Heat transfer through the catheter tip

Abstract

To provide an electrophysiology catheter tip.SOLUTION: Described embodiments include a catheter tip including: an outer layer of a thermally conducting metal; an inner layer of a thermally conducting metal; a polymer layer between the inner and outer layers; and a plurality of thermal bridges selectively positioned between the inner and outer layers and through the polymer layer, thereby significantly increasing the heat transfer of the catheter tip through the polymer layer. Other embodiments are also described.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an ablation catheter and its use in ablation procedures.

Background Art

[0002] In some ablation procedures, an electrode disposed at the distal end of an ablation catheter is brought into contact with tissue, and then radiofrequency (RF) energy is passed from the electrode into the tissue. The RF energy raises the temperature of the tissue and thus causes damage within the tissue.

[0003] U.S. Patent Application Publication No. 2018 / 0110562, which is incorporated herein by reference, describes a catheter including an insertion tube, a flexible substrate, and one or more electrical devices. The insertion tube is configured to be inserted into a patient's body. The flexible substrate is configured to wrap around the distal end of the insertion tube and includes electrical interconnects. The electrical devices are coupled to the flexible substrate and are connected to the electrical interconnects.

Summary of the Invention

Means for Solving the Problems

[0004] According to some embodiments of the present disclosure, there is provided an electrophysiology catheter tip comprising a flexible thermally insulating substrate shaped to define (i) a plurality of narrow channels passing between an inner surface and an outer surface, and (ii) one or more wide channels passing between the inner surface and the outer surface. The tip further comprises an outer layer of conductive and thermally conductive metal covering at least a portion of the outer surface, an inner layer of conductive and thermally conductive metal covering at least a portion of the inner surface, a plating layer of conductive and thermally conductive metal plating the wide channels so as to connect the outer layer to the inner layer, and respective columns of thermally conductive metal filling the narrow channels so as to connect the outer layer to the inner layer.

[0005] In some embodiments, the substrate is shaped to define at least 1000 narrow channels.

[0006] In some embodiments, the total area of the outer openings of each of the narrow channels is at least 10% of the area of the outer surface.

[0007] In some embodiments, the conductive and thermally conductive metal includes gold.

[0008] In some embodiments, the tip further includes at least one constantan trace disposed on the inner surface and electrically insulated from the inner layer, and at least one gold trace disposed on the inner surface, electrically insulated from the inner layer, and covering the constantan trace at the thermocouple junction.

[0009] In some embodiments, the tip further includes a support structure coupled to the inner layer, and the substrate and the support structure are shaped to define an internal lumen.

[0010] In some embodiments, the substrate and the support structure are shaped to define a single including an internal lumen.

[0011] In some embodiments, the tip further comprises a catheter configured to be inserted into the body of a subject, and the support structure is coupled to the distal end of the catheter.

[0012] In some embodiments, the distal end of the catheter comprises a flow diverter configured to redirect the flow of fluid received from the proximal end of the catheter, and the support structure is coupled to the flow diverter such that the flow diverter is disposed within the internal lumen.

[0013] In some embodiments, the average diameter of each of the narrow channels is 5 to 50 micrometers.

[0014] In some embodiments, the average diameter of each narrow channel of the narrow 5-channel is less than 50% of the average diameter of each wide channel of the wide channel.

[0015] In some embodiments, the thickness of the substrate is 5 to 75 micrometers.

[0016] In some embodiments, the device further comprises one or more conductive traces disposed on the inner surface and electrically insulated from the inner layer, the substrate being shaped to define respective holes on the opposite side of the traces, and the outer layer comprising a main portion and one or more islands that are electrically insulated from the main portion and contact the traces respectively by at least partially filling the holes.

