, such that the polymer tube does not extend in the region where the ablation electrode is located, as shown in FIG. 15. In other examples, as shown in FIGS. 16 and 17, the polymer tube may extend along an inner surface of the ablation electrode.

[0027] In some examples, the ablation microcatheter further includes one or more mapping electrodes configured to facilitate tracking by electroanatomic navigation (also known as electroanatomic mapping), focal electrogram sensing, and / or focal myocardial pacing. The one or more mapping electrodes may include a first mapping electrode positioned at a distal end of the ablation microcatheter (e.g., between the ablation electrode and the distal tip of the polymer tube). In some examples, the one or more mapping electrodes may include a second mapping electrode positioned proximal the first mapping electrode, such as on an opposite side (e.g., proximal) of the ablation electrode. For example, as shown in FIGS. 1-3, the first mapping electrode may be positioned closer to the ablation electrode, or the first mapping electrode may be positioned further from the ablation electrode (and closer to the distal tip of the ablation microcatheter), as shown in FIG. 5. In some examples, to facilitate reduction in electrode detachment from the ablation microcatheter, the one or more mapping electrodes and / or the ablation electrode may include helical, feathered, dentate, and / or tapered extensions, as shown in FIGS. 6 and 7, that may be incorporated into the polymer tube of the ablation microcatheter, as shown in FIGS. 8 and 9.Attorney Docket No. NIH24304PCT

[0028] As shown in FIGS. 10 and 11, at least the ablation microcatheter and the navigation guidewire may be used to traverse the myocardium to reach an ablation target, guided by electrograms detected from the electrodes on the ablation microcatheter and guidewire, or by position information (such as spatial and / or geometric position informationO encoded on electromagnetic fields generated by electroanatomic mapping systems. Irrigation with an electrolyte may be performed via the flush port and fenestrations / openings of the ablation microcatheter and ablation performed with the ablation electrode, to alter the electrical and / or physicochemical characteristics of the target myocardial substrate. Aspects of the VINTAGE system, including the ablation microcatheter and the navigation guidewire, may be packaged in a kit, as shown in FIG. 12.

[0029] Turning now to the figures, FIG. 1 depicts an example of an ablation catheter system 100 (also referred to as a VINTAGE system), in a first configuration. FIG. 1 (as well as FIGS. 2- 9 and 13-19B) includes a Cartesian coordinate system 199 to orient each view of the ablation catheter system 100 provided herein. In the example shown in FIG. 1, the y-axis may be a vertical axis (e.g., extending parallel to gravity with the positive y direction pointing in the direction of the arrow, away from ground), the x-axis of coordinate system 199 may be a longitudinal axis (e.g., horizontal axis), and / or the z-axis of coordinate system 199 may be a lateral axis, in one example. However, the axes may have other orientations, in other examples. When referencing direction, positive may refer to in the direction of the arrow of the x-axis, y-axis, and z-axis and negative may refer to in the opposite direction of the arrow of the x-axis, y-axis, and z-axis. An unfilled circle may represent an arrow and an axis facing away, or negative to, a view. However, it is to be appreciated that the ablation catheter system 100 may be held or used in any orientation without departing from the scope of this disclosure. Further, the term distal end may refer to a first end of the ablation catheter system 100 configured to be positioned within a heart of a patient and the term proximal end may refer to a second end of the ablation catheter system 100 configured to remain external to the patient. In some examples, the patient may be human, however in other examples the patient may be nonhuman.

[0030] The ablation catheter system 100 includes an ablation microcatheter 102 that includes a shaft 101 (e.g., a polymer tube) including a body 103 and a tapered nosecone 106. The ablation microcatheter 102 further includes a first mapping electrode 104 coupled to the shaft 101 at a distal end of the ablation microcatheter 102, a fenestrated (or segmented), conductive ablation electrodeAttorney Docket No. NIH24304PCT108 coupled to the shaft 101 at the distal end (e.g., proximal the first mapping electrode 104), and a second mapping electrode 109 coupled to the shaft 101 proximal the ablation electrode 108. The ablation microcatheter 102 may have a generally cylindrical shape with a hollow interior to facilitate a coaxial arrangement of a navigation guidewire 110. The shaft 101, and specifically the tapered nosecone 106, may terminate at a distal tip 105 that has an opening through which the navigation guidewire 110 may extend. At the distal tip, the ablation microcatheter 102 may have a first inner cross-sectional diameter (e.g., along the z axis) in a range of 0.014-0.018 inches. The tapered nosecone 106 may taper in width / cross- sectional area along the x axis (and specifically may taper in the negative x direction). Accordingly, at least in some examples, the ablation microcatheter 102 may have a larger cross-sectional area in the body 103 (e.g., proximal of the first mapping electrode 104) than at the distal tip 105. For example, the ablation microcatheter 102, along its entirety other than the tapered nosecone 106, may have a second inner cross- sectional diameter (e.g., along the z axis) in a range of 0.021-0.035 inches and an outer cross- sectional diameter in a range of 0.025-0.038 inches. Each of the first mapping electrode 104 and the second mapping electrode 109 may be surface ring electrodes that extend radially around an entire circumference of the shaft 101 and have inner and outer diameters that match the inner and outer diameters of the ablation microcatheter mentioned above. However, other geometrical arrangements are possible without departing from the scope of this disclosure. For example, one or both of the first mapping electrode 104 and the second mapping electrode 109 may be strips or partial rings that extend only partially around the shaft 101, such as semi-circular electrodes that extend radially around only half the circumference of the shaft 101. In the example illustrated in FIGS. 1-3, the first mapping electrode 104 may be positioned between the tapered nosecone 106 and the ablation electrode 108, though the first mapping electrode 104 may be positioned elsewhere on the ablation microcatheter 102 without departing from the scope of this disclosure. Further, in some examples, more than two mapping electrodes may be provided.

[0031] The ablation microcatheter 102 may have a suitable length (e.g., along the x axis) to facilitate placement of the ablation microcatheter 102 in a patient and specifically to facilitate placement of the distal end of the ablation microcatheter 102 in a heart of the patient while the proximal end of the ablation microcatheter 102 remains external to the patient. The ablation microcatheter 102 may include an opening at the distal tip 105 to allow insertion and removal of the navigation guidewire 110 as well as an opening at the proximal end. At the proximal end, theAttorney Docket No. NIH24304PCT ablation microcatheter 102 may include and / or be coupled to various hardware 112 to facilitate navigation of the ablation microcatheter 102 as well as fluid irrigation during an ablation procedure.

[0032] The hardware 112 may include an irrigation port 112a, electrode connectors, an RF connector, and a hemostatic valve. In some examples, the hemostatic valve may be integrated with the ablation microcatheter 102, or the hemostatic valve may be detachable and the ablation microcatheter 102 may include a connector (e.g., a Luer lock connector) to facilitate coupling of the hemostatic valve. The electrode connectors may be configured to couple to a signal processor, for example, via one or more first connections 118 (e.g., signal wires). The first mapping electrode 104 and the second mapping electrode 109 may be coupled to the electrode connectors via a suitable connection, such as wires extending along or within a wall forming the ablation microcatheter 102 (e.g., within the body 103). In some examples, the electrode connectors may include terminals of the wires that are accessible to the one or more first connections 118. In other examples, the electrode connectors may include external connector(s) configured to mate with a corresponding connection of the one or more first connections 118. Navigation of the ablation microcatheter 102 may be guided by x-ray fluoroscopy, electroanatomic mapping (EAM), and / or electrocardiographic radial depth navigation (EDEN), and / or intracardiac ultrasound. EDEN provides real-time, depth- specific unipolar intramyocardial electrogram patterns that indicate intramural radial position during microcatheter and guidewire navigation based on output from the first mapping electrode 104, the second mapping electrode 109, and / or an exposed conductor of the navigation guidewire, explained below. The RF connector may facilitate coupling to an RF generator 208, explained below.

[0033] Thus, the ablation microcatheter 102 includes one or more mapping electrodes allowing intramyocardial EAM and / or EDEN tracking and a fenestrated / segmented ablation electrode to allow RF ablation and irrigation during RF ablation. The ablation microcatheter 102 is capable of tracking over the navigation guidewire 110, is capable of intramyocardial pacing, is capable of deep intramyocardial positioning under x-ray, EAM, and EDEN guidance, is capable of RF ablation, and is capable of infusing electrolyte around the ablation electrode. The ablation microcatheter 102 includes electrode connectors for EAM and a connector for an RF generator for ablation. The ablation microcatheter 102 may be electrically insulated from the navigation guidewire and any surrounding catheters and media. The ablation microcatheter 102 may have aAttorney Docket No. NIH24304PCT"short" rotating hemostatic valve / adaptor (e.g., of less than 2cm) and allows coaxial placement of the navigation guidewire 110 as well as a sidearm (e.g., the irrigation port 112a) to allow electrolyte infusion. The ablation microcatheter 102 may have a length of 135-175 cm.

