Catheter tip insulator

Abstract

Various aspects of the present disclosure are directed to devices, systems, and methods that may include a cardiac ablation catheter. The cardiac ablation catheter may include a handle, a elongate shaft, and a distal assembly that includes a tip electrode, a ring electrode, and an insulator preform.

Description

Technical Field

[0001] The present disclosure relates to medical devices, systems, and methods for cardiac ablation. More specifically, the present disclosure relates to point pulse field ablation catheters.

Background Art

[0002] Ablation procedures are used to treat many different conditions in patients. Ablation can be used to treat cardiac arrhythmias, benign tumors, cancerous tumors, and to control bleeding during surgery. Typically, ablation is achieved by thermal ablation techniques including radiofrequency (RF) ablation and cryoablation. In RF ablation, a probe is inserted into the patient and high-frequency waves are transmitted through the probe to the surrounding tissue. The radiofrequency waves generate heat, and the heat destroys the surrounding tissue and cauterizes blood vessels. In cryoablation, a hollow needle or cryoprobe is inserted into the patient, and a cryogenic heat-conductive fluid is circulated through the probe to freeze and kill the surrounding tissue.

[0003] Another ablation technique uses electroporation. In electroporation or electropermeabilization, an electric field is applied to cells to increase the permeability of the cell membrane. Electroporation can be reversible or irreversible and depends on the strength of the electric field. When electroporation is reversible, the increased permeability of the cell membrane can be used to introduce chemicals, drugs, and / or deoxyribonucleic acid (DNA) into the cell before the cell heals and recovers. When electroporation is irreversible, the affected cells are killed by apoptosis.

[0004] Irreversible electroporation (IRE) can be used as a non-thermal ablation technique. In IRE, a short train of high-voltage pulses is used to generate an electric field strong enough to kill cells by apoptosis. In the ablation of cardiac tissue, IRE can be a safe and effective alternative to the indiscriminate killing of thermal ablation techniques such as RF ablation and cryoablation. IRE uses an electric field strength and duration that kill the target tissue but do not permanently damage other cells or tissues such as non-target myocardial tissue, red blood cells, vascular smooth muscle tissue, endothelial tissue, and nerve cells, and can be used to kill target tissues such as myocardial tissue.

[0005] There is a continuing need for an improved catheter device for performing IRE procedures. SUMMARY OF THE INVENTION

[0006] In Example 1, the cardiac ablation catheter comprises a elongate shaft and a distal assembly. The shaft has a proximal end and a distal end. The distal assembly has a proximal end and a distal end, and the proximal end is fixed to the distal end of the shaft. The distal assembly includes a tip electrode, a first ring electrode, and an insulator preform. The tip electrode is located at the distal end of the distal assembly. The first ring electrode is located proximal to the tip electrode and spaced apart from the tip electrode, and the first ring electrode has a distal tip and a proximal rear end. The insulator preform includes a proximal portion having a front portion defining a first diameter and a distal portion extending distally from the proximal portion, and the distal portion has a distal surface, a second diameter larger than the first diameter so as to define a radial shoulder, and a distal portion length. The tip electrode extends distally from the distal surface of the insulator preform, the first ring electrode is disposed on the proximal portion such that the distal tip of the ring electrode abuts the radial shoulder of the insulator preform, and the distal portion length defines the longitudinal spacing between the tip electrode and the distal tip of the first ring electrode.

[0007] In Example 2, in the cardiac ablation catheter of Example 1, the distal electrode includes a distal electrode shoulder that abuts against the distal surface of the insulator preform. In Example 3, in the cardiac ablation catheter of either Example 1 or 2, the distal portion of the insulator preform includes a distal opening in the distal surface.

[0008] In Example 4, in the cardiac ablation catheter of Example 3, the distal electrode includes an active portion having an active portion diameter and a distal electrode shank having a distal electrode shank diameter smaller than the active portion diameter, and the distal electrode shank is received within the distal opening in the distal surface of the insulator preform.

[0009] In Example 5, in the cardiac ablation catheter of any one of Examples 1 to 4, the distal assembly further includes a second ring electrode that is located proximal to the first ring electrode and longitudinally spaced from the first ring electrode.

[0010] In Example 6, in the cardiac ablation catheter of any one of Examples 1 to 5, the distal assembly further includes an insulating material disposed at least proximally to the first ring electrode. In Example 7, in the cardiac ablation catheter of Example 6, the insulating material is disposed between the first ring electrode and the second ring electrode.

[0011] In Example 8, in the cardiac ablation catheter of Example 7, the insulating material is formed by an overmolding process. In Example 9, in the cardiac ablation catheter of Example 8, the insulator preform includes first and second longitudinal channels that extend through the proximal portion to the distal portion of the insulator preform.

[0012] In Example 10, in the cardiac ablation catheter of Example 9, the insulating material extends around the distal electrode shank through the first and second longitudinal channels so as to fix the distal electrode to the insulator preform.

[0013] In Example 11, in the cardiac ablation catheter of Example 9, the distal end electrode shank includes a plurality of radial protrusions that abut against the inner surface of the distal portion of the insulator preform, and the insulating material encapsulates the radial protrusions in order to fix the distal end electrode to the insulator preform.

[0014] In Example 12, in the cardiac ablation catheter of any one of Examples 8 to 11, the distal end electrode shank includes a plurality of radial openings that extend inward. In Example 13, in the cardiac ablation catheter of Example 12, the insulating material extends through the radial openings in order to fix the insulator preform to the distal assembly.

[0015] In Example 14, in the cardiac ablation catheter of any one of Examples 1 to 13, the proximal portion of the insulator preform includes a proximal opening and a navigator sensor lumen that extends from the proximal opening and terminates at a blind hole.

[0016] In Example 15, in the cardiac ablation catheter of any one of Examples 1 to 14, the proximal portion of the insulator preform has a planar portion that defines a space for accommodating the attachment of a conductor to the first ring electrode.

[0017] In Example 16, the cardiac ablation catheter includes a handle, a long shaft, and a distal assembly. The shaft has a proximal end and a distal end, and the proximal end extends distally from the handle. The distal assembly has a proximal end and a distal end, and the proximal end is fixed to the distal end of the shaft. The distal assembly includes a tip electrode, a first ring electrode, and an insulator preform. The tip electrode is located at the distal end of the distal assembly. The first ring electrode is located proximally to the tip electrode and is spaced apart from the tip electrode. The first ring electrode has a distal tip and a proximal rear end. The insulator preform includes a proximal portion having a front portion defining a first diameter, and a distal portion extending distally from the proximal portion. The distal portion has a distal surface, a second diameter larger than the first diameter so as to define a radial shoulder, and a distal portion length. The tip electrode extends distally from the distal surface of the insulator preform. The first ring electrode is disposed on the proximal portion such that the distal tip of the ring electrode abuts against the radial shoulder of the insulator preform. The distal portion length defines the longitudinal spacing between the tip electrode and the distal tip of the first ring electrode.