[0017] In some examples, an electrophysiological catheter tip comprising a substrate of an electrically and thermally insulating double metal layer, the outer layer of a thermally conductive metal, the inner layer of a thermally conductive metal, a polymer layer between the inner layer and the outer layer, and a plurality of heat bridges selectively disposed through the polymer layer between the inner layer and the outer layer, such that when about 0.63 amperes is delivered to the tip of the outer layer, at least about 100% improvement in ablation time is achieved that is considered clinically safe compared to a standard flex circuit ablation catheter with about 0.63 amperes, and when about 0.90 amperes is delivered to the outer layer of the tip, at least about 100% improvement in ablation time that is clinically safe is achieved compared to a standard flex circuit ablation catheter having an ablation current of about 0.90 amperes, an electrophysiological catheter tip is provided that increases heat transfer at the tip of the catheter through the polymer layer.

[0018] In some embodiments, the catheter tip comprises at least 1000 heat bridges.

[0019] In some embodiments, the heat bridge electrically and thermally joins the inner layer and the outer layer, thereby enabling heat transfer from the outside to the inside of the catheter tip, and the temperature can be cooled by the physiological saline used during perfusion.

[0020] In some embodiments, the heat bridge includes a solid cylinder and enables the perfusion fluid to transfer heat to the outside (e.g., the plated perfusion holes that transfer heat between the layer and the liquid).

[0021] In some embodiments, the diameter of the heat bridge is about 60 micrometers.

[0022] In some embodiments, the distance between the bridges is about 0.2 - 0.3 mm.

[0023] In some embodiments, the thermally conductive metals of the inner layer and the outer layer are the same material.

[0024] In some embodiments, the thermally conductive metals of the inner layer and the outer layer are different materials.

[0025] In some embodiments, the thermally conductive metals of the inner layer and the outer layer are gold and have a thickness of about 40 micrometers.

[0026] In some embodiments, the polymer layer is a printed circuit board (PCB) having a thickness of about 50 micrometers.

[0027] In some embodiments, the catheter tip is the distal tip of an ablation catheter and further includes a plurality of electrodes oriented to contact heart tissue and a plurality of perfusion holes between the inner layer and the outer layer.

[0028] In some embodiments, the perfusion holes include walls of thermally conductive metal plating.

[0029] In some embodiments, the thickness of the wall plating of the perfusion holes is about 25 micrometers.

[0030] In some embodiments, the catheter tip includes an overall shell thickness of about 130 micrometers.

[0031] In some embodiments, the catheter tip is configured to generate a hemispherical ablation site generated by heat with a radius of at least about 2 mm.

[0032] In some embodiments, it includes a cylindrical section and a dome section distal to the cylindrical section, and the thermal bridge is disposed within the cylindrical section and the dome section.

[0033] According to some embodiments of the present disclosure, inserting a distal end of a catheter including a substrate into the body of a subject, the substrate having an inner surface at least partially coated by an inner thermally conductive layer and an outer surface at least partially coated by an outer thermally conductive layer, the substrate being shaped to define (i) a plurality of narrow channels passing between the inner surface and the outer surface and filled by thermally conductive columns, and (ii) one or more plated wide channels passing between the inner surface and the outer surface. Further provided is a method including inserting. The method further includes contacting the tissue of the subject with the outer thermally conductive layer following insertion of the distal end of the catheter into the body of the subject. The method further includes passing an electric current through the outer thermally conductive layer (which can be on the order of 1 micrometer in height as long as it covers a thicker thermally conductive layer) while in contact with the tissue so that heat is generated in the tissue.

[0034] The method can provide an inner layer and / or an outer layer, as well as connection bridges and thermally plated perfusion channels, to act as a single thermally conductive structure so that heat is conducted from the tissue to the structure and convectively dissipated by the perfusion fluid and the blood in contact with the structure. In this example, when heat is mainly transferred from the central portion of the ablation, this reduces the hot spot temperature without adversely affecting the degree of thermal damage to the tissue.

[0035] In some embodiments, the tissue includes the heart tissue of interest.