[0034] The navigation guidewire 110 may comprise a thin (e.g., having an outer diameter in a range from 0.01 inches to 0.02 inches) cylindrical material having a stiffness (or flexibility) that enables insertion into and navigation within the myocardium. For example, the navigation guidewire 110 may comprise stainless steel and / or nickel-titanium alloy (e.g., Nitinol) and / or another suitable biocompatible alloy, and may be a braided or coiled wire for increased pushability and kink resistance. Further, a length of the navigation guidewire 110 is electrically insulated except for an exposed conductor 111 at the distal end of the navigation guidewire 110 and a connection point at the proximal end of the navigation guide wire 110. For example, the navigation guidewire 110 may be coated with one or more insulators except for the exposed conductor 1 11 and the connection point that electrically couples the exposed conductor to an electrode connector 116 via the electrically conductive transmission line. In this way, the navigation guidewire 110 may include an insulated region and an uninsulated region (e.g., the exposed conductor 111). The electrode of the navigation guidewire (e.g., the exposed conductor 111) may be a unipolar electrode in some examples. The electrode connector 116 may be coupled to the signal processor, for example, via a second connection 122 (e.g., a signal wire). The electrode connector 116 may be configured to limit the mechanical limitation on the operator torqueing the navigation guidewire during operation / advancement / retraction, to ensure tactile feedback and to minimize physical constraints on torque / advancement / withdrawal. The navigation guidewire 110 may have a tip stiffness (measured by lateral deflection at a fixed distance from the tip, such as 10mm) at the distal end of the navigation guidewire 110 ranging from 6 to 60 g, such as 20-40 g, allowing a short l-2mm x 30° "CTO" curve, as well as a straight tip (e.g., at the proximal end), each with electrical insulation to allow EDEN and EAM tracking. The navigation guidewire 110 may include radiopaque markers allowing fluoroscopic tracking. The distal tip of the navigation guidewire 110 has an insulation-free segment ~ 1mm in length, for EAM / EDEN; the proximal tip of the navigation guidewire 110 has an insulation-free segment ~10mm in length, for attachment to an electrode connector 116 to allow EAM / EDEN. The length of the navigation guidewire 110 may be 200- 300cm, in some examples. In some examples, the electrode connector 116 may be detachable.Attorney Docket No. NIH24304PCT

[0035] Thus, the ablation catheter system 100 in the first configuration includes a coaxial arrangement of the ablation microcatheter 102 and the navigation guidewire 110, with the navigation guide wire 110 accommodated within the ablation microcatheter 102. During an ablation procedure, the ablation catheter system 100 may be navigated to the heart (e.g., via a guiding sheath and / or catheter in some examples) and advanced into the myocardium, to any target within the wall of the left ventricle, for example. Navigation of the ablation catheter system 100 may be guided by x-ray fluoroscopy, EAM, EDEN, and / or intracardiac echocardiography (ICE). Additional details about navigating the ablation catheter system 100 are provided below.

[0036] Once the ablation microcatheter 102 reaches the target, ablation of the target may be performed via the ablation electrode 108. The relatively large diameter of the ablation microcatheter 102 (and the irrigation port 112a) relative to the relatively small diameter of the navigation guidewire 110, as well as the fenestrations / openings of the ablation electrode 108, may facilitate irrigation of the target with an electrolyte prior to and during ablation. The irrigation may be facilitated by an irrigation pump 206 fluidly coupled to the irrigation port 112a. When the irrigation pump 206 is coupled to the irrigation port 112a and the irrigation pump 206 is activated, the electrolyte may be pumped through the interior of the ablation microcatheter 102 and out of the fenestrations of the ablation electrode 108. The irrigation pump 206 may be capable of infusing intramyocardial ionic irrigant (such as 0.9% (normal) or 0.45% (half-normal) saline solution). In some examples, the irrigation pump 206 may include timing and gating circuitry to automate initiation of infusion / infiltration / irrigation approximately 1 minute before initiation of RF ablation, and continuing at approximately the same rate for the duration of the RF ablation. The irrigant may also be a caustic agent intended to effect adjunctive chemoablation, using agents such as alcohols or short-chain carboxylic acid such as acetic acid.

[0037] Ablation may be achieved via the RF generator 208 coupled to the ablation microcatheter 102, which may be activated to deliver RF energy to the target via the ablation electrode 108. The RF generator 208 may be capable of generating kilohertz AC radiofrequency waves ranging 10-100 W intended to achieve permanent thermal tissue injury. The RF generator 208 may include real-time impedance monitoring, a dispersive electrode, and attendant safety circuitry. In other examples, the RF generator 208 may include microsecond or nanosecond RF pulse trains intended to achieve non-thermal permanent tissue injury, sometimes described as "pulsed field ablation." Some examples may allow automatic modulation and cessation of energyAttorney Docket No. NIH24304PCT based on pre-specified changes in impedance. Further, in some examples, rather than delivering RF energy, the RF generator 208 may instead be configured to deliver microwaves. As such, ablation may be achieved with RF, pulsed-field, or microwave energy via the ablation electrode.

[0038] FIG. 2 shows a magnified view of the distal end of the ablation microcatheter 102 in a second configuration (e.g., without coaxial arrangement with the navigation guidewire), showing the distal tip 105. tapered nosecone 106, first mapping electrode 104, ablation electrode 108, second mapping electrode 109, and body 103. The first mapping electrode 104 may have a length along the x axis of 1-2 mm. The first mapping electrode 104 may be separated from the tapered nosecone 106 by a first insulating segment 202 (e.g., a first section of the polymer tube) and from the ablation electrode 108 by a second insulating segment 204 (e.g., a second section of the polymer tube). The ablation electrode 108 may be comprised of a hollow, circular segment of metal that has a length along the x axis of 10- 15 mm. The ablation electrode 108 include a plurality of fenestrations (e.g., apertures), such as first fenestration 128, that extend through the metal of the ablation electrode. The number, size, shape, and placement of the fenestrations may be nonlimiting and may be selected based on a desired irrigation rate, position of the target, and other considerations. FIG. 2 shows a first example configuration of the ablation electrode that includes a plurality of circular, evenly spaced fenestrations. Other example configurations of the ablation electrode are shown in FIGS. 13, 14, and 18-20 and described below.

[0039] As shown in FIG. 2, the fenestrations may be circular and of equal diameter (e.g., 0.5- 1 mm). The fenestrations may be arranged around the ablation electrode 108 in an even, repeating pattern. For example, the fenestrations may be arranged into a plurality of rows that extend longitudinally (e.g., along the x axis). Each row may include the same number of longitudinally- aligned, evenly-spaced fenestrations (e.g., six). The rows may be axially offset from each other in an alternating pattern. For example, a first row may be axially offset relative to a second row, such that a first fenestration of the first row (e.g.. the first fenestration 128) is closer to a distal edge of the ablation electrode 108 than a first fenestration of the second row (e.g., second fenestration 129). As such, the fenestrations are distributed into a plurality of radial groups that are longitudinally offset in an alternating pattern. For example, the first fenestration 128 may be included in a first radial group of circumferentially- aligned fenestrations that are evenly spaced around the circumference of the ablation electrode 108. The second fenestration 129 may be included in a second radial group of circumferentially-aligned fenestrations that are evenly spacedAttorney Docket No. NIH24304PCT around the circumference of the ablation electrode 108. Due to the offset pattern of the rows of fenestrations, the first fenestration 128 is not longitudinally- aligned with any fenestrations in the second radial group, but is instead longitudinally-aligned with a fenestration in a third radial group, a fifth radial group, etc. As such, the ablation electrode 108 may include a portion of metal between each pair of adjacent, longitudinally- aligned fenestrations and between each pair of adjacent, circumferentially-aligned fenestrations, such that the metal portions form a body that is electrically continuous around the fenestrations. The fenestrations may be distanced from each terminal edge of the ablation electrode by a suitable amount, such as 0.5-1 mm.

[0040] However, other configurations are possible, such as non-circular (e.g., rectangular) fenestrations, fenestrations of varying diameter and / or shape, and / or an uneven pattern of fenestrations. For example, the fenestrations may be distributed such that more fenestrations (or all of the fenestrations) are located on one side of the ablation electrode 108 to facilitate directed, asymmetrical irrigation. In some examples, the body 103 may include longitudinal grooves inside the inner lumen (e.g., on an inner surface of the body 103 / polymer tube) to enhance irrigation fluid delivery.

[0041] The second mapping electrode 109 may have the same length as the first mapping electrode 104 (e.g., a length along the x axis of 1-2 mm). The second mapping electrode 109 may be separated from the ablation electrode 108 by a third insulating segment 205 (e.g., a third section of the polymer tube). The tapered nosecone 106, first insulating segment 202, the second insulating segment 204, the third insulating segment 205, and the body 103 may collectively form the shaft 101 (e.g., the polymer tube).

[0042] The first insulating segment 202, the first mapping electrode 104, the second insulating segment 204, the ablation electrode 108, the third insulating segment 205, the second mapping electrode 109, and the body 103 may all be circular and hollow with the same or substantially similar (e.g., within 5-10%) inner diameter, to thereby create an inner lumen that extends from the proximal / hub end of the body 103 (shown in FIG. 4 and described in more detail below) to the tapered nosecone 106. Further, the tapered nosecone 106, the first insulating segment 202, the second insulating segment 204, the third insulating segment 205, and the body 103 may be comprised of the same material (e.g., polymer), at least in some examples. Likewise, the first mapping electrode 104, the ablation electrode 108, and the second mapping electrode 109 may allAttorney Docket No. NIH24304PCT be comprised of the same material, such as platinum-iridium alloy, stainless steel alloy, titanium, gold-plate, etc. In some examples, molybdenum-rhenium may be used to allow a lower profile.

[0043] FIG. 3 shows another magnified view of the distal end of the ablation microcatheter 102, in the first configuration where the ablation microcatheter is coaxially arranged with the navigation guidewire 110. The navigation guidewire 110 can be seen within the inner lumen of the ablation microcatheter 102 via the fenestrations of the ablation electrode 108. The size mismatch between the navigation guidewire 110 (e.g., diameter of 0.1-0.2 inches, such as 0.014 inches) and central lumen (e.g., diameter of 0.021-0.035 inches) may allow irrigant to be accommodated in the central lumen and be expelled out of the fenestrations of the ablation electrode 108 during ablation. The navigation guidewire 110 may extend out of the distal tip 105. Due to the tapering of the tapered nosecone 106. the size mismatch between the navigation guidewire 110 and the distal tip 105 may be relatively small, which may allow the ablation microcatheter 102 to slide over the navigation guidewire 110 but prevent flow of irrigant out of the distal tip 105. Thus, the tapered nosecone 106 tapers in cross-sectional diameter near and at the distal tip 105, such that a cross- sectional diameter of the nosecone 106 at the distal tip substantially matches the cross-sectional diameter of the navigation guidewire 110 (e.g., the cross-sectional diameter of the distal tip 105 may be the same as the cross-sectional diameter of the navigation guidewire 110, or the cross- sectional diameter of the distal tip 105 may be slightly larger, such as 1-5% larger, than the cross- sectional diameter of the navigation guidewire 110). In this way, when the navigation guidewire 110 is accommodated in the ablation microcatheter 102 and extends outward from the distal tip 105, fluid delivery from the distal tip 105 is blocked.