[0018] In Example 17, in the cardiac ablation catheter of Example 16, the tip electrode includes a tip electrode shoulder that abuts against the distal surface of the insulator preform. In Example 18, in the cardiac ablation catheter of Example 17, the distal portion of the insulator preform includes a distal opening in the distal surface.

[0019] In Example 19, in the cardiac ablation catheter of Example 18, the tip electrode includes an active portion having an active portion diameter and a tip electrode shank having a tip electrode shank diameter smaller than the active portion diameter. The tip electrode shank is received within the distal opening in the distal surface of the insulator preform.

[0020] In Example 20, in the cardiac ablation catheter of Example 19, the distal assembly further includes a second ring electrode located proximally to the first ring electrode and longitudinally spaced apart from the first ring electrode.

[0021] In Example 21, in the cardiac ablation catheter of Example 20, the distal assembly further includes an insulating material disposed at least proximally to the first ring electrode. In Example 22, in the cardiac ablation catheter of Example 21, the insulating material is disposed between the first ring electrode and the second ring electrode.

[0022] In Example 23, in the cardiac ablation catheter of Example 22, the insulator preform includes first and second longitudinal channels that extend from the proximal portion through the insulator preform to the distal portion of the insulator preform.

[0023] In Example 24, in the cardiac ablation catheter of Example 23, the insulating material extends around the tip electrode shank through the first and second longitudinal channels so as to fix the tip electrode to the insulator preform.

[0024] In Example 25, in the cardiac ablation catheter of Example 23, the tip electrode shank includes a plurality of radial protrusions that abut against the inner surface of the distal portion of the insulator preform, and the insulating material encapsulates the radial protrusions to fix the tip electrode to the insulator preform.

[0025] In Example 26, in the cardiac ablation catheter of Example 22, the tip electrode shank includes a plurality of radial openings that extend inwardly, and the insulating material extends through the radial openings to fix the insulator preform to the distal assembly.

[0026] In Example 27, in the cardiac ablation catheter of Example 26, the proximal portion of the insulator preform includes a proximal opening and a navigator sensor lumen that extends from the proximal opening and terminates at a blind hole.

[0027] In Example 28, in the cardiac ablation catheter of Example 27, the proximal portion of the insulator preform has a planar portion that defines a space for accommodating the attachment of a conductor to the first ring electrode.

[0028] In Example 29, in an ablation electrode assembly for a pulsed field ablation catheter, the ablation electrode assembly includes an insulator preform, a tip electrode, and a ring electrode. The insulator preform includes a proximal portion having a front portion defining a first diameter and a distal portion extending distally from the proximal portion. The distal portion has a distal surface, a second diameter larger than the first diameter so as to define a radial shoulder, and a distal portion length. The tip electrode extends distally from the distal surface of the insulator preform. The ring electrode is disposed on the proximal portion of the insulator preform such that the distal tip of the ring electrode abuts against the radial shoulder of the insulator preform, and the distal portion length of the insulator preform defines a longitudinal spacing between the tip electrode and the distal tip of the first ring electrode.

[0029] In Example 30, in the ablation electrode assembly of Example 29, the tip electrode includes a tip electrode shoulder that abuts against the distal surface of the insulator preform. In Example 31, in the ablation electrode assembly of Example 30, the distal portion of the insulator preform includes a distal opening in the distal surface.

[0030] In Example 32, in the ablation electrode assembly of Example 31, the tip electrode includes an active portion having an active portion diameter and a tip electrode shank having a tip electrode shank diameter smaller than the active portion diameter. The tip electrode shank is received within the distal opening in the distal surface of the insulator preform.

[0031] In Example 33, in the cardiac ablation catheter of Example 29, the insulator preform includes first and second longitudinal channels extending through the proximal portion to the distal portion of the insulator preform. The insulating material extends around the tip electrode shank through the first and second longitudinal channels so as to fix the tip electrode to the insulator preform.

[0032] In Example 34, a method of fabricating an ablation electrode assembly of a cardiac ablation catheter, the method comprising providing an insulator preform including a proximal portion having a forward portion defining a first diameter and a distal portion extending distally from the proximal portion, the distal portion having a distal face with a distal opening, a second diameter larger than the first diameter so as to define a radial shoulder, and a distal portion length; fixing a tip electrode to the distal portion of the insulator preform such that the tip electrode extends distally from the distal face of the insulator preform; fixing a ring electrode onto the proximal portion of the insulator preform such that the distal tip of the ring electrode abuts against the radial shoulder of the insulator preform, the fixing being such that the distal portion length of the insulator preform defines a longitudinal spacing between the tip electrode and the distal tip of the first ring electrode.

[0033] In Example 35, in the method of Example 34, the tip electrode includes an active portion having an active portion diameter and a tip electrode shank having a tip electrode shank diameter smaller than the active portion diameter, and fixing the tip electrode to the insulator preform includes inserting the tip electrode shank into the distal opening of the distal face of the insulator preform.

[0034] Although multiple embodiments are disclosed, further other embodiments of the present invention will become apparent to those skilled in the art from the following "Modes for Carrying Out the Invention" which illustrate and describe exemplary embodiments of the present invention. Therefore, the drawings and the "Modes for Carrying Out the Invention" should be regarded as being essentially exemplary and not restrictive.

Brief Description of the Drawings

[0035]

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[0036] While the present invention is applicable to various modified and alternative forms, specific embodiments are shown by way of example in the drawings and will be described in detail below. However, the intention is not to limit the present invention to the specific embodiments described. On the contrary, the present invention is intended to embrace all modifications, equivalents, and alternative forms within the scope of the present invention as defined by the appended claims.

Best Mode for Carrying Out the Invention

[0037] The following detailed description is exemplary in nature and is in no way intended to limit the scope, applicability, or configuration of the present invention. Rather, the following description provides some practical illustrations for implementing exemplary embodiments of the present invention. Examples of configurations, materials, and / or dimensions are provided for the selected elements. Those skilled in the art will recognize that many of the described examples have various suitable alternatives.