[0036] In some embodiments, the outer tip layer includes a main portion and one or more islands that are electrically insulated from the main portion, and the method further includes using the islands to sense electrogram signals from the heart tissue.

[0037] According to some embodiments of the present disclosure, there is further provided a method including drilling a plurality of narrow channels and one or more wide channels through a flexible thermally insulating substrate to pass between the inner surface and the outer surface of the substrate. The method further includes using a thermally conductive material to at least partially coat the inner and outer surfaces, completely fill the narrow channels, and plate the wide channels.

[0038] In some embodiments, the method includes at least partially coating the inner and outer surfaces and completely filling the narrow channels, and plating the wide channels includes at least partially coating the inner and outer surfaces, completely filling the narrow channels, and depositing a thermally conductive material on the inner and outer surfaces of the substrate and in the narrow and wide channels to plate the wide channels, depositing a thermally conductive material on the inner surface of the substrate, and then plating the substrate in a plating bath of the thermally conductive material for a first time interval while the outer surface of the substrate is coated, plating the substrate for the first time interval, then at least partially exposing the outer surface of the substrate, and after at least partially exposing the outer surface of the substrate, plating the substrate in the plating bath for a second time interval.

[0039] In some embodiments, the method further includes coupling a thermally conductive material for coating the inner surface to a support structure and shaping the substrate and the support structure to define an internal lumen.

[0040] In some embodiments, forming the substrate and the support structure includes forming the substrate and the support structure to define a single body that includes an internal lumen.

[0041] In some embodiments, the method further includes etching one or more conductive traces on an inner surface of the substrate, and depositing a thermally conductive material on the inner surface of the substrate includes depositing the thermally conductive material on the inner surface of the substrate such that the conductive traces remain electrically insulated from the thermally conductive material, the method further includes forming holes on opposite sides of the traces of the substrate, and depositing a thermally conductive material on an outer surface of the substrate includes depositing the thermally conductive material on the outer surface of the substrate to form (i) a main portion and (ii) one or more islands that are electrically insulated from the main portion and that contact the traces by at least partially filling the holes.

[0042] According to some embodiments of the present disclosure, a method is further provided that includes inserting a distal end of a catheter into a subject's body, the distal end including an outer layer of a conductive and thermally conductive material, an inner layer of a thermally conductive material, a polymer layer between the inner layer and the outer layer, and a plurality of thermally conductive bridges selectively disposed between the inner layer and the outer layer through the polymer layer, thereby significantly increasing heat transfer of the catheter tip through the polymer layer, and subsequent to inserting the distal end of the catheter into the subject's body, contacting the subject's tissue with the outer layer, and passing an ablation current through the outer layer into the tissue while in contact with the tissue. A portion of the heat generated in the tissue is transferred to the thermal conduction layer of the thermal cross-bridge thermal conduction layer through the thermally conductive structures of the two layers (inner and outer) connected by the heat bridges and is finally convectively removed from the tip by the perfusion fluid and blood.

[0043] In some embodiments, the method further includes orienting the distal end of the catheter at a predetermined angle (e.g., 45°, 90°, etc.) with respect to the tissue, penetrating the tissue to a penetration depth, and ablating the tissue with ablation current / power at a predetermined safe temperature for a predetermined duration through the distal end of the catheter.

[0044] In some embodiments, the penetration depth of the catheter tip is about 0.8 mm.

[0045] In some embodiments, the step of ablating the tissue results in a damage depth of about 5.6 mm with an ablation current of about 0.63 amperes.

[0046] In some embodiments, the step of ablating the tissue results in a damage width of about 8.9 mm with an ablation current of about 0.63 amperes.

[0047] In some embodiments, the predetermined safe temperature is about 130°C or less.

[0048] In some embodiments, the predetermined duration is at least about 30 seconds and the ablation current is about 0.63 amperes, whereby the catheter maintains an ablation site at about 130°C or less throughout the ablation, thereby avoiding tissue rupture.