[0044] FIG. 4 schematically shows the proximal / hub end of the ablation microcatheter 102 and navigation guidewire 110. The ablation microcatheter 102 may terminate at a hub, which may include or be the hardware 112 of FIG. 1. The hardware 112 may facilitate coupling between elements of the ablation microcatheter 102 and electrode connectors and an RF connector, as explained above with respect to FIG. 1. In FIG. 4, the hardware 112 is coupled to an RF connector 402, a positive electrode connector 404, and a negative electrode connector 406. It is to be appreciated that the ablation electrode 108 may be electrically coupled to the RF connector 402, and each of the first mapping electrode 104 and second mapping electrode 109 may be separately connected to each of the positive electrode connector 404 and negative electrode connector 406. The hub of the ablation microcatheter 102 may include an opening through which the navigationAttorney Docket No. NIH24304PCT guidewire 110 extends. While not shown, the hardware 112 may further include a port for connecting to an irrigation pump, as explained above.

[0045] FIG. 5 shows another magnified view of the distal end of the ablation microcatheter 102 in the second configuration, showing the distal tip 105, tapered nosecone 106, first mapping electrode 104, ablation electrode 108, second mapping electrode 109, and body 103. The ablation microcatheter 102 shown in FIG. 5 is similar to the ablation microcatheter shown in FIG. 2. However, the first mapping electrode 104 of the ablation microcatheter 102 of FIG. 5 is positioned on the tapered nosecone 106. Thus, the first mapping electrode 104 in FIG. 5 likewise tapers and may be spaced apart from the ablation electrode 108 by a larger amount than the first mapping electrode 104 in FIG. 2.

[0046] The electrodes of the ablation microcatheter 102 shown in FIGS. 2, 3, and 5 may be ring electrodes with straight / flat edges that may be mounted on the ablation microcatheter 102 by bonding the edges of the electrodes to the material of the nosecone, first insulating segment, second insulating segment, and / or body using glue, heat, and / or other mechanisms, such as embedding the electrodes in the shaft by reflowing or extruding the shaft material segments before and after the mapping electrodes. However, the straight edges of the electrodes may not adhere to the elements of the ablation microcatheter as reliably as desired for all applications and may be prone to dislodging. Thus, one or more of the electrodes may include extensions at the edges that allow enhanced bonding to the polymer components of the ablation microcatheter (e.g., the nosecone, first insulating segment, second insulating segment, and / or body) and providing smoother mechanical transition from the polymer catheter shaft to the metal electrode body. The extensions may be helical, feathered, dentate, and / or tapered to allow embedding of the extensions in the polymer tube and increase the contact area between the electrode edges and the polymer tube. The extensions, and in particular helical configurations of the extensions, may enhance EAM tracking functionality.

[0047] FIG. 6 shows an example mapping electrode 600 with helical extensions. Mapping electrode 600 is a non-limiting example of the first mapping electrode 104 and / or the second mapping electrode 109 of FIG. 1 and may be included on the ablation microcatheter 102. The mapping electrode 600 may include a ring electrode segment 602 that comprises a hollow, circular (e.g., annular) electrode, as explained above with respect to the first mapping electrode 104, for example. The mapping electrode 600 may further include a first extension 604 and a secondAttorney Docket No. NIH24304PCT extension 606, each extending out from a respective side of the ring electrode segment 602. The first extension 604 may be a helical extension made of the same material as the ring electrode segment 602 and including a suitable number of turns (e.g.. one and a half). In some examples, the entirety of the first extension 604 may have the same inner and outer diameter as the ring electrode segment 602. In other examples, the first extension 604 may taper (e.g., narrow) in a direction away from the ring electrode segment 602. FIG. 6 may be a front-side view of the mapping electrode 600, and the first extension 604 may extend out of the ring electrode segment 602 on an opposite, back side of the mapping electrode 600. The second extension 606 may be a helical extension made of the same material as the ring electrode segment 602 and with a suitable number of turns (e.g., one and a half). In some examples, the entirety of the second extension 606 may have the same inner and outer diameter as the ring electrode segment 602. In other examples, the second extension 606 may taper (e.g., narrow) in a direction away from the ring electrode segment 602. The second extension 606 may extend out of the ring electrode segment 602 on the back side of the mapping electrode 600. The first extension 604 may extend out of the ring electrode segment 602 closer to a bottom of the mapping electrode 600 while the second extension 606 may extend out of the ring electrode segment 602 closer to a top of the mapping electrode 600. In all, the first extension 604, the ring electrode segment 602, and the second extension 606 may create a helical shape with a suitable number of turns (e.g., four), with a middle section of increased width.

[0048] FIG. 7 shows an example ablation electrode 700 with helical extensions. Ablation electrode 700 is a non-limiting example of the ablation electrode 108 of FIG. 1 and may be included on the ablation microcatheter 102. The ablation electrode 700 may include an ablation electrode segment 702 that comprises a hollow, circular (e.g.. annular) electrode with fenestrations or segmentations, as explained above with respect to the ablation electrode 108, for example. The ablation electrode 700 may further include a first extension 704 and a second extension 706, each extending out from a respective side of the ablation electrode segment 702. The first extension 704 and the second extension 706 may be similar to the first extension 604 and the second extension 606 of FIG. 6, and thus the description of the first extension 604 and the second extension 606 provided above likewise applies to the first extension 704 and the second extension 706.

[0049] FIG. 8 shows an example ablation catheter 802 with electrodes removed to allow visualization of the connecting components of the ablation catheter 802 that facilitate coupling of the electrodes to the ablation catheter 802. In the example shown in FIG. 8, the first mappingAttorney Docket No. NIH24304PCT electrode and the second mapping electrode are electrodes with coupling extensions (such as the mapping electrode 600 of FIG. 6) and thus the ablation catheter 802 includes coupling sections to facilitate enhanced bonding of the electrode extensions. The coupling sections include a first section 810 coupled to the nosecone 806 and a second section 812, wherein the first section 810 and the second section 812 are configured to couple to the first mapping electrode (not shown in FIG. 8, but shown in FIG. 9). The first section 810 is a non-limiting example of the first insulating segment 202 and the second section 812 is a non-limiting example of the second insulating segment 204. The coupling sections additionally include a third section 814 and a portion of the body 803, wherein the third section 814 and the portion of the body 803 are configured to couple to the second mapping electrode. The third section 814 is a non-limiting example of the third insulating segment 205 and the body 803 is a non-limiting example of the body 103. The second section 812 and the third section 814 are additionally configured to couple to an ablation electrode 808, which is a non-limiting example of the ablation electrode 108. In the illustrated example, the ablation electrode 808 does not include extensions.

[0050] As appreciated from FIG. 8, the first section 810, the second section 812, the third section 814, and the portion of the body 803 each include a helical gap that is shaped and sized to accommodate a respective electrode extension. FIG. 9 shows the ablation catheter 802 with electrodes coupled the ablation catheter 802. For example, a first mapping electrode 804 is coupled to the first section 810 on a first side and to the second section 812 on a second side. The first mapping electrode 804 may be a non-limiting example of the mapping electrode 600 and thus includes two extensions. The first extension of the first mapping electrode 804 may be coupled to the first section 810 and the second extension of the first mapping electrode 804 may be coupled to the second section 812. As shown, the first extension may fit into the helical gap of the first section 810 and the second extension of the first mapping electrode 804 may fit into the helical gap of the second section 812. The second mapping electrode 809 may be coupled to the third section 814 and the portion of the body 803 in a similar manner.

[0051] The inclusion of the electrode extensions may increase the surface area over which the electrodes are coupled to the connecting elements of the ablation catheter, thereby increasing the durability of the bonding. It is to be appreciated that the electrode extensions may taper / narrow in diameter in a direction away from the ring electrode component, as explained above. Further, the mapping electrodes may be coupled to the microcatheter shaft during reflowing or extruding ofAttorney Docket No. NIH24304PCT the shaft material segments distal and proximal the mapping electrodes. In doing so, the electrode surface may be aligned with the shaft surface almost perfectly for a smooth profile and the mapping electrodes may be embedded into the shaft to provide a smoother mechanical transition, preventing kinks and detachment of the electrodes, and further enhancing EAM tracking functionality. The electrode extensions may be fully or partially embedded in the shaft / polymer tube. The electrode segment of the mapping electrode may not be covered by the polymer tube and thus an outer surface of the electrode segment may be exposed to ambient. When the electrode extensions are tapered and thus narrow in cross-sectional diameter in a direction away from the electrode segment, the amount of polymer on the outside and the inside of the extensions may vary along the extensions. For example, the thickness of the polymer on the outer side of the extension may increase in a direction away from the electrode segment. Because the electrodes may be coupled to the polymer tube during formation of the polymer tube (e.g., via reflowing or extruding), the helical gaps in the polymer tube described above may not be pre-formed but may reflect areas where the electrode extensions are included on and / or within the polymer tube.