[0038] When this term is used in this specification with respect to measurements (e.g., dimensions, characteristics, attributes, components, etc.) and ranges thereof of tangible objects (e.g., products, inventory, etc.) and / or intangible objects (e.g., data, electronic representations of currency, accounts, information, parts of things (e.g., percentages, fractions), calculations, data models, dynamic system models, algorithms, parameters, etc.), "about" and "approximately" include the stated measurement and also any measurement that is reasonably close to the stated measurement but may vary by a reasonably small amount due to measurement error, differences in measurement and / or manufacturing apparatus calibration, human error in reading and / or setting of measurements, adjustments made to optimize performance and / or structural parameters in consideration of other measurements (e.g., measurements associated with other things), specific implementation scenarios, improper adjustment and / or operation of things, settings, and / or measurements by persons, computing devices, and / or machines, system tolerances, control loops, machine learning, predictable variations (e.g., statistically insignificant variations, chaotic variations, instability of systems and / or models, etc.), preferences, and / or the like, as understood and readily ascertainable by one of ordinary skill in the art. They may be used interchangeably to refer to a measurement.

[0039] Exemplary methods may be represented by one or more drawings (e.g., flowcharts, communication flows, etc.), but the drawings should not be construed as implying any requirements for the various steps disclosed herein or a particular order among them. However, some specific embodiments may require a particular step and / or a particular order between specific steps, as may be explicitly described herein and / or as can be understood from the nature of the steps themselves (e.g., the execution of some steps may depend on the result of a previous step). Additionally, a "set", "subset", or "group" of items (e.g., inputs, algorithms, data values, etc.) may include one or more items, and similarly, a subset or subgroup of items may include one or more items. "Plurality" means two or more.

[0040] As used herein, the term "based on" is not meant to be limiting, but rather indicates that a determination, identification, prediction, calculation, etc. is performed by using, at least, the term following "based on" as an input. For example, predicting a result based on certain information can additionally or alternatively be made based on different information for the same determination.

[0041] Irreversible electroporation (IRE) uses short (e.g., 100 microsecond) pulses of high voltage to kill cells by apoptosis. IRE can be targeted to kill myocardium while sparing other adjacent tissues including esophageal vascular smooth muscle and endothelium. Failure of dielectric separation between ablation poles can cause therapeutic energy to shunt through the catheter rather than be delivered to the target tissue, and can result in unintentional arcs or localized high currents that can damage the catheter and / or, in some cases, the surrounding tissue. Accordingly, with the introduction of high voltage therapy used in IRE, there is a need for robust dielectric separation between circuits throughout the catheter, particularly in the tip region of the catheter where the therapy is delivered.

[0042] Current catheter processes rely on materials flowing to seal joints and prevent fluid paths between exposed conductors (i.e., reflowed joints and adhesive joints). In these processes, voids or air bubbles may form and can be difficult to identify.

[0043] At least some embodiments of the present disclosure are directed to providing a guaranteed insulating layer between all conductive surfaces and wires that are at a high potential relative to each other within the tip region of a catheter. In some embodiments, an electroporation ablation system includes a point electroporation ablation catheter having an insulator preform. As used herein, a point catheter refers to a catheter having a linear body that carries an ablation electrode. In embodiments, the point catheter has an ablation electrode towards its distal end.

[0044] FIG. 1 is a diagram showing an exemplary clinical setting 10 for treating a patient 20 and treating the heart 30 of the patient 20 using an electrophysiology system 50 according to an embodiment of the subject matter of the present disclosure. The electrophysiology system 50 includes an electroporation device 60 and an optional local magnetic field generator 80. The clinical setting 10 also includes additional devices such as an imaging device 94 (represented by a C-arm), and various controller elements configured to enable an operator to control various aspects of the electrophysiology system 50. As will be understood by those skilled in the art, the clinical setting 10 may have other components and component arrangements not shown in FIG. 1.

[0045] The electroporation device 60 includes a cardiac ablation catheter 105, an introducer sheath 110, a controller 90, and an electroporation generator 130. In an embodiment, the electroporation device 60 is configured to deliver electric field energy to a target tissue within the patient's heart 30 to create tissue apoptosis so that the tissue cannot conduct electrical signals. The controller 90 is configured to control the functional aspects of the electroporation device 60. In an embodiment, the controller 90 is configured to control the electroporation generator 130 to generate electrical pulses, for example, the magnitude, timing, and duration of the electrical pulses. In an embodiment, the electroporation generator 130 is operable as a pulse generator to generate a pulse sequence for supply to the cardiac ablation catheter 105.

[0046] In an embodiment, the introducer sheath 110 is operable to provide a delivery conduit through which the cardiac ablation catheter 105 can be deployed to a specific target site within the patient's heart 30. However, it will be understood that the introducer sheath 110 is shown and described herein in order to provide context for the entire electrophysiology system 50.

[0047] In the illustrated embodiment, the cardiac ablation catheter 105 includes a handle 105a, a elongate shaft 105b, and a distal assembly 150. As shown, the shaft has a distal end 105c and a proximal end 105d, and the proximal end 105d of the shaft 105b extends distally from the handle 105a. The handle 105a is configured to be operated by a user to position the distal assembly 150 at a desired anatomical location. The shaft 105b generally defines the longitudinal axis of the cardiac ablation catheter 105. The shaft 105b may include a shaped articulation joint for spinal reinforcement and steering ability. Further details may be found in U.S. Patent Application No. 63 / 129,960, which is hereby incorporated by reference in its entirety.

[0048] As shown, the distal assembly 150 is positioned at or proximal to the distal end 105a of the shaft 105b. In an embodiment, the distal assembly 150 is electrically coupled to an electroporation generator 130 to receive an electrical pulse sequence or train of pulses, thereby selectively generating an electric field for removing target tissue by irreversible electroporation.

[0049] In certain embodiments, the cardiac ablation catheter 105 is a point catheter that includes a linear body toward the distal end. In embodiments, the distal assembly 150 includes one or more electrodes disposed on the shaft 105b. In some implementations, the distal assembly 150 includes one or more electrode pairs. In some embodiments, the distal assembly 150 includes one or more ablation electrodes and one or more sensing electrodes. In a particular implementation, the distal assembly 150 includes a pair of ablation electrodes configured to generate an electric field sufficient for irreversible electroporation ablation. In some examples, the ablation electrode pair includes a tip electrode covering the distal end of the catheter 105 and a ring electrode disposed proximate to the tip electrode. As used herein, the ring electrode refers to an electrode having a ring shape. In some designs, the pair of ablation electrodes includes two ring electrodes disposed proximate to the distal end of the catheter 105.

[0050] In embodiments, the position and size of the electrodes are specifically designed to allow flexibility. For example, the electrodes are designed to be relatively short in length. As another example, the two electrodes have a relatively large spacing to allow flexibility and / or deflection. In some examples, the one or more electrodes include one or more pairs of ablation electrodes and one or more pairs of sensing electrodes. The sensing electrodes can be used to sense electrical signals related to the patient's heart, thereby enabling an operator or system to determine whether ablation has occurred. In some designs, electrical signals can be used to determine the position or proximity position of the cardiac ablation catheter 105. In some embodiments, other sensors such as force sensors, navigation sensors (e.g., 5 or 6 degree of freedom ("DoF") sensors) can be incorporated into the distal assembly 150.