[0049] In some embodiments, the step of ablating the tissue provides at least about a 93% improvement in damage width over a standard flexible circuit ablation catheter with an ablation current of about 0.63 amperes.

[0050] In some embodiments, the step of ablating the tissue provides at least about a 500% improvement at clinically safe ablation times over a standard flexible circuit ablation catheter with an ablation current of about 0.63 amperes.

[0051] In some embodiments, the step of ablating tissue provides at least about 85% improvement in damage depth relative to a standard flexible circuit ablation catheter with an ablation current of about 0.63 amperes.

[0052] In some embodiments, the predetermined duration is at least about 5 seconds and the ablation current is about 0.90 amperes, whereby the catheter maintains an ablation site at about 130 °C or less throughout the ablation, thereby avoiding tissue rupture.

[0053] In some embodiments, the step of ablating tissue provides at least about 60% improvement in damage width relative to a standard flexible circuit ablation catheter with an ablation current of about 0.90 amperes.

[0054] In some embodiments, the step of ablating tissue provides at least about 160% improvement at clinically safe ablation times relative to a standard flexible circuit ablation catheter with an ablation current of about 0.90 amperes.

[0055] In some embodiments, the step of ablating tissue provides at least about 38% improvement in damage depth relative to a standard flexible circuit ablation catheter with an ablation current of about 0.90 amperes.

[0056] In some embodiments, the step of ablating tissue provides a damage depth of about 3.6 mm with an ablation current of about 0.90 amperes.

[0057] In some embodiments, the step of ablating tissue provides a damage width of about 6.9 mm with an ablation current of about 0.90 amperes.

[0058] According to some embodiments of the present disclosure, there is further provided a method including perforating a plurality of thermal bridges through a flexible thermally insulating polymer substrate and sandwiching the flexible thermally insulating polymer substrate between an inner surface and an outer surface using a thermally conductive metal.

[0059] In some embodiments, the step of perforating the thermal bridges includes perforating at least 1,000 thermal bridges.

[0060] In some embodiments, the method further includes perforating a plurality of perfusion holes through the inner layer, the outer layer, and the thermally insulating polymer substrate, and the perfusion holes have a diameter larger than that of the thermal bridges.

[0061] A more complete understanding of the present disclosure will be obtained by reading the following detailed description of the embodiments of the present disclosure in conjunction with the drawings.

Brief Description of the Drawings

[0062]

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Mode for Carrying Out the Invention

[0063] General Overview Embodiments of the present disclosure include ablation electrodes comprising at least one flexible printed circuit board (PCB) bonded to a metallic support sheet by an adhesive. The flexible PCB includes a flexible thermal insulation substrate, the outer surface of which is coated by an outer layer of a thermally conductive (and biocompatible) metal such as, for example, gold, palladium, or platinum, and an inner surface coated by an inner layer of the same (and / or another) thermally conductive metal. The inner surface may further support one or more electrical components such as sensors (e.g., thermocouples) and traces, electrically insulated from the inner metal layer. Following deposition of the electrical components, coating of the substrate, and bonding of the PCB to the support sheet, the flexible PCB (along with the support sheet) can be deformed into any suitable shape. For example, in some embodiments, the flexible PCB is deformed into a single-shaped electrode, hereinafter referred to as a “tip electrode”. The electrode is coupled to the distal end of a catheter.

[0064] During the ablation procedure, the outer thermally conductive layer is brought into contact with the tissue to be ablated, and then an ablation current is passed through the outer thermally conductive layer into the tissue. While the ablation current is applied to the tissue, the sensor may acquire any relevant physiological indices from the tissue. Typically, plated open vias penetrating the electrode provide an electrical connection between the inner and outer thermally conductive layers such that the ablation current can pass outwardly through the plated vias and the potential signal from the tissue can pass inwardly through the plated vias. The electrical connection can also be provided by blind vias, each of which is formed by removing a portion of the substrate such that the outer thermally conductive layer is in direct contact with the underlying trace.