[0052] FIGS. 13 and 14 provide additional example configurations for segmented ablation electrodes. FIG. 13 shows a second ablation electrode 1302 that may be incorporated into ablation microcatheter 102. Second ablation electrode 1302 may be positioned on the ablation microcatheter 102 similarly to ablation electrode 108, and may be comprised of the same material(s), have the same length, and have the same inner diameter as the ablation electrode 108. Rather than include a plurality of fenestrations, the second ablation electrode 1302 may include a main body 1304 supporting a plurality of tines, such as a first tine 1306 and a second tine 1308. Each tine of the plurality of tines may be shaped and sized to be accommodated in a respective opening of the second ablation electrode 1302 and may be pre-tensioned or otherwise configured to move outward from the central axis of the second ablation electrode 1302 to expose the respective opening. For example, the first tine 1306 may be shaped and sized to be accommodated within a first opening 1310, and may move outward from the first opening 1310 to facilitate fluidic coupling between the inner lumen of the ablation microcatheter 102 and the surrounding environment, via the first opening 1310. Eikewise, the second tine 1308 may be shaped and sized to be accommodated within a second opening 1312, and may move outward from the second opening 1312 to facilitate fluidic coupling between the inner lumen of the ablation microcatheter 102 and the surrounding environment, via the second opening 1312. In the example shown in FIG.Attorney Docket No. NIH24304PCT13, the plurality of tines may include six tines and the second ablation electrode 1302 may include six openings. The openings may be strip-like in shape (e.g., have a length along the x axis that is larger than a radial width of the opening around the circumference of the second ablation electrode 1302), with square corners or rounded corners. The openings (and hence tines) may be arranged in two radial groups that are offset from each other (e.g., the openings in the two groups are not aligned along the x axis) so that, looking down the ablation microcatheter 102 when the tines are positioned in the outward position as shown in FIG. 13, the tines are arranged radially around the second ablation electrode 1302 in an evenly spaced manner. The main body 1304 may extend around each opening so as to be electrically continuous. The tines may be extensible or retractable tines to increase the electric field size of the ablation electrode and that allow the tines to be withdrawn from an initial low-profile intramyocardial delivery tract. For example, an outer sheath may be provided over the ablation microcatheter 102 that has an inner diameter that matches the outer diameter of the ablation microcatheter 102 but allows sliding of the ablation microcatheter 102 relative to the outer sheath. The outer sheath may extend at least along the second ablation electrode 1302 during delivery of the ablation microcatheter 102, may not include a tapered distal end, and may be positioned with its distal terminating end at approximately the first mapping electrode 104 during navigation of the ablation microcatheter 102 through the myocardium. Once at target, the outer sheath may be moved proximally to expose the second ablation electrode 1302 and allow the tines to move outward. After ablation, the outer sheath may be moved distally to reposition the tines in their respective openings.

[0053] FIG. 14 shows a third ablation electrode 1402 that may be incorporated into ablation microcatheter 102. Third ablation electrode 1402 may be positioned on the ablation microcatheter 102 similarly to ablation electrode 108, and may be comprised of the same material(s), have the same length, and have the same inner diameter as the ablation electrode 108. Rather than include a plurality of fenestrations, the third ablation electrode 1402 may include a plurality of electrode strips coupled between a first ring segment 1404 and a second ring segment 1406. For example, the plurality of electrode strips may include a first strip 1408 and a second strip 1410. Each strip may be electrically coupled to the first ring segment 1404 and the second ring segment 1406. Further, each strip may be bendable / flexible to allow the strips to move from being substantially straight to being bent outward, away from the central axis of the ablation microcatheter 102, to thereby form a plurality of clamshell-like openings. The ablation microcatheter 102 may includeAttorney Docket No. NIH24304PCT pull-cables or another actuation mechanism that, when actuated, pulls the first ring segment 1404 (and components of the ablation microcatheter 102 distal of the first ring segment 1404) closer to the second ring segment 1406. When the first ring segment 1404 and the second ring segment 1406 are at a maximum distance from each other, each strip of the plurality of strips is substantially straight (e.g., extends in parallel to the x axis) and in close alignment with neighboring strips along the outer circumference of the ablation microcatheter 102. When the first ring segment 1404 is moved closer to the second ring segment 1406, each strip of the plurality of strips bends outward to form an opening between each pair of neighboring strips, such as first opening 1412. The openings may be considered to have a clamshell-like shape due to the rounding upward and downward of the strips forming the openings. The size of each opening may be controlled by controlling the distance between the first ring segment 1404 and the second ring segment 1406. During navigation of the ablation microcatheter 102 to the target, the first ring segment 1404 may be held at the maximum distance from the second ring segment 1406 to keep the strips in the low- profile position for traversing the myocardium. Once at target, the first ring segment 1404 may be pulled proximally to create openings for irrigation and increase the electric field size of the ablation electrode.

[0054] In some examples, the ablation electrode may have spiral / helical and / or sinusoidal openings, which may be static openings (e.g., that are fixed in place) or dynamic openings (e.g., that can be exposed and closed). For example, FIG. 18 shows a fourth ablation electrode 1802 that may be incorporated into ablation microcatheter 102. Fourth ablation electrode 1802 may be positioned on the ablation microcatheter 102 similarly to ablation electrode 108, and may be comprised of the same material(s), have the same length, and have the same inner diameter as the ablation electrode 108. Similar to the third ablation electrode 1402, the fourth ablation electrode 1802 may include a plurality of electrode strips coupled between a first ring segment 1804 and a second ring segment 1806. For example, the plurality of electrode strips may include a first strip 1808 and a second strip 1810. Each strip may be electrically coupled to the first ring segment 1804 and the second ring segment 1806. However, unlike the strips of the third ablation electrode 1402, the strips of the fourth ablation electrode 1802 are wound partially around the central axis of the ablation electrode / ablation microcatheter. For example, the first strip 1808 may couple to the second ring segment 1806 at a first position and couple to the first ring segment 1804 at a secondAttorney Docket No. NIH24304PCT positon that is radially offset from the first position (e.g., by 180 degrees or another suitable amount).

[0055] Further, each strip may be bendable / flexible to allow the strips to move from being extended (e.g., at full length) to being bent outward, away from the central axis of the ablation microcatheter 102, to thereby form a plurality of helical-like openings. The ablation microcatheter 102 may include pull-cables or another actuation mechanism that, when actuated, pulls the first ring segment 1804 (and components of the ablation microcatheter 102 distal of the first ring segment 1804) closer to the second ring segment 1806. When the first ring segment 1804 and the second ring segment 1806 are at a maximum distance from each other, each strip of the plurality of strips is held in close alignment with neighboring strips along the outer circumference of the ablation microcatheter 102. When the first ring segment 1804 is moved closer to the second ring segment 1806, each strip of the plurality of strips bends outward to form an opening between each pair of neighboring strips, such as first opening 1812. The openings may be considered to have a helical-like shape due the winding of each opening around the central axis. The size of each opening may be controlled by controlling the distance between the first ring segment 1804 and the second ring segment 1806. During navigation of the ablation microcatheter 102 to the target, the first ring segment 1804 may be held at the maximum distance from the second ring segment 1806 to keep the strips in the low-profile position for traversing the myocardium. Once at target, the first ring segment 1804 may be pulled proximally to create openings for irrigation and increase the electric field size of the ablation electrode.

[0056] Still further examples of helical ablation electrode configurations are shown in FIGS. 19 and 20. FIG. 19 shows a fifth ablation electrode 1902 that may be incorporated into ablation microcatheter 102. Fifth ablation electrode 1902 may be positioned on the ablation microcatheter 102 similarly to ablation electrode 108, and may be comprised of the same material(s), have the same length, and have the same inner diameter as the ablation electrode 108. The fifth ablation electrode 1902 may be a helical electrode comprised of an electrode strip 1904 having a constant width that is wound around the central axis of the ablation microcatheter in a helical fashion. The electrode strip 1904 may extend continuously from a proximal end to a distal end of the fifth ablation electrode 1902. The helical winding of the electrode strip 1904 may create a continuous helical opening 1906 between turns of the electrode strip 1904. In the example shown in FIG. 19, the electrode strip 1904 may be wound relatively loosely to create a relatively large / wide helicalAttorney Docket No. NIH24304PCT opening 1906. For example, the helical opening 1906 may be such that, along an axis parallel to the x axis, the helical opening 1906 may have a first width W1 between two segments of the electrode strip 1904 that is equal to a second width W2 of the electrode strip 1904. Thus, the inner lumen of the ablation microcatheter 102 may be fluidly coupled to ambient via the helical opening 1906 and the amount of irrigant directed out of the fifth ablation electrode 1902 may be a function of the size of the helical opening 1906. Accordingly, the size of the helical opening may be selected based on desired irrigation properties during ablation, and the helical pitch of the electrode strip may be set to create the helical opening of the desired size. It is to be appreciated that the helical opening may be wider than shown in FIG. 19, or may be smaller, as shown in FIG. 20 and discussed below.

[0057] FIG. 20 shows a sixth ablation electrode 2002 that may be incorporated into ablation microcatheter 102. Sixth ablation electrode 2002 may be positioned on the ablation microcatheter 102 similarly to ablation electrode 108, and may be comprised of the same material(s), have the same length, and have the same inner diameter as the ablation electrode 108. The sixth ablation electrode 2002 may be a helical electrode comprised of an electrode strip 2004 having a constant width that is wound around the central axis of the ablation microcatheter in a helical fashion, similar to the fifth ablation electrode 1902, to create a continuous helical opening 2006 between turns of the electrode strip 2004. hi the example shown in FIG. 20, the electrode strip 2004 may be wound relatively tightly to create a relatively small helical opening 2006. For example, the helical opening 2006 may be such that, along an axis parallel to the x axis, the helical opening 2006 may have a first width W 1 between two segments of the electrode strip 2004 that is smaller than a second width W2 of the electrode strip 2004 (e.g., the second width W2 may be twice as large as the first width Wl, three times as large, or another suitable amount).