[0051] In some embodiments, one or more sense electrodes provided on the cardiac ablation catheter 105 may measure an electrical signal and generate an output signal that can be processed by a controller (e.g., controller 90) to generate an electroanatomical map. In some examples, the electroanatomical map is generated prior to ablation to determine the electrical activity of the cardiac tissue within the target heart chamber. In some examples, the electroanatomical map is generated after ablation to verify the desired changes in the electrical activity of the ablated tissue and the entire heart chamber. The sense electrodes may be used to determine the position of the catheter 105 in the three-dimensional space within the body. For example, when an operator moves the catheter 105 within the patient's heart chamber, the boundaries of the catheter movement can be determined by the controller 90, which may include or be coupled to a mapping and navigation system to form the anatomical structure of the heart chamber. The anatomical structure of the heart chamber is used to facilitate navigation of the catheter 105 without using ionizing radiation such as fluoroscopy, to guide the ablation intervals, and to assist the operator in completely removing the target anatomical structure, and can be used to tag the ablation location when the ablation is complete.

[0052] According to an embodiment, various components of the electrophysiology system 50 (e.g., controller 90) may be implemented on one or more computing devices. The computing device may include any type of computing device suitable for implementing the embodiments of the present disclosure. Examples of computing devices include workstations, servers, laptops, portable devices, desktops, tablet computers, handheld devices, general-purpose graphics processing units (GPGPU), etc., all of which are contemplated within the scope of FIG. 1 in relation to the various components of the system 50.

[0053] In some embodiments, a computing device includes the following devices: a processor, a memory, input / output (I / O) ports, I / O components, and a bus that directly and / or indirectly couples the power supply. Any number of additional components, different components, and / or combinations of components may also be included in the computing device. The bus may represent one or more buses (e.g., an address bus, a data bus, or a combination thereof). Similarly, in some embodiments, a computing device may include several processors, several memory components, several I / O ports, several I / O components, and / or several power supplies. Additionally, any number of these components or combinations thereof may be distributed and / or replicated across several computing devices.

[0054] In some embodiments, system 50 includes one or more memories (not shown). The one or more memories include computer-readable media in the form of volatile and / or non-volatile memory, temporary and / or non-temporary storage media, and can be removable, non-removable, or a combination thereof. Examples of media include Random Access Memory (RAM), Read Only Memory (ROM), Electronically Erasable Programmable Read Only Memory (EEPROM), flash memory, optical or holographic media, magnetic cassettes, magnetic tapes, magnetic disk storage devices or other magnetic storage devices, data transmissions, and / or any other media that can be used to store information and can be accessed by a computing device, such as, for example, quantum state memory. In some embodiments, the one or more memories store computer-executable instructions for causing a processor (e.g., controller 90) to implement aspects of the embodiments of the system components discussed herein and / or to execute aspects of the embodiments of the methods and procedures discussed herein.

[0055] Computer-executable instructions can include, for example, program components such as computer code, machine-usable instructions, etc., that are capable of being executed by one or more processors associated with a computing device. The program components can be programmed using any number of different programming environments, including various languages, development kits, frameworks, etc. Some or all of the functions contemplated herein can also or alternatively be implemented in hardware and / or firmware.

[0056] In some embodiments, the memory may include a data repository implemented using any one of the configurations described below. The data repository may include random access memory, flat files, XML files, and / or one or more database servers or one or more database management systems (DBMSs) running on a data center. The database management system may be a relational (RDBMS), hierarchical (HDBMS), multidimensional (MDBMS), object-oriented (ODBMS or OODBMS), or object-relational (ORDBMS) database management system, etc. The data repository may be, for example, a single relational database. In some cases, the data repository may include multiple databases that can exchange and aggregate data by a data integration process or software application. In an exemplary embodiment, at least a portion of the data repository may be hosted in a cloud data center. In some cases, the data repository may be hosted on a single computer, server, storage device, cloud server, etc. In some other cases, the data repository may be hosted on a series of networked computers, servers, or devices. In some cases, the data repository may be hosted on a hierarchy of data storage devices including local, regional, and central.

[0057] The various components of system 50 may communicate or be coupled via a communication interface, for example, a wired or wireless interface. The communication interface includes, but is not limited to, any wired or wireless short-range and long-range communication interfaces. The wired interface may use cables, umbilicals, etc. The short-range communication interface may be, for example, a local area network (LAN), It can be an interface compliant with known communication standards such as ZigBee (registered trademark) or similar specifications based on Bluetooth (registered trademark) specifications, IEEE 702 specifications (e.g., IEEE 702.11), IEEE 702.15.4 specifications, or other public or proprietary wireless protocols. The long-distance communication interface can be, for example, a wide area network (WAN), a cellular network interface, a satellite communication interface, etc.

[0058] The communication interface can be either within a private computer network such as an intranet or on a public computer network such as the Internet.

[0059] As will be described in more detail elsewhere in this specification, various embodiments of the present disclosure, particularly the distal assembly 150, employ novel structural features to improve clinical performance and enhance the manufacturability of the ablation catheter 105. In particular, the distal assembly 150 includes an insulator preform that, among other things, supports and positions the tip electrode and the adjacent ring electrode and operates to electrically insulate the various electrical components of the distal assembly 150.

[0060] FIG. 2 is an isometric view of the distal portion of a cardiac ablation catheter 200. In an embodiment, the cardiac ablation catheter 200 corresponds to the ablation catheter 105 shown in FIG. 1 and includes a distal assembly 202.

[0061] As shown, the distal assembly 202 is axially disposed along a longitudinal axis 204 defined by a shaft of the ablation catheter 200 (not shown in FIG. 2). The distal assembly 202 includes a pair of electrodes 208 including a tip electrode 212 and a ring electrode 214, the tip electrode 212 being disposed at the distal end of the distal assembly 202, and the ring electrode 214 being located proximally of and spaced from the tip electrode 212. As shown, the ring electrode has a distal tip 214a and a proximal rear end 214b. In an embodiment, the distal assembly 202 may include an additional pair 210 of electrodes including additional electrodes, such as electrodes 216, 218 disposed proximally of and longitudinally spaced from electrodes 212 and 214. In other embodiments within the scope of the present disclosure, more or fewer electrodes may be used.