[0065] The aforementioned plated vias also provide fluid communication between the inner and outer surfaces of the electrodes such that an infusion fluid (e.g., saline) can pass through the plated vias and into the surrounding blood. The infusion fluid dissipates heat from inside the electrode into the blood and further dilutes the blood at the tissue-electrode interface, reducing the likelihood of clot formation or burning. Due to the fact that the plated vias provide for the passage of the infusion fluid therethrough, the plated vias may also be referred to as “perfusion channels” or “perfusion holes”.

[0066] A problem with using electrodes of the above-described type is that the substrate may provide significant thermal resistance and limit the amount of heat transferred from the tissue-electrode interface into the interior of the electrode. When this occurs, the amount of heat that can be dissipated by the infusion fluid is limited.

[0067] To address this problem, embodiments described herein provide a large number (e.g., tens of thousands) of small closed vias (hereinafter referred to as “thermal vias”) to increase the thermal connectivity between the two surfaces of the electrode. Such thermal vias may include columns of a thermally conductive metal such as gold that connect an outer thermally conductive layer to an inner thermally conductive layer. Typically, the thermal vias are dispersed across the entire surface of the electrode. The thermal vias increase the amount of heat transferred into the interior of the electrode and thus facilitate heat dissipation by the infusion fluid.

[0068] Embodiments of the present disclosure also include a process for manufacturing the electrodes. Typically, both sides of the substrate are first coated with copper, and thus typically, the manufacturing of the electrodes begins by etching this copper except in locations where copper traces are required on the inner surface of the substrate. Next, a constantan trace used for the thermocouple is deposited on the inner surface. Subsequently, one or more wide channels, a large number of relatively narrow channels, and optionally, one or more blind vias are drilled through the substrate.

[0069] Subsequently, a mask is applied to the inner surface of the substrate over the traces and over the surrounding exclusion zones that insulate the traces from the inner thermally conductive layer. (However, the mask is not applied over the portions of the constantan traces designated as thermocouple junctions.) Similarly, another mask is applied to the outer surface over the exclusion zones that insulate the microelectrode "islands" from the remaining portion of the outer thermally conductive layer.

[0070] Next, a thin layer of metal (typically gold) is sputtered over the channels and both surfaces of the substrate. The metal sputtered onto the inner surface includes traces that cross the constantan traces and thus form thermocouple junctions. Following the sputtering of the metal, the mask is removed, the internal traces and exclusion zones are covered with another mask, and the entire outer surface is also masked.

[0071] Subsequently, the substrate is placed in a plating bath for a certain period of time to (i) cover any remaining exposed portions of the inner surface of the substrate with metal, i.e., extend the layer of metal laterally over the inner surface, (ii) increase the thickness of the inner layer, (iii) seal the narrow channels to serve as thermal vias, and (iv) narrow the wide channels to form plated perfusion channels. Then, the masks on the inner and outer surfaces are removed. Next, the internal traces and exclusion zones are covered by at least one coverlay.

[0072] Subsequently, the substrate is returned to the plating bath for a further period of time to increase the thickness of both the outer layer and the inner layer and narrow the plated perfusion channels. Typically, the total time the substrate is in the plating bath is set such that the thickness of the inner layer reaches the thickness of the coverlay. (Typically, the thickness of the outer layer is not increased significantly as this reduces the risk of cracking of the outer layer when the substrate is folded into its final shape.)

[0073] Next, for example, an opening having a diameter equal to or greater than the diameter of the irrigation hole is drilled in a metal support sheet including an alloy of cobalt and chromium. Next, the support sheet is bonded to the inner metal layer and the coverlay such that the opening of the support sheet is aligned with the irrigation channel of the substrate. Subsequently, the plated substrate and the support sheet are deformed into their desired shapes. Finally, a wire associated with the electrode is connected, and then the electrode is coupled to the catheter.