[0058] The example ablation electrodes shown in FIGS. 2, 13, 14, and 18-20 may be metal- only electrodes, such that the polymer tube does not extend coaxially with the ablation electrode. For example, FIG. 15 shows a cross-section of a portion of the ablation microcatheter 102 with the ablation electrode 108 taken along the x axis. FIG. 15 shows that the polymer tube terminates at the proximal end of the ablation electrode 108 (e.g., at the third insulating segment 205) and the distal end of the ablation electrode 108 (e.g., at the second insulating segment 204) and does not extend across the ablation electrode 108. However, other configurations are possible where theAttorney Docket No. NIH24304PCT polymer tube extends along the inner surface of the ablation electrode, as shown in FIGS. 16 and 17.

[0059] FIG. 16 shows a cross-section of a portion of the ablation microcatheter 102 with an ablation electrode 1608 taken along the x axis. In the example shown in FIG. 16, the ablation electrode 1608 is identical to ablation electrode 108, other than the ablation electrode 1608 has a smaller thickness, to thereby have a larger inner diameter than the inner diameter of the ablation electrode 108. The polymer tube includes a lining 1602 that lines the inner surface of the ablation electrode 1608 (e.g., an outer surface of the lining 1602 may be in face-sharing contact with the inner surface of the ablation electrode 1608). The lining 1602 may be in contact with and extend from the third insulating segment 205 and the second insulating segment 204. The lining 1602 may include fenestrations of the same size, shape, and placement of the fenestrations of the ablation electrode 1608 to ensure that the fluidic coupling between the inner lumen of the ablation microcatheter 102 and the area surrounding the ablation electrode 1608 is maintained. In the example of FIG. 16. the ablation electrode 1608 may have an inner diameter of 0.020 inches and an outer diameter of 0.025 inches and the lining 1602 may have an inner diameter of 0.015 inches and an outer diameter of 0.020 inches. It is to be appreciated that ablation electrode 1608 may be configured similarly to the second ablation electrode 1302, the third ablation electrode 1402, the fourth ablation electrode 1802, the fifth ablation electrode 1902, or the sixth ablation electrode 2002 and thus include openings of other size, shape, or placement than the fenestrations shown in FIG. 16. In such examples, the lining 1602 may include openings of the same size, shape, and placement of the openings of the ablation electrode 1608.

[0060] FIG. 17 shows a cross-section of a portion of the ablation microcatheter 102 with an ablation electrode 1708 taken along the x axis. In the example shown in FIG. 17, the ablation electrode 1708 is identical to ablation electrode 108, other than the ablation electrode 1708 has a smaller thickness, to thereby have a larger inner diameter than the inner diameter of the ablation electrode 108. The polymer tube includes a lining 1702 that lines the inner surface of the ablation electrode 1708 (e.g., an outer surface of the lining 1702 may be in face-sharing contact with the inner surface of the ablation electrode 1708). The lining 1702 may be in contact with and extend from the third insulating segment 205 and the second insulating segment 204. The lining 1702 may include fenestrations of the same size, shape, and placement of the fenestrations of the ablation electrode 1708 to ensure that the fluidic coupling between the inner lumen of the ablationAttorney Docket No. NIH24304PCT microcatheter 102 and the area surrounding the ablation electrode 1708 is maintained. In the example of FIG. 17, the ablation electrode 1708 may have an inner diameter of 0.024 inches and an outer diameter of 0.025 inches and the lining 1702 may have an inner diameter of 0.015 inches and an outer diameter of 0.024 inches. It is to be appreciated that ablation electrode 1708 may be configured similarly to the second ablation electrode 1302, the third ablation electrode 1402, the fourth ablation electrode 1802, the fifth ablation electrode 1902, or the sixth ablation electrode 2002 and thus include openings of other size, shape, or placement than the fenestrations shown in FIG. 17. In such examples, the lining 1702 may include openings of the same size, shape, and placement of the openings of the ablation electrode 1708.

[0061] Thus, in some examples, the polymer tube may extend across the ablation electrode and have a desired thickness; the outer diameter of the ablation microcatheter and the size of the inner lumen of the ablation microcatheter may be ensured by adjusting the thickness of the ablation electrode. For example, while example thicknesses are provided above, other thicknesses are possible without departing from the scope of this disclosure, such as the ablation electrode having an inner diameter of 0.018 inches and an outer diameter of 0.025 inches and the lining having an inner diameter of 0.015 inches and an outer diameter of 0.018 inches, or the ablation electrode having an inner diameter of 0.022 inches and an outer diameter of 0.025 inches and the lining having an inner diameter of 0.015 inches and an outer diameter of 0.022 inches. The segment of the polymer tube that extends across the ablation electrode (referred to above as the lining) may have openings that match the openings of the ablation electrode to facilitate irrigation via the ablation electrode. In some examples, the ablation electrode may be configured to rotate at least some around the central axis, which may thereby adjust the alignment between the openings of the lining and the openings of the ablation electrode, to provide a level of control over the amount of irrigation provided during ablation. The lining may be comprised of the same material as the polymer tube.

[0062] Thus, the catheter system described herein provides for coaxial arrangement of a 0.014" traversal and navigation guidewire (e.g., the navigation guidewire 110) and an -0.025" (typically 0.021-0.035") compatible tracking / infusion / ablation microcatheter (e.g., ablation microcatheter 102) with one or more mapping electrodes (e.g., the first mapping electrode 104 and the second mapping electrode 109) and a fenestrated / segmented ablation electrode (e.g., ablation electrode 108, second ablation electrode 1302, third ablation electrode 1402, fourth ablationAttorney Docket No. NIH24304PCT electrode 1802, fifth ablation electrode 1902, or sixth ablation electrode 2002). The ablation microcatheter may be low-profile, have a lumen for flowing irrigant and that tapers at a distal end to closely match the guidewire to deliver in coaxial fashion and to mitigate "size step-up" as the microcatheter is advanced over the coaxial guidewire, and have a braided metallic wire skeleton surrounded by electrically insulating and often lubricious polymer materials. Blood contacting surfaces of the microcatheter may be biocompatible. Polymers and / or markers of the microcatheter may be radiopaque to impart fluoroscopic conspicuity. The microcatheter may incorporate electrical transmission lines that convey biopotentials, current, ablative energy, or other electromagnetic signals to achieve ablation, biopotential measurement, and / or and electroanatomic tracking of the transmission line termini (e.g., the electrodes). The transmission lines may have shaped cross-sections. In particular, when the lining is provided that lines the ablation electrode, the electrical transmission lines may extend in the lining to electrically connect to elements distal of the ablation electrode (e.g., the first mapping electrode). In some examples, the polymer tube may include embedded metallic or non-metallic braiding or coils that are continuous or segmented to alter the mechanical performance of the ablation microcatheter. These braids or coils may include individually insulated metals that can serve as the transmission lines. The electrodes of the microcatheter may be short (l-2mm) for tracking or longer (5- 10mm) for tracking and RF ablation. The microcatheter may incorporate coils or braids to impart trackability and pushability and preservation of lumen dimensions during advancement along tortuous trajectories. The ablation microcatheter disclosed herein thereby incorporates irrigation opening(s) in an over-the-wire implementation, with an ablation electrode for intramyocardial ablation, tracking / mapping micro- coils / electrodes for E-field and B-field (electroanatomic) tracking, with a tapered nosecone configuration to allow delivery into the muscle of the beating heart.

[0063] The microcatheter may be comprised of a flexible catheter tube (e.g., the polymer tube described above) and an ablation electrode near the distal tip of the catheter tube, as explained above. The ablation electrode may include one or more openings. The catheter tube may be circumferential or non-circumferential and may have a rounded or tapered nosecone. The outer diameter of the catheter tube may be less than 3mm, and may preferably be 1.4-2.0 mm. The length of the catheter tube may be in a range of 100- 135cm, though other lengths are possible so long as the distal end of the catheter tube can reach an intramyocardial target of a patient while the proximal end remains outside the patient. The ablation electrode may have a length of 10mm. TheAttorney Docket No. NIH24304PCT ablation electrode may be segmented and thus include one or more openings / fenestrations that are open-cell; the electrode segments surrounding the openings may be electrically continuous with each other.

[0064] As explained above, the catheter tube is configured to track over a guidewire. The catheter tube may have an inner lumen that is larger than an outer diameter of the guidewire and the nosecone of the catheter tube may taper to have an inner diameter that substantially matches the outer diameter of the guidewire, to force delivery of fluid in the inner lumen out of the openings of the ablation electrode. Additionally or alternatively, the catheter tube may include slots, grooves, and / or channels on the inner surface of the catheter tube to allow delivery of fluid (such as along the guidewire) and reduce friction between the catheter tube and the guidewire. The slots, grooves, and / or channels may be etched, embedded, or glued in / to the inner surface of the catheter tube.

[0065] The openings in the ablation electrode may have a suitable / varied geometry, including circular, elliptical, polygonal, ogee, curved, sinusoidal, open-cell, closed-cell, rectangular, or curved slots, etc. This can be achieved through electrode configurations including closed-cell helices. Other electrode configurations may incorporate extensible or retractable tines to increase electric field size of ablation catheter that allows device to be withdrawn from initial low-profile intramyocardial delivery tract, or clamshell- or helical-like expansion / contraction via pull-cables. The ablation electrode may include tapered, feathered, helical, and / or dentate extensions that allow embedding into the adjoining catheter tube. The tapering is in any dimension but can especially be in the X-Y dimension so that the extensions can be covered by insulating polymer of the catheter tube. The ablation electrode may be coaxial with and around the catheter tube in any arrangement including the catheter tube being underneath the ablation electrode having any thickness including thickness=O (which would demand the edges of the tube and electrode to be connected edge-to- edge).