[0062] The specific operation of various electrodes (or electrode pairs) can vary depending on the specific clinical use of the ablation catheter 200. In embodiments, the electrodes 212, 214, 216, and 218 can be configured to operate as ablation electrodes, sensing electrodes, or both. For example, any or all of the electrodes 212, 214, 216, and 218 can be configured to be operable for delivering ablation energy to target tissue. Additionally or alternatively, any or all of the electrodes 212, 214, 216, and 218 can operate as sensing electrodes configured to sense electrical signals (e.g., an endogenous cardiac activation signal and / or an electric field generated by an injected current for use in impedance-based position tracking, tissue proximity or contact sensing, etc.). In one embodiment, a pair of electrodes 208 can be configured to operate as ablation electrodes for bipolar delivery of ablation energy, particularly pulsed field ablation energy for focal ablation of cardiac tissue. In embodiments, the electrodes 216, 218 can operate as sensing electrodes or, alternatively, as ablation electrodes. In some examples, a second pair of electrodes 210 can be configured to measure local impedance and act as a position sensor for sensing a local electric field in five degrees of freedom (e.g., five different motions - x, y, z, acceleration, and rotation). In embodiments, except as specifically described herein, the electrodes 212, 214, 216, and 218 can be configured according to that described in U.S. Patent Application No. 63 / 194,716, filed by the same applicant and having a co-pending and same filing date, which is hereby incorporated by reference in its entirety.

[0063] In one exemplary embodiment, the electrode pair 212 can be operated at a first polarity, and the electrode pair 210 can be operated at a second polarity opposite the first polarity, thereby defining an ablation vector and a corresponding electric field therebetween.

[0064] However, it should be emphasized that the present disclosure is not limited to the specific electrode configuration and number of electrodes shown in FIG. 2. Rather, one of ordinary skill in the art will understand that additional variations, such as electrode configuration and number of electrodes, may be used within the scope of the present disclosure.

[0065] In the illustrated embodiment, the distal assembly 202 further includes a steering ring 222 located at the proximal end of the distal assembly 202. The steering ring 222 is mechanically connected to one or more steering wires 224 connected to a steering mechanism located at the handle (not shown) of the ablation catheter 200 and is configured to enable a user to steer the catheter 200 during operation. It should be emphasized that the specific steering ring 222 shown in FIG. 2 is for illustrative purposes only and is in no way limiting. In general, mechanisms for implementing steerability or deflectability in ablation catheters are well known, and thus one of ordinary skill in the art will recognize that a wide range of steering techniques may be employed in the ablation catheter 200.

[0066] In an embodiment, as shown, the distal assembly 202 includes an insulator preform 220, a portion of which is located between the tip electrode 212 and the ring electrode 216. In the illustrated embodiment, the insulator preform 220 includes a distal portion 220a and a proximal portion 220b (partially shown in FIG. 2). As shown, the distal portion 220a defines a distal portion length L1. Further shown, the distal portion 220a of the preform 220 is disposed between the tip electrodes 212, and the ring electrode 214 is disposed over a portion of the proximal portion 220b such that the distal tip 214a of the ring electrode 214 abuts a radially outward shoulder of the insulator preform 220 (shown in FIGS. 3A-3C and FIG. 4). The distal portion length L1 defines a longitudinal spacing along the longitudinal axis 204 between the tip electrode 212 and the distal tip 214a of the ring electrode 214. In an embodiment, the insulator preform 220 provides an insulating layer between conductive surfaces and wires that are at a high electrical potential relative to each other within the tip region of the catheter. In various embodiments, the length L1 is in the range of about 0.5 to 4.5 mm. In certain embodiments, the length L1 is about 1 to 4 mm. In certain embodiments, the length L1 is about 2.5 mm to about 3.5 mm. In some embodiments, the length L1 is about 1 to 2 mm.

[0067] In some examples, the insulator preform provides means for routing a conductive wire 226 through the distal assembly 202. In some examples, the insulator preform provides secure placement features for the tip components to enable better component spacing and compatibility with subsequent process steps (i.e., conforming). In some examples, the insulator preform provides protection for components of a cardiac ablation catheter 200, such as a navigation sensor or thermocouple, between various use conditions.

[0068] In an embodiment, the distal assembly 202 includes an insulating material 230 that is disposed at least proximally to the ring electrode 214 and encapsulates and forms the outer insulating surface of the distal assembly 202. In an embodiment, the insulating material 230 is disposed between the ring electrodes 214 and 216. In an embodiment, the insulating material 230 is formed by an overmolding process. Alternatively, the insulating material 230 can be formed using a reflow process in which one or more tubular segments of insulating material are disposed around the distal assembly 202 that is partially assembled and then heated, as is known in the art. In an embodiment, employing an overmolding process to provide the insulating material 230 can have certain advantages, such as reducing or even eliminating the need for subsequent processing (such as completing the assembly process and injecting a medical adhesive to provide a fluid-tight connection between various components). The insulating material can be commercially available PeBAx® 55D and PelAthAne® 55D. Both materials can be used in an overmolding process and can be joined to a "epoxy bondable" wire insulator. PelAthAne can be adhered to the tip insulator using a primer (e.g., SivAte™ E610) and plasma. PeBAx can be adhered to the tip insulator using an adhesive (e.g., ThermediCs 1-MP) without plasma.

[0069] Figures 3A-3C are, respectively, an isometric view, a cross-sectional isometric view, and a plan view of an embodiment of an insulator preform 300 used in the distal assembly of the cardiac ablation catheter of FIG. 1 according to an embodiment of the present disclosure.

[0070] As shown, the insulator preform 300 includes a distal portion 302 having a distal portion length L1 and a proximal portion 304 having a diameter d2 and a proximal portion length L2. In the illustrated embodiment, the proximal portion 304 has a front portion 304f and a rear portion 304r that extends proximally with respect to the front portion 304f. In an embodiment, the rear portion 304r can be omitted.

[0071] As shown, the distal portion 302 extends distally from the front portion 304f of the proximal portion 304 and has a maximum diameter d1. In addition, the front portion 304f of the proximal portion 304 has a maximum diameter d2. Further shown, the diameter d1 of the distal portion 302 is greater than the diameter d2 of the front portion 304f of the proximal portion, thereby defining a radial shoulder 306 at the intersection of the distal portion 302 and the front portion 304f of the proximal portion. As further discussed elsewhere in this specification, the front portion 304f is dimensioned such that a ring electrode (e.g., the ring electrode 214 of FIG. 2) can be disposed thereon.

[0072] In embodiments, the distal portion 302 of the preform 300 is generally cylindrical and includes a distal surface 308 and a distal opening 310 within the distal surface 308, and the interior of the distal portion 302 defines a distal portion cavity 329. In the illustrated embodiment, the preform 300 includes longitudinal channels 312 and 314 that extend through the front portion 304f of the proximal portion 304 to the distal portion 302. When present as in the embodiments of FIGS. 3A-3C, the longitudinal channels 312 and 314 are designed to facilitate the penetration of an overmold material or an adhesive material through the front portion 304f into the distal portion cavity 329 to enhance the mechanical attachment of the tip electrode to the insulator preform 300 during the manufacture of the distal assembly of the ablation catheter. In embodiments, one or both of the longitudinal channels 312 and 314 may be omitted.