[0074] Description of the System First, referring to FIG. 1, this figure is a schematic diagram of a system 20 for ablating tissue of a target 26 according to some embodiments of the present disclosure.

[0075] FIG. 1 illustrates a physician 28 performing a unipolar ablation procedure on a target 26 using an ablation catheter 22. In this procedure, the physician 28 first inserts the distal tip 32 of the catheter 22 into the target, and then guides the distal tip 32 to the tissue to be ablated. For example, the physician may advance the distal tip through the target's vascular structure until the distal tip contacts heart tissue belonging to the target's heart 24. Next, while the distal tip 32 is in contact with the tissue, the physician passes a radiofrequency (RF) current between the distal tip 32 and an external neutral electrode patch 30 connected to, for example, the target's back.

[0076] To facilitate catheter guidance, the catheter 22 may include one or more electromagnetic position sensors that generate a signal that varies depending on the position of the sensor in the presence of an external magnetic field. Alternatively or additionally, any other suitable tracking system, such as an impedance-based tracking system, may be used. For example, both electromagnetic tracking and impedance-based tracking may be used as described, for example, in U.S. Patent No. 8,456,182, the disclosure of which is incorporated herein by reference.

[0077] The catheter 22 has its proximal end connected to the console 34, which includes, for example, a processor (PROC) 23, a pump 25, and a signal generator (GEN) 27. (The electrode patch 30 is also typically connected to the console 34 via a wire 42.) During the ablation procedure, the signal generator 27 generates the aforementioned ablation current. These currents are carried through the catheter 22 via one or more wires to the distal tip 32. In addition, the pump 25 supplies a perfusion fluid, such as saline, to the distal tip of the catheter, as will be further described below with reference to FIGS. 2A and 2B and FIG. 3.

[0078] The console 34 further includes an operating knob 35 that can be used by a physician to control the parameters of the ablation current. In particular, in response to the operation of the operating knob 35 by the physician 28, the processor 23 can adjust the parameters of the ablation current by outputting appropriate commands to the signal generator 27 via any suitable wired or wireless communication interface. The processor 23 can similarly control the pump 25 via any suitable wired or wireless interface. In addition, the processor can receive and process any relevant signals from the distal tip of the catheter, such as signals received from any of the sensors described herein.

[0079] In some embodiments, the system further includes a display 38 that can display relevant outputs to the physician 28 during the procedure.

[0080] Although FIG. 1 illustrates a particular type of procedure, it should be noted that the embodiments described herein can be applied to any suitable type of ablation procedure or any other procedure that requires heat transfer through a flexible PCB.

[0081] The distal tip of the catheter Referring now to FIG. 2A, this figure is a schematic view of the distal tip 32 according to some embodiments of the present disclosure. Further referring now to FIG. 3, this figure is a schematic longitudinal cross-sectional view through the distal tip 32 according to some embodiments of the present disclosure.

[0082] The distal tip 32 includes at least one ablation electrode 40, 30, such as the catheter tip electrode illustrated in FIGS. 2A and 3. The electrode 40 includes a plated flexible thermal insulating substrate 41 bonded to the support structure 36 at the distal end of the catheter 22 by an adhesive. The substrate 41 can be made of any suitable flexible thermal insulating material, such as a flexible polymer (e.g., polyimide) or a liquid crystal polymer (LCP). The support structure 36 can be made of any suitable strong material, such as cobalt chromium, stainless steel, magnesium, and / or any alloy of the foregoing. For example, the support structure 36 can include an L-605 cobalt-chromium-tungsten-nickel alloy.

[0083] Generally, the electrode 40 can have any suitable shape. In some embodiments, as shown in FIGS. 2A and 3, the electrode 40 has a single shape that includes a cylindrical portion 40b capped by a dome-shaped portion 40a. Typically, a tab 47 at the proximal end of the electrode includes a soldering pad to which a wire extending along the entire length of the catheter can be soldered to establish an electrical connection between the electrode and the proximal end of the catheter. These soldering pads are described in more detail below with reference to FIGS. 4 and 5.