[0066] For example, the catheter tube may be constructed of successive (coaxial) layers added sequentially to alter the durometer of the catheter, and also may separately incorporate the tapered / feathered / helical extensions of the ablation electrode (and mapping electrodes) in different layers to impart trackability / flexibility / deliverability of the catheter. Similarly, the diameter of coaxial segments may be focally reduced by mechanical grinding, ablating, etching, stretching, or reflowing to allow application of the ablation electrode and mapping electrodes. Similarly, theAttorney Docket No. NIH24304PCT catheter tube may be constructed of lengthwise segments with multiple overlapping polymers of different composition and durometer to impart trackability / flexibility / deliverability of the catheter.

[0067] The ablation electrode may be constructed from heat-resistant, biocompatible and low impedance, electrically conductive materials such as copper, stainless steel alloy, platinum-iridium alloy, titanium, cobalt-chromium, or their gold-plated versions. Its fenestrated / segmented design allows for flexibility during delivery, adequate tissue contact for ablation, and tissue irrigation for temperature control and to alter the electrical characteristics of the interstitium. The baseline impedance of the ablation electrode is typically less than 300 ohms.

[0068] As explained above, the catheter tube may include / be coupled to one or more mapping electrodes, such as two mapping electrodes. The mapping electrodes are typically constructed from low impedance, electrically conductive materials such copper, stainless steel alloy, platinumiridium alloy, titanium, cobalt-chromium, or their gold-plated versions, ensuring efficient transmission of electrical signals for high-resolution cardiac mapping. These electrodes have impedance values typically less than 200 ohms. The mapping electrodes (typically l-2mm, typically ring electrodes but other shapes are possible, such as spiral, strips, partial rings, etc.), with or without the tapered / feathered / helical extensions, may be positioned immediately proximal and distal to the ablation electrode (typically separated by l-2mm) to allow ECG sensing and pacing and electroanatomic tracking on independent channels, via their transmission lines. When included, the tapered / feathered / helical extensions may enhance EAM tracking functionality

[0069] The ablation catheter system 100 may be used to perform intramyocardial ablation according to an example process 1000 shown in FIG. 10, which may be performed according to the method 1100 of FIG. 11. FIGS. 10 and 11 are described collectively below.

[0070] The process 1000 is performed on a heart of a human or non-human patient that includes a left ventricular cavity 1002, a right ventricular cavity 1004, myocardium 1006, and epicardium 1008. At 1102, method 1100 includes engaging one or more guiding catheters (e.g., transvenous, transarterial, or epicardial guiding catheter(s)) along the heart (e.g., myocardial) surface, which is shown at 1001 of FIG. 10. Engagement of the guiding catheters may include a curved or deflectable guiding sheath 1010 delivering a shaped guiding catheter (coaxial with the guiding sheath 1010 and thus not visible in FIG. 10) from a percutaneous venous access, such as the femoral vein, to the right ventricular septal endocardium (e.g., the endocardial surface of the septum). It is to be appreciated that in some examples, only the guiding sheath 1010 may be used,Attorney Docket No. NIH24304PCT or only the guiding catheter may be used. At 1104, method 1100 optionally includes stabilizing the system with an anchor, such as with an anchor guidewire. As shown at 1003 of FIG. 10, an anchor guidewire 1012 engages the interventricular septum through the guiding sheath 1010 and guiding catheter, and is steered across into the left ventricular cavity 1002. The anchor guidewire 1012 may be a 0.014" guidewire. The anchor guidewire 1012 may be ensnared to serve as an "anchor guidewire" that provides backup support to the guiding sheath and / or guiding catheter for all other intramyocardial catheter manipulation steps. Electrosurgical radiofrequency energy may be used to traverse the endocardial border if needed. Alternatively, in some examples, temporary intramyocardial or transmyocardial anchors that have helical screw or single / multiple fishhook loops may be used.

[0071] At 1106, method 1100 includes entering and navigating the myocardium with the VINTAGE coaxial catheter- wire system (e.g., the ablation catheter system 100) using EDEN, EAM, fluoroscopy, and intracardiac echocardiography. As shown at 1005 of FIG. 10, an ablation microcatheter 1016 and a navigation guidewire 1014 inside of the ablation microcatheter 1016 are delivered to the right ventricular septal endocardium via the guiding sheath 1010 and / or guiding catheter. The navigation guidewire 1014 is extended from this system to engage the myocardium. Electrosurgical radiofrequency energy may be used to traverse the endocardial border if needed. The catheter system (e.g., the navigation guidewire 1014 and the ablation microcatheter 1016) is advanced to the deep intramyocardial ablation target. At 1108, mapping and pace-mapping may be performed as desired to localize the VT circuit to identify the ablation target. Thus, components of the system may be used for determining functional characteristics of the target and nearby myocardium, for electroanatomic mapping of native and induced cardiac rhythms, and for ventricular stimulatory pulses to achieve pace-mapping of the target myocardium as appropriate. Multiple electrodes on the microcatheter and navigation guidewire may be combined as desired for multipolar mapping.

[0072] At 1110, deep intramyocardial irrigation is performed. In some examples, prior to performing irrigation, the ablation microcatheter may be adjusted to expose openings in the ablation electrode, such as by moving an outer sheath to allow tines of the ablation electrode to move outward and expose underlying openings for irrigation, or by actuating a pull-cable(s) to move the distal end of the ablation microcatheter closer to the proximal end and cause electrode strips of the ablation electrode to bend outward and form openings for irrigation. Once the ablationAttorney Docket No. NIH24304PCT electrode (e.g., on the ablation microcatheter 1016) is at the target, pre-irrigation is performed (e.g., with irrigant supplied via the lumen of the ablation microcatheter), typically with saline solution (0.45% - 0.9%), of the target ablation field via the fenestrations of the fenestrated ablation electrode of the ablation microcatheter 1016, embedded deep in the myocardium adjoining the target, beginning approximately one minute before RF ablation is instituted, at a suitable rate, such as a rate of ~2 mL / min, and continuing at the same rate until RF ablation is terminated. Irrigation may be performed with the navigation guidewire 1014 accommodated within the ablation microcatheter 1016 and with the navigation guidewire 1014 extending outward through the distal tip of the ablation microcatheter 1016, so that the irrigant is forced out of the openings of the ablation electrode and is blocked from exiting at the distal tip.

[0073] At 1112, method 1100 includes performing ablation during irrigation. As shown at 1007, the ablation electrode (e.g., of ablation microcatheter 1016) is used to apply RF, pulsed field, or microwave energy to the target myocardium, typically / optionally continuously guided by realtime impedance monitoring. In some examples, the following empirically derived target thresholds may be applied for the RF energy application and real-time impedance monitoring: expected drop from irrigation 5 to 25 ohms; expected drop from heating 10 to 15 ohms; expected threshold increase heralding steam pop: 18 ohms. Ranges of RF energy include 10 to 50 W. RF energy may be altered during ablation based on the above-mentioned empirical parameters.

[0074] The ablation electrode and / or microcatheter(s) may be repositioned and the mapping and ablation procedures repeated as needed, as indicated at 1114 of method 1100. At the conclusion of the procedure, the devices (e.g., the ablation microcatheter 1016 and the navigation guidewire 1014) are removed from the myocardium, the anchor guidewire 1012 removed, the guiding sheath 1010 and guiding catheter withdrawn, hemostasis achieved, and the procedure concluded.

[0075] Thus, the VINTAGE system disclosed herein (e.g., the ablation catheter system 100) allows access to deep myocardial targets that are inaccessible for ablation from the endocardial and epicardial surfaces, including the deep septum, LV summit, and papillary muscles. Some components of the VINTAGE system (e.g., the ablation microcatheter and / or the navigation guidewire) may include one or more mapping electrodes to enable EAM in order to identify targets for ablation as well as enable EDEN to guide desired positioning of the components in the myocardium. In particular, real-time imaging techniques such as x-ray fluoroscopy may provideAttorney Docket No. NIH24304PCT information regarding a longitudinal (e.g., base-to-apex) position and a circumferential (e.g., “clock-face”) position of the various components of the VINTAGE system in the heart, these techniques lack information regarding a radial position (also termed radial depth) of the microcatheters / guidewires within the myocardium. As used herein with respect to the heart, the terms “radial position” and “radial depth” denote a relative position in a single dimension between the endocardial and epicardial surfaces of the heart. Using EDEN, the radial depth of an intracardiac device (such as the ablation microcatheter and / or the navigation guidewire) may be classified according to its relative position between the endocardial and epicardial borders (or beyond) via a depth navigation classifier (which may be a machine learning or deep learning-based algorithm or a logic-based algorithm) that uses intramyocardial electrograms measured by an electrode of the intracardiac device itself. Different depths between the endocardial and epicardial borders of the myocardium and outside of the myocardium produce different characteristic electrogram waveform features. These waveform features may be extracted and used by the classifier (executed on a signal processor, e.g., a computing device) to differentiate between different radial depth categories.

[0076] In some examples, aspects of the VINTAGE system may be assembled into a kit 1200 as shown schematically in FIG. 12. The kit 1200 may include a packaging 1202 housing the ablation microcatheter 102 (including the first mapping electrode 104, an ablation electrode such as the ablation electrode 108, the second ablation electrode 1302, the third ablation electrode 1402, the fourth ablation electrode 1802, the fifth ablation electrode 1902, the sixth ablation electrode 2002, or any of the ablation electrodes 1608, 1708 and the second mapping electrode 109, one or more or each or none of which may include coupling extensions) and the navigation guidewire 110 (including the exposed conductor 111). In some examples, the packaging 1202 may be sterile packaging. In some examples, each of the ablation microcatheter 102 and the navigation guidewire 110 may be packaged in individual, sterile packages, and the packaging 1202 may not be sterile.