[0073] In some embodiments as shown, the rear portion 304r of the proximal portion 304 has a smaller diameter than the front portion 304f and includes one or more ribs 316. When present, the ribs 316 operate to enhance the mechanical retention of an overmold resin (i.e., the insulating material discussed in FIG. 2) or a medical adhesive during the manufacture of the distal assembly.

[0074] In an embodiment, the insulator preform 300 includes various structural features to facilitate positioning and orientation of electrodes such as the tip electrode 212 and the ring electrode 214 of FIG. 2, as well as connection of conductor wires to each electrode. In the illustrated embodiment, the front portion 304f of the proximal portion 304 includes a notch flat region 318 and a proximal wire slot 331 to enable attachment of a conductor wire to the ring electrode 214 (FIG. 2) and overflow of overmold resin (i.e., the insulating material discussed in FIG. 2). The notch flat region 318 is located in the ring electrode landing zone 320 of the front portion 304f of the proximal portion 304 to facilitate alignment of the ring electrode and the tip electrode. In an embodiment, the ring electrode landing zone 320 can be dimensioned to enable the overmold resin (i.e., the insulating material discussed in FIG. 2) to flow under the proximal end of the ring electrode to help form a robust connection. Similarly, in the illustrated embodiment, the preform 300 includes a distal wire slot 350 extending along the inside of the distal portion 302 to facilitate connection of a conductor wire to the tip electrode. In an embodiment, in addition to accommodating the aforementioned electrical connections, the proximal wire slot 331 and the distal wire slot 350 can assist in orienting the respective electrodes with respect to the preform 300. In the illustrated embodiment, the proximal portion 304 of the insulator preform 300 can include a proximal opening 326 and a navigator sensor lumen 328 extending from the proximal opening 326 and terminating at a closed end 330 to form a blind hole. When present, the navigator sensor lumen 328 can be sized and configured to receive a magnetic tracking sensor to enable magnetic localization of a corresponding ablation catheter. In yet other embodiments, the preform 300 can include additional structural features for accommodating additional sensors (e.g., temperature sensors, pressure sensors, etc.) and corresponding conductors. However, it is emphasized that including the aforementioned wire and sensor accommodation and orientation features is not a requirement of the present disclosure, and in embodiments, some or all of these features can be omitted or configured differently from the specific exemplary embodiments shown.

[0075] In various embodiments, referring to FIG. 2, the distal portion length L1 is selected to accurately define the desired spacing between the proximal edge of the rear end of the tip electrode 212 and the distal edge of the tip of the ring electrode 214, while at the same time providing the necessary electrical insulation between the two electrodes. Thus, the disclosed configuration advantageously provides a consistent and accurate electrode spacing, which can be particularly advantageous for use in a pulsed electric field ablation catheter.

[0076] In the embodiments of FIGS. 3A - 3C, the proximal portion length L2 is selected to optimize the overall stiffness of the corresponding distal assembly and the stress concentration in the ring electrode disposed on the proximal portion 304, while still providing a suitable structural material for accommodating attachment to the catheter shaft. Additionally, the small - diameter rear portion 304r of the proximal portion 304 provides sufficient spacing for an overmold resin (i.e., the insulating material discussed in FIG. 2) to flow around the various conductor wires and reduce fluid leakage during the overmold process.

[0077] In various embodiments, the insulator preform 300 can be made of any suitable biocompatible insulating material (e.g., plastic, ceramic, etc.) that provides the desired structural and dielectric properties required for a particular clinical use of the cardiac ablation catheter. In an embodiment, the preform 300 can be pre - fabricated using any number of manufacturing processes, for example, machined, molded, cast, or fabricated through an additive manufacturing process. In an embodiment, exemplary materials used for the preform 300 include, but are not limited to, polycarbonate that is transparent to enable UV - curable adhesives and is also machinable. The insulating material of the insulator preform 300 ensures dielectric insulation by separating the tip electrode, the ring electrode, and the navigation sensor (if present), and other electrical components independent of the overmold resin or reflow insulator (i.e., the insulating material discussed in FIG. 2).

[0078] FIG. 4 is a cross-sectional elevation view of a portion of a distal assembly corresponding to distal assembly 202 of FIG. 2 in a partially assembled state. As shown, distal assembly 202 includes an insulator preform 400 and a tip electrode 402 fixed thereto, and an electrical conductor wire 403 is fixed to tip electrode 402. As shown, tip electrode 402 extends distally from distal surface 404 of insulator preform 400. Tip electrode 402 includes a tip electrode shoulder 406 that abuts distal surface 404 of insulator preform 400. Tip electrode 402 has an active portion 408 having an active portion diameter d3 and a tip electrode shank 410 having a tip electrode shank diameter smaller than the active portion diameter. Tip electrode shank 410 is received within distal opening 412 of distal surface 404 of insulator preform 400. As described above, tip electrode shank 410 is fixed within the distal portion of insulator preform 400 via overmolded insulating material and / or an adhesive. In an embodiment, tip electrode shank 410 includes one or more radial protrusions 414 that abut the inner surface of distal portion 416 of the insulator preform. During the overmolding process, the insulating material encapsulates radial protrusions 414 to fix tip electrode 402 to insulator preform 400.

[0079] FIG. 5 is an elevation view of an insulator preform 500 for use in a distal assembly of the cardiac ablation catheter of FIG. 1 according to an alternative embodiment of the present disclosure. Generally, insulator preform 500 is substantially identical to insulator preform 300 described above, except as described in connection with FIG. 5. Accordingly, insulator preform 500 includes a distal portion 502 and a proximal portion 504 having a rear portion 504r including a proximal tapered portion 506. Tapered portion 506 may operate to reduce stress, for example, between preform 500 and overmolding materials used to encapsulate various internal components of the distal assembly in the final product, to provide stress relief.

[0080] FIG. 6 is an elevation view of an insulator preform 600 for use in the distal assembly of the heart ablation catheter of FIG. 1, according to an alternative embodiment of the present disclosure. Generally, as shown, the insulator preform 600 is substantially identical to the insulator preform 300 described above, except as described in connection with FIG. 6. Accordingly, the insulator preform 600 includes a distal portion 602 having a distal portion length L1 and a proximal portion 604 having a proximal portion length L2. Similar to the insulator preform 300, the proximal portion of the insulator preform 600 includes a front portion 604f and a rear portion 304r. The proximal portion length L2 is relatively long in this embodiment compared to that shown in FIGS. 3A-3C, thanks to the relatively elongated rear portion 604r as shown. The relatively long proximal portion 304 provides an increased volume for wire routing, inclusion of orientation features, and support of additional components, such as sensors, and also provides an increased surface area for attaching the distal assembly to the catheter shaft, for example, via the overmolding process described above.