[0084] As shown in the cross-sectional view taken along line “A-A” of FIG. 2A, the substrate 41 has an inner surface 76 facing the support structure 36 and an outer surface 45 facing away from the support structure 36. Typically, the thickness T0 of the substrate (i.e., the distance between the inner surface and the outer surface of the substrate) is 5 to 75 (e.g., 12 to 50) micrometers. At least a part of the inner surface is coated with an inner layer 70 of a thermally conductive metal such as gold. Typically, the inner layer 70 has a thickness T1 of 10 to 50 micrometers. Similarly, at least a part of the outer surface 45 is coated with an outer layer 50 of metal. Typically, the outer layer 50 has a thickness T2 of 1 to 5 micrometers.

[0085] Typically, the outer layer 50 is discontinuous in that it includes a main portion 54 and one or more insulating portions that are electrically insulated from the main portion 54 by exposed portions of the substrate. These insulating portions may include one or more “islands” that function as sensing microelectrodes 56. For example, the outer layer 50 may include 3 to 7 microelectrodes 56 distributed around the distal tip. Alternatively or additionally, the insulating portion may include a sensing ring electrode 43 that may be disposed, for example, near the proximal end of the distal tip 32.

[0086] Each conductive trace 78, which is electrically insulated from the inner layer 70 by an exposed portion of the inner surface 76, is disposed beneath each of the sensing electrodes. As will be further described below with reference to FIG. 4, prior to the formation of the sensing electrodes, holes, herein referred to as blind vias 80, are formed (e.g., drilled) in the substrate above the traces 78. Subsequently, when the sensing electrodes are deposited on the outer surface of the substrate, the sensing electrodes at least partially fill the blind vias 80 and thereby contact the traces.

[0087] Thus, during treatment, the potential signal from the target heart tissue sensed by the sensing electrodes can be conveyed via the traces 78 to a wire that extends through the catheter 22 to the proximal end of the catheter. In this way, the signal can be delivered to the processor 23 for analysis.

[0088] Referring now further to FIG. 2B, which schematically illustrates a cross-section of a portion of the electrode 40 according to some embodiments of the present disclosure. FIG. 2B corresponds to the "B-B" cross-section shown in FIG. 2A.

[0089] The substrate 41 is shaped to define a plurality of channels that pass between the inner and outer surfaces of the substrate, and the plurality of channels include a plurality of narrow channels 46 and one or more wider channels 44. Typically, each channel is tapered along the length direction of the channel, and the cross-sectional area of the channel at the inner surface of the substrate is slightly larger than the cross-sectional area at the outer surface. The cross-sectional area (or average cross-sectional area) of each narrow channel 46 is smaller than the cross-sectional area of each wide channel 44.

[0090] In some embodiments, the channels have a circular cross-section. In such embodiments, the average diameter d0 of each narrow channel can be less than 50% (e.g., less than 25%) of the average diameter d1 of each wide channel. Alternatively or additionally, the diameter d0 can be 5 to 50 micrometers (e.g., 5 to 30 micrometers), and / or the diameter d1 can be 50 to 300 micrometers. In other embodiments, at least a portion of the channels may have a cross-section having a square shape or any other suitable shape. (In such embodiments, the average cross-sectional area of each channel can correspond to that suggested above by the ranges of d0 and d1.)

[0091] Typically, the electrodes include broad channels from 30 to 100. Each broad channel 44 is plated by a conductive and thermally conductive metal plating layer 52, and the plating layer 52 connects the outer layer 50 to the inner layer 70. The plated broad channels thus provide conductivity and thermal conductivity between the outer and inner metal layers. Further, the plated broad channels provide a fluid passage between the interior and exterior of the distal tip 32, and the perfusion fluid 39 supplied by the pump 25 (see FIG. 1) can flow through the fluid passage. Thus, the plated broad channels can be referred to as "perfusion holes" 72. (The diameter of each perfusion hole is smaller than the diameter d1 by an amount corresponding to approximately twice the thickness of the plating layer 52.) The support structure 36 is shaped to define an opening 62 that is aligned with the perfusion hole 72 so that the support structure does not interfere with the perfusion hole.

[0092] Typically, the number of narrow channels 46 is relatively large. For example, the substrate 41 can be shaped to define at least 1000, 5000, 10000, or 20000 narrow channels. Alternatively or additionally, the ratio of the number of narrow channels to the number of broad channels can be at least 300:1. Alternatively or additionally, the total area of the outer openings of each narrow channel (i.e., the openings of the narrow channels on the outer surface of the substrate) can be at least 10%, 20%, or 30% of the area of the outer surface of the substrate. Thus, for example, if the area of the outer surface of the substrate (including the narrow channels) is 27 mm 2 and each narrow channel has a diameter of 25 micrometers (thus, an area of 0.0005 mm 2 ), the number of narrow channels can be approximately 16500 (total area 8.1 mm 2 ), and the outer openings of the narrow channels cover approximately 30% of the outer surface.

[0093] In contrast to the wide channels, the narrow channels 46 are not merely plated, but rather are filled by respective columns 48 of thermally conductive metal that connect the outer layer 50 to the inner layer 70. (The columns 48 are not necessarily cylindrical, as the narrow channels 46, as noted above, do not necessarily have a circular cross-section. Further, as noted above, the cross-sectional area of each column can vary along the length of the 15 columns.)

[0094] Note that the outer layer 50, inner layer 70, plating layer 52, and columns 48 can be described as a single unit of metal that coats the substrate. By virtue of the numerous channels 46 and the filling of each of these channels, a large amount of heat can be transferred through the channels 46. Thus, the filled narrow channels can be referred to as "thermal vias" 74. (For ease of illustration, the "A-A" cross-section of FIG. 2A does not show the thermal vias.)

[0095] Notwithstanding the above, it should be noted that in some embodiments, the narrow channels are not filled, but rather are merely plated as in the case of the wide channels. Even in such embodiments, a large amount of heat can be transferred into the electrodes.

[0096] Typically, the catheter 22 includes a fluid supply tube (not shown) that extends through the entire length of the tubular body 22m of the catheter 22. The distal side of the fluid supply tube is connected to a flow diverter 60 shaped to define one or more fluid flow openings 64. The flow diverter 60 changes the direction of the fluid 39 received through the fluid supply tube from the proximal end of the catheter through the fluid flow openings 64. In such embodiments, the electrode 40 can be connected to the base 58 of the flow diverter 60 such that the flow diverter is disposed inside the inner lumen of the electrode. For example, the support structure 36 can be coupled to the base 58. Alternatively or additionally, the base 58 can be shaped to define a plurality of protrusions, and the support structure 36 can be shaped to define a plurality of complementary holes such that the protrusions snap fit into the holes.

[0097] As previously described with reference to FIG. 1, during the ablation procedure, physician 28 contacts the distal tip 32, particularly the outer layer 50, with the tissue of subject 26. While contacting the tissue with the outer layer 50, the physician passes an electric current through the tissue via the outer layer. The electric current generates heat within the tissue such that damage is formed within the tissue. This heat is transmitted to the inner layer 70 via the heat vias 74 (i.e., via the columns 48). Simultaneously, pump 25 (FIG. 1) pumps perfusion fluid 39 through the fluid supply tube and into the interior of the electrode through the fluid flow opening 64 of the flow diverter 60. This fluid then exits the distal tip through the openings 62 and the perfusion holes 72, thereby discharging heat from the inner layer 70 to the blood of the subject.

[0098] Manufacture of the Distal Tip Next, referring to FIG. 4, which is a flowchart of a method 400 for manufacturing an electrode 40 according to some embodiments of the present disclosure