[0077] In some examples, the kit 1200 may include the guiding sheath 1010, a curved or deflectable guiding catheter 1204, and / or the anchor guidewire 1012. Further, in some examples, the kit 1200 may include one or more electrode connectors 1206. When the guiding sheath 1010, the guiding catheter 1204, the anchor guidewire 1012, and / or the one or more electrode connectors 1206 are included in the kit 1200, the guiding sheath 1010, the guiding catheter 1204, the anchor guidewire 1012, and / or the one or more electrode connectors 1206 may be included in packagingAttorney Docket No. NIH24304PCT1202 (and in some examples, at least the guiding sheath 1010, the guiding catheter 1204, and / or the anchor guidewire 1012 may be packaged in individual or common sterile packaging). In still further examples, the kit 1200 may include connectors, signal wires, and / or other components for connecting the ablation microcatheter and the navigation guidewire to an EAM and / or EDEN signal processor and / or for connecting the ablation microcatheter to the RF generator.

[0078] In some examples, the kit 1200 may include multiple ablation microcatheters and navigation guidewires, such as 5, 10, 25, 50, 100, or more of each of the ablation microcatheter and the navigation guidewire. In such examples, each individual component (e.g., each ablation microcatheter, each navigation guidewire) may be packaged in a separate sterile packaging and all housed within packaging 1202. Alternatively, one of each of the ablation microcatheter and the navigation guidewire may be packaged together in a common, sterile packaging to form a sub-kit, and a plurality of sub-kits (e.g., 5, 10, 25, 50, 100, etc.) may be packaged in packaging 1202. In examples where the kit 1200 includes the guiding sheath 1010, the guiding catheter 1204, the anchor guidewire 1012, and / or the one or more electrode connectors 1206, the kit 1200 may include multiple guiding sheaths, guiding catheters, and / or anchor guidewires (e.g., the same number as the number of ablation microcatheters), as well as multiple sets of the one or more electrode connectors 1206, packaged similarly to the ablation microcatheters and navigation guidewires (e.g., individually or in sub-kits).

[0079] Thus, current ablation therapy for VT, a common and life-threatening disease, are hampered by the relative inaccessibility of deep intramural myocardial targets for mapping and ablation. Arrhythmias originating from deep or anatomically inaccessible locations are hard to reach and treat by currently available technologies, accounting for a high rate of arrhythmia recurrence. The VINTAGE system disclosed herein addresses these issues by providing for ablation electrode navigation inside the beating ventricle and ablation inside the muscle, rather than from endocardial or epicardial surfaces, via delivery of RF energy using the ablation electrode of the ablation microcatheter inside the myocardium and intramyocardial irrigation inside the myocardium prior to and during ablation. The problem of ventricular arrhythmia critical circuit elements inaccessible to conventional endocardial or epicardial radiofrequency ablation is solved with the VINTAGE system by deep intramyocardial ablation electrode access and positioning combined with intramyocardial infiltrative irrigation through the fenestrations of the ablation electrode. The problem of navigating and positioning such deep intramyocardial ablationAttorney Docket No. NIH24304PCT electrodes is solved with the VINTAGE system by adding elements, for EDEN and for electroanatomic mapping and for multipolar intramyocardial pacing and mapping, to microcatheters and guidewires, which allows visualization and / or depth determination of the microcatheters and guidewires in tandem and relative to each other. The problem of insufficiently large ablation fields is solved with the VINTAGE system by deep intramyocardial infiltration by an intramyocardial infusion and ablation microcatheter larger than, and surrounding, the navigation guidewire. The ablation microcatheter may incorporate multiple features (e.g., fenestrated / segmented irrigation-ablation electrode and electromagnetic tracking and multipolar sensing / pacing elements) into a single over-the-wire catheter.

[0080] Thus, an over-the-wire microcatheter is disclosed herein, comprising an ablation electrode having fenestrations or other openings to allow intramyocardial irrigation; one or more mapping electrodes for intramyocardial unipolar or multipolar mapping, pacing, and registration with electroanatomic mapping; and a tapered distal end to allow delivery into the myocardium over a wire.

[0081] Characteristics of the microcatheter include biocompatibility and hemocompatibility, microcatheter hydrophilic material that allows tracking over the wire in the myocardium as well as flexibility, a Luer-Lock connector at the proximal hub to allow irrigation with pressurized fluid, and connections to the electroanatomic mapping system and ablation generator.

[0082] The microcatheter may have the following characteristics: an outer diameter of 0.025- 0.038"; an inner diameter 0.021-0.035" to accommodate an 0.014" guidewire and intramyocardial irrigation through the fenestrations / openings of the ablation electrode; a tapered tip to an inner diameter of 0.014-0.018" at the distal opening to track over the guidewire; a fenestrated / segmented ablation electrode that is 10-15 mm in length; at least two mapping electrodes (one on either side of the ablation electrode) that are 1-2 mm in length; and a usable length ranging between 135-175 cm. The microcatheter may optionally include longitudinal grooves inside the central lumen to enhance irrigation fluid delivery.

[0083] A method for VINTAGE using the herein described microcatheter use may include: percutaneous access to the femoral vein; engagement of the right ventricular septum using an appropriate catheter(s); right ventricular septum mechanical or electro surgical entry using a stiff 0.014" guidewire housed inside the microcatheter; navigation of the 0.014" wire within the myocardium in tandem with the microcatheter. Unipolar and multipolar electroanatomic mappingAttorney Docket No. NIH24304PCT using the guidewire and the microcatheter electrodes in tandem confirms navigation towards the area of interest. The mapping electrodes allow registration of the microcatheter in the electroanatomic map and electrogram sensing and pacing to confirm location of interest. Once at target, intramyocardial irrigation and ablation is performed through the fenestrated / segmented ablation electrode before and during radiofrequency ablation to expand the ablative electrical field.

[0084] Optionally, the electrodes may have “spiral” tails / extensions to ease bonding to the catheter shaft during manufacturing and thereby reduce risk of dislodgement / embolization. Additionally, the fenestrations may not be circular (e.g., the ablation electrode may include striplike openings or clamshell-like openings) and / or the fenestrations may be distributed to allow the electrode to be oriented to effect infiltration asymmetrically towards intended targets and thereby creating an asymmetric ablation field. Materials options include molybdenum-rhenium allows lower profile.

[0085] FIGS. 1-9 and 13-20 show example configurations with relative positioning of the various components. If shown directly contacting each other, or directly coupled, then such elements may be referred to as directly contacting or directly coupled, respectively, at least in one example. Similarly, elements shown contiguous or adjacent to one another may be contiguous or adjacent to each other, respectively, at least in one example. As an example, components laying in face-sharing contact with each other may be referred to as in face-sharing contact. As another example, elements positioned apart from each other with only a space there-between and no other components may be referred to as such, in at least one example. As yet another example, elements shown above / below one another, at opposite sides to one another, or to the left / right of one another may be referred to as such, relative to one another. Further, as shown in the figures, a topmost element or point of element may be referred to as a “top” of the component and a bottommost element or point of the element may be referred to as a “bottom” of the component, in at least one example. As used herein, top / bottom, upper / lower, above / below, may be relative to a vertical axis of the figures and used to describe positioning of elements of the figures relative to one another. As such, elements shown above other elements are positioned vertically above the other elements, in one example. As yet another example, shapes of the elements depicted within the figures may be referred to as having those shapes (e.g., such as being circular, straight, planar, curved, rounded, chamfered, angled, or the like). Further, elements shown intersecting one another may be referred to as intersecting elements or intersecting one another, in at least one example. Further still, anAttorney Docket No. NIH24304PCT element shown within another element or shown outside of another element may be referred as such, in one example.