[0081] Various embodiments of the distal assembly 202 (FIG. 2) may incorporate various distal tip electrodes 212. As will be appreciated by those skilled in the art, the distal tip electrodes 212 are advantageously composed of, or include, a material that is visible under fluoroscopy (i.e., a radiopaque material) to assist the clinician in positioning the tip electrode 212, and thus, other electrodes if present, inside the patient's anatomical structure. One commonly used material is a platinum iridium (Pt / Ir) alloy that is both radiopaque and conductive to enable the delivery of ablation energy to the target tissue. At the same time, Pt / Ir is a relatively expensive material, and thus, it may be advantageous to minimize the volume of such material within the tip electrode 212.

[0082] FIG. 7 is an isometric view of one exemplary tip electrode 700 that may correspond to the tip electrode 212 of FIG. 2. As shown in FIG. 7, the tip electrode 700 is a two-piece construction having a body 704 and an active shell 708 disposed on a portion of the body 704. Further shown, the body 704 has a proximal portion 712 and an opposite distal portion (not visible in FIG. 7), and the shell 708 is disposed on the distal portion. Further shown, a shank 716 having a plurality of apertures 718 extends from the proximal portion 712. In an embodiment, the shank 716 may be received within the distal portion of various insulator preforms described elsewhere herein to facilitate assembly of the tip electrode 700 to the insulator preform. Additionally, the apertures 718, if present, may receive attachment materials, such as medical adhesives or overmold materials, to enhance the mechanical attachment of the tip electrode 700 to the insulator preform. As will be appreciated by those skilled in the art, the apertures 718 are merely an example as one such fixation enhancement feature that may be employed, and are not required in all embodiments of the present disclosure.

[0083] In one embodiment, the body 704 is made of a relatively inexpensive non-metallic material (e.g., ceramic), while the shell 708 can be formed of a partially or wholly radiopaque and conductive material to facilitate visualization of the tip electrode 700 under fluoroscopy and can operate as an active electrode portion for delivery of ablation energy. The foregoing structure provides the required electrode function while simultaneously minimizing the volume of the relatively expensive radiopaque material (e.g., Pt / Ir) required for the radiopaque active portion. Since the body 704 is non-conductive, the embodiment of FIG. 7 includes one or more vias 720 extending through the body 704 to facilitate electrical connection between the active shell 708 and a conductive wire (not shown) for delivering ablation energy to the shell 708. In other embodiments, the body 704 can be formed of a conductive material (e.g., titanium) that has minimal radiopacity or no radiopacity but is relatively less expensive than a radiopaque material such as Pt / Ir. In such embodiments, the vias 720 can be omitted and the required electrical connection to the tip electrode 700 can be made directly to the body 704 (e.g., by attaching a conductive wire(s) directly to the shaft 716).

[0084] FIGS. 8A and 8B are isometric views of an alternative tip electrode 800 that can correspond to the tip electrode 212 of FIG. 2 according to some embodiments. Similar to the tip electrode 700, the tip electrode 800 is a two-piece structure that includes a body 804 and a radiopaque ring 808. FIG. 8A shows the assembled tip electrode 800, while FIG. 8B shows only the body 804 without the radiopaque ring 808.

[0085] As shown, the body 804 has a proximal portion 812 and an opposite distal portion 814. As can be seen in FIG. 8A, the proximal portion 812 has a diameter smaller than the maximum diameter of the distal portion 814 so as to define a shoulder 815 at the proximal end of the distal portion 814. In the assembled tip electrode 800, the radiopaque ring 808 is disposed on the proximal portion 812 and abuts against the shoulder 815. As a result, the assembled tip electrode 800 is substantially of equal diameter, i.e., the maximum diameters of the distal portion 814 and the radiopaque ring 808 are substantially the same so as to minimize the discontinuity between the distal portion 814 and the radiopaque ring 808.

[0086] As further shown, the body 804 includes a shank 816 extending from the proximal portion 812 having a plurality of ribs 818. In an embodiment, the shank 816 can be received within the distal portion of various insulator preforms described elsewhere herein to facilitate the assembly of the tip electrode 800 to the insulator preform. Additionally, the ribs 818, if present, can provide an increased surface area for attaching the shank 816 to the insulator preform, such as using a medical adhesive or overmold material, to enhance the mechanical attachment of the tip electrode 800 to the insulator preform. As further shown, in the illustrated embodiment, the shank 816 includes a flat region 820 to facilitate the attachment of a conductor wire to the tip electrode 800.

[0087] In an embodiment, the body 804 is a single-piece solid structure formed of a conductive but relatively inexpensive material (e.g., titanium), and the radiopaque ring 808 can be formed from a conductive and radiopaque material such as Pt / Ir. Similar to the tip electrode 700 described above, the design of the tip electrode 800 provides the desired visibility under fluoroscopy while reducing the volume of the relatively expensive radiopaque material utilized. In an embodiment, the radiopaque ring 808 can be attached to the body 804 using conventional manufacturing techniques (e.g., welding).

[0088] FIG. 9 is a cross-sectional perspective view of an alternative tip electrode 900 that may correspond to the tip electrode 212 of FIG. 2 according to some embodiments. As shown, the tip electrode 900 includes a body 904 and an outer shell 908 that together form the electrically active portion of the tip electrode 900. Further shown, the body 904 includes a proximal portion 912 and a distal portion 914, and the shell 908 is disposed over the distal portion 914. The proximal portion 912 has a maximum diameter that is larger than the maximum diameter of the distal portion 914 such that the proximal end of the distal portion 914 abuts a shoulder 915 that defines the proximal portion 912 in the assembled tip electrode 900. As a result, the assembled tip electrode 900 is substantially of equal diameter at the junction of the proximal portion 912 and the distal portion 914, i.e., the maximum diameters of the distal portion 914 and the proximal portion 912 are substantially the same so as to minimize the discontinuity between the distal portion 914 and the proximal portion 812.

[0089] Further shown, the body 904 includes a shank 916 extending from the proximal portion 912 having a plurality of openings 918 as well as ribs 920. In embodiments, the shank 916 may be received within the distal portion of various insulator preforms described elsewhere herein to facilitate assembly of the tip electrode 800 to the insulator preform. Additionally, the openings 918 and ribs 920, if present, may provide an increased surface area for attaching the shank 916 to the insulator preform, such as using a medical adhesive or overmold material, to enhance the mechanical attachment of the tip electrode 900 to the insulator preform. In embodiments, the shank 916 may also include features (not shown in FIG. 9) for positioning and attaching a conductor wire to the tip electrode 900.