[0086] The disclosure also provides support for a microcatheter for intramyocardial navigation and ablation, comprising: a flexible catheter tube, and a conductive ablation electrode positioned near a distal tip of the catheter tube, the ablation electrode including one or more openings to facilitate delivery of fluid out of the ablation electrode. In a first example of the microcatheter, the catheter tube and ablation electrode form an inner lumen configured to accommodate a navigation guidewire, the inner lumen having a first cross-sectional diameter that is larger than a second cross-sectional diameter of the navigation guidewire to allow the delivery of fluid through the inner lumen and out of the one or more openings of the ablation electrode. In a second example of the microcatheter, optionally including the first example, the catheter tube includes a tapered nosecone that tapers in cross-sectional diameter near and at the distal tip, such that a third cross-sectional diameter at the distal tip substantially matches the second cross- sectional diameter such that, when the navigation guidewire is accommodated in the catheter tube and extends outward from the distal tip, fluid delivery from the distal tip is blocked. In a third example of the microcatheter, optionally including one or both of the first and second examples, the catheter tube comprises one or more longitudinal grooves on an inner surface of the catheter tube to facilitate fluid flow along the navigation guidewire. In a fourth example of the microcatheter, optionally including one or more or each of the first through third examples, the ablation electrode comprises a first extension at a first end of the ablation electrode and a second extension at a second end of the ablation electrode, wherein the first extension is fully or partially embedded in a first section of the catheter tube and the second extension is fully or partially embedded in a second section of the catheter tube, wherein the first extension and the second extension each comprises a helical, feathered, dentate, and / or tapered segment. In a fifth example of the microcatheter, optionally including one or more or each of the first through fourth examples, the microcatheter further comprises: a first mapping electrode coupled to the catheter tube between the ablation electrode and the distal tip of the catheter tube and / or a second mapping electrode coupled to the catheter tube on a proximal side of the ablation electrode. In a sixth example of the microcatheter, optionally including one or more or each of the first through fifth examples, the first mapping electrode and / or the second mapping electrode comprises a surface ring electrode, a spiral electrode, one or more strips, or a partial ring electrode. In a seventh example of theAttorney Docket No. NIH24304PCT microcatheter, optionally including one or more or each of the first through sixth examples, the first mapping electrode includes a first extension at a first end of the first mapping electrode and a second extension at a second end of the first mapping electrode, wherein the first extension is fully or partially embedded in a first section of the catheter tube and the second extension is fully or partially embedded in a second section of the catheter tube, wherein the first extension and the second extension each comprises a helical, feathered, dentate, and / or tapered segment. In an eighth example of the microcatheter, optionally including one or more or each of the first through seventh examples, the microcatheter further comprises: a hub at a proximal end of the catheter tube, the hub including an irrigation port and a connector configured to couple the ablation electrode to a radiofrequency (RF), pulsed-field, or microwave generator. In a ninth example of the microcatheter, optionally including one or more or each of the first through eighth examples, the one or more openings include a plurality of fenestrations. In a tenth example of the microcatheter, optionally including one or more or each of the first through ninth examples, the ablation electrode includes one or more electrode strips, each electrode strip configured to extend along a longitudinal axis of the microcatheter in a first position and configured to bend outward to a second position to expose the one or more openings. In an eleventh example of the microcatheter, optionally including one or more or each of the first through tenth examples, the ablation electrode includes one or more electrode strips, each electrode strip winding at least partially around a longitudinal axis of the microcatheter, each electrode strip configured to bend outward from a first position to a second position to expose the one or more openings. In a twelfth example of the microcatheter, optionally including one or more or each of the first through eleventh examples, the one or more openings of the ablation electrode include a continuous helical opening formed by an electrode strip that winds around a longitudinal axis of the microcatheter in a helical fashion. In a thirteenth example of the microcatheter, optionally including one or more or each of the first through twelfth examples, the one or more openings of the ablation electrode are openings formed in a body of the ablation electrode, the body extending around each opening such that the ablation electrode is electrically continuous from a distal end of the ablation electrode to a proximal end of the ablation electrode.

[0087] This disclosure also provides support for a kit including the microcatheter above, optionally the microcatheter of one or more or each of the first through thirteenth examples, and aAttorney Docket No. NIH24304PCT navigation guidewire configured to be slidingly received by the microcatheter. In a first example of the kit, the navigation guidewire includes an insulated region and an uninsulated region.

[0088] The disclosure also provides support for a method for an ablation procedure, comprising: navigating an ablation microcatheter to an ablation target via a navigation guidewire, the navigation guidewire housed within the ablation microcatheter, the ablation microcatheter including an ablation electrode comprising one or more openings, wherein the one or more openings of the ablation electrode are openings formed in a body of the ablation electrode, the body extending around each opening such that the ablation electrode is electrically continuous from a distal end of the ablation electrode to a proximal end of the ablation electrode, with the navigation guidewire housed within the ablation microcatheter, irrigating the ablation target with an electrolyte via the one or more openings of the ablation microcatheter, and ablating the ablation target with radiofrequency (RF), pulsed-field, or microwave energy via the ablation electrode while continuing to irrigate the ablation target. In a first example of the method, navigating the ablation microcatheter to the ablation target comprises navigating the ablation microcatheter to the ablation target based on electrograms detected by one or more electrodes positioned on the navigation guidewire and / or the ablation microcatheter. In a second example of the method, optionally including the first example, navigating the ablation microcatheter to the ablation target comprises navigating the ablation microcatheter to the ablation target based on electromagnetic fields encoding spatial position and time from an electroanatomic mapping system detected by one or more electrodes positioned on the navigation guidewire and / or the ablation microcatheter. In a third example of the method, optionally including one or both of the first and second examples, ablating the ablation target with RF energy via the ablation electrode comprises activating an RF, pulsed-field, or microwave generator coupled to the ablation electrode.

[0089] As used herein, an element or step recited in the singular and preceded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. The terms “including” and “in which” are used as the plain-language equivalents of the respective termsAttorney Docket No. NIH24304PCT“comprising” and “wherein.” Moreover, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements or a particular positional order on their objects.

[0090] This written description uses examples to disclose the invention, including the best mode, and also to enable a person of ordinary skill in the relevant art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

Attorney Docket No. NIH24304PCTCLAIMS:

1. A microcatheter for intramyocardial navigation and ablation, comprising: a flexible catheter tube; and a conductive ablation electrode positioned near a distal tip of the catheter tube, the ablation electrode including one or more openings to facilitate delivery of fluid out of the ablation electrode.

2. The microcatheter of claim 1, wherein the catheter tube and ablation electrode form an inner lumen configured to accommodate a navigation guidewire, the inner lumen having a first cross-sectional diameter that is larger than a second cross-sectional diameter of the navigation guidewire to allow the delivery of fluid through the inner lumen and out of the one or more openings of the ablation electrode.

3. The microcatheter of claim 2, wherein the catheter tube includes a tapered nosecone that tapers in cross-sectional diameter near and at the distal tip, such that a third cross-sectional diameter at the distal tip substantially matches the second cross-sectional diameter such that, when the navigation guidewire is accommodated in the catheter tube and extends outward from the distal tip, fluid delivery from the distal tip is blocked.

4. The microcatheter of claim 2 or 3, wherein the catheter tube comprises one or more longitudinal grooves on an inner surface of the catheter tube to facilitate fluid flow along the navigation guidewire.

5. The microcatheter of any one of claims 1-4, wherein the ablation electrode comprises a first extension at a first end of the ablation electrode and a second extension at a second end of the ablation electrode, wherein the first extension is fully or partially embedded in a first section of the catheter tube and the second extension is fully or partially embedded in a second section of the catheter tube, wherein the first extension and the second extension each comprises a helical, feathered, dentate, and / or tapered segment.Attorney Docket No. NIH24304PCT6. The microcatheter of any one of claims 1-5, further comprising a first mapping electrode coupled to the catheter tube between the ablation electrode and the distal tip of the catheter tube and / or a second mapping electrode coupled to the catheter tube on a proximal side of the ablation electrode.

7. The microcatheter of claim 6, wherein the first mapping electrode and / or the second mapping electrode comprises a surface ring electrode, a spiral electrode, one or more strips, or a partial ring electrode.

8. The microcatheter of claim 6 or 7, wherein the first mapping electrode includes a first extension at a first end of the first mapping electrode and a second extension at a second end of the first mapping electrode, wherein the first extension is fully or partially embedded in a first section of the catheter tube and the second extension is fully or partially embedded in a second section of the catheter tube, wherein the first extension and the second extension each comprises a helical, feathered, dentate, and / or tapered segment.

9. The microcatheter of any one of claims 1-8, further comprising a hub at a proximal end of the catheter tube, the hub including an irrigation port and a connector configured to couple the ablation electrode to a radiofrequency (RF), pulsed-field. or microwave generator.

10. The microcatheter of any one of claims 1-9, wherein the one or more openings include a plurality of fenestrations.

11. The microcatheter of any one of claims 1-9, wherein the ablation electrode includes one or more electrode strips, each electrode strip configured to extend along a longitudinal axis of the microcatheter in a first position and configured to bend outward to a second position to expose the one or more openings.

12. The microcatheter of any one of claims 1-9, wherein the ablation electrode includes one or more electrode strips, each electrode strip winding at least partially around a longitudinal axis ofAttorney Docket No. NIH24304PCT the microcatheter, each electrode strip configured to bend outward from a first position to a second position to expose the one or more openings.

13. The microcatheter of any one of claims 1-9, wherein the one or more openings of the ablation electrode include a continuous helical opening formed by an electrode strip that winds around a longitudinal axis of the microcatheter in a helical fashion.

14. The microcatheter of any one of claims 1-13, wherein the one or more openings of the ablation electrode are openings formed in a body of the ablation electrode, the body extending around each opening such that the ablation electrode is electrically continuous from a distal end of the ablation electrode to a proximal end of the ablation electrode.

15. A kit for intramyocardial navigation and ablation, comprising: the microcatheter of any one of claims 1-14; and a navigation guidewire configured to be slidingly received by the microcatheter.

16. The kit of claim 15, wherein the navigation guide wire includes an insulated region and an uninsulated region.

17. A method for an ablation procedure, comprising: navigating an ablation microcatheter to an ablation target via a navigation guidewire, the navigation guidewire housed within the ablation microcatheter, the ablation microcatheter including an ablation electrode comprising one or more openings, wherein the one or more openings of the ablation electrode are openings formed in a body of the ablation electrode, the body extending around each opening such that the ablation electrode is electrically continuous from a distal end of the ablation electrode to a proximal end of the ablation electrode; with the navigation guidewire housed within the ablation microcatheter, irrigating the ablation target with an electrolyte via the one or more openings of the ablation microcatheter; and ablating the ablation target with radiofrequency (RF), pulsed-field, or microwave energy via the ablation electrode while continuing to irrigate the ablation target.Attorney Docket No. NIH24304PCT18. The method of claim 17, wherein navigating the ablation microcatheter to the ablation target comprises navigating the ablation microcatheter to the ablation target based on electrograms detected by one or more electrodes positioned on the navigation guidewire and / or the ablation microcatheter.

19. The method of claim 17 or 18, wherein navigating the ablation microcatheter to the ablation target comprises navigating the ablation microcatheter to the ablation target based on electromagnetic fields encoding spatial position and time from an electroanatomic mapping system detected by one or more electrodes positioned on the navigation guidewire and / or the ablation microcatheter.

20. The method of any one of claims 17-19, wherein ablating the ablation target with RF energy via the ablation electrode comprises activating an RF, pulsed-field, or microwave generator coupled to the ablation electrode.

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