[0090] In the embodiment of FIG. 9, the tip electrode 900 further includes a radiopaque ring 922 disposed between the distal portion 914 of the body 904 and the inner surface of the shell 908. In an embodiment, the body 904 can be constructed from a conductive but relatively inexpensive material (e.g., titanium), and the radiopaque ring 922 can be formed from a conductive and radiopaque material such as Pt / Ir. Similar to the tip electrodes 700 and 800 described above, the design of the tip electrode 900 provides the desired visibility under fluoroscopy while reducing the volume of the relatively expensive radiopaque material utilized. In an embodiment, the shell 908 and the radiopaque ring 922 can be attached to the body 904 using conventional manufacturing techniques (e.g., welding).

[0091] FIG. 10 is an elevation view of a handle 1000 that may correspond to the handle 105a of the cardiac ablation catheter 105 of FIG. 1 according to an embodiment of the present disclosure. As described elsewhere herein, the cardiac ablation catheter 105 (FIG. 1) may be a deflectable or steerable catheter, whereby the distal portion of the shaft can be selectively deflected or steered by a clinician as needed for the particular medical procedure being performed. The handle 1000 may be of a conventional design suitable for use in a deflectable ablation catheter, except for enhancements to receive relatively high (e.g., greater than 1000 V) DC voltages used in pulsed field ablation applications. As shown in FIG. 10, the handle 1000 includes a housing 1004 configured to be gripped by a clinician and a nose portion 1008 that operates as a transition section through which the catheter shaft and working components, such as electrical conductors, steering wires, etc., extend. In the illustrated embodiment, the handle 1000 further includes a double-wing deflection knob 1012 that is rotatable by a clinician to deflect the distal portion of the shaft in a manner known in the art. Additionally, the proximal end 1014 of the handle 1000 is adapted to enable the cardiac ablation catheter 105 to be operably coupled to an electroporation generator 130 (FIG. 1) and other components of the electrophysiology system 50 (FIG. 1) as a whole via a connector assembly 1018 (shown schematically in FIG. 10).

[0092] In an embodiment, the housing 1004 can be composed of two or more shell parts that are joined together to enclose various functional components disposed therein. The interfaces between the handle shell portion, the nose portion 1008, the deflection knob 1012, and the connector assembly 1018 can include gaps that, in conventional catheter handle designs, can create leakage paths into the interior of the handle 1000. In various embodiments of the present disclosure, the aforementioned interfaces are sealed using, for example, an epoxy potting material as exemplarily shown at 1024, to fill or substantially fill these gaps within the handle housing. In this way, potential leakage points into the interior of the handle that can be crosslinked by salts, moisture, etc. can be substantially sealed. In some embodiments, high voltage electrode wires (i.e., wires that are electrically coupled to the ablation electrode for delivery of high voltage PFA pulses) are routed through the handle 1000 to individual pin arrangements (not shown) for further electrical insulation from electrically erasable programmable read-only memory (EEPROM), navigation sensor wires, and other low voltage circuits.

[0093] The present invention is applicable to various modifications and alternative forms, but specific embodiments are shown by way of example in the drawings and are described in detail below. However, the intention is not to limit the present invention to the specific embodiments described. On the contrary, the present invention is intended to cover all modifications, equivalents, and alternative forms within the scope of the present invention as defined by the appended claims.

[0094] Various modifications and additions can be made to the exemplary embodiments described without departing from the scope of the present invention. For example, while the above embodiments refer to specific features, the scope of the present invention also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present invention is intended to cover all such alternative forms, modifications, and variations that fall within the scope of the claims, together with all of their equivalents.

Claims

1. A cardiac ablation catheter, comprising an elongate shaft having a proximal end and a distal end, a distal assembly having a proximal end and a distal end, the proximal end being fixed to the distal end of the shaft, the distal assembly comprising a tip electrode at the distal end of the distal assembly, a first ring electrode located proximal to and spaced from the tip electrode, the first ring electrode having a distal tip and a proximal rear end, an insulator preform including a proximal portion having a front portion defining a first diameter and a distal portion extending distally from the proximal portion, the distal portion having a distal surface, a second diameter larger than the first diameter so as to define a radial shoulder, and a distal portion length, and being provided with the tip electrode extending distally from the distal surface of the insulator preform, the first ring electrode being disposed on the proximal portion such that the distal tip of the first ring electrode abuts the radial shoulder of the insulator preform, the distal portion length defining a longitudinal spacing between the tip electrode and the distal tip of the first ring electrode, a cardiac ablation catheter.

2. The cardiac ablation catheter according to claim 1, wherein the tip electrode includes a tip electrode shoulder that abuts the distal surface of the insulator preform.

3. The cardiac ablation catheter according to claim 1 or 2, wherein the distal portion of the insulator preform includes a distal opening in the distal surface.

4. The tip electrode includes an active portion having an active portion diameter and a tip electrode shank having a tip electrode shank diameter smaller than the active portion diameter, and the tip electrode shank is received within the distal opening of the distal surface of the insulator preform. The cardiac ablation catheter according to claim 3.

5. The distal assembly further includes a second ring electrode positioned proximal to and longitudinally spaced from the first ring electrode. The cardiac ablation catheter according to any one of claims 1 to 4.

6. The distal assembly further includes an insulating material disposed at least proximally to the first ring electrode. The cardiac ablation catheter according to any one of claims 1 to 5.

7. The insulating material is disposed between the first ring electrode and the second ring electrode. The cardiac ablation catheter according to claim 6.

8. The insulating material is formed by an overmolding process. The cardiac ablation catheter according to claim 7.

9. The insulator preform includes first and second longitudinal channels extending through the proximal portion to the distal portion of the insulator preform. The cardiac ablation catheter according to claim 7.

10. The insulating material extends around the tip electrode shank through the first and second longitudinal channels so as to fix the tip electrode to the insulator preform. The cardiac ablation catheter according to claim 9.

11. The tip electrode shank includes a plurality of radial protrusions that abut against the inner surface of the distal portion of the insulator preform, and the insulating material encapsulates the radial protrusions to fix the tip electrode to the insulator preform. The cardiac ablation catheter according to claim 9.

12. The cardiac ablation catheter according to any one of claims 8 to 11, wherein the distal electrode shank includes a plurality of radially extending openings extending inwardly.

13. The cardiac ablation catheter according to claim 12, wherein the insulating material extends through the radially extending opening to fix the insulator preform to the distal assembly.

14. The cardiac ablation catheter according to any one of claims 1 to 13, wherein the proximal portion of the insulator preform includes a proximal opening and a navigator sensor lumen extending from the proximal opening and terminating at a stop hole.

15. The cardiac ablation catheter according to any one of claims 1 to 14, wherein the proximal portion of the insulator preform has a planar portion defining a space for accommodating the attachment of a conductor to the first ring electrode.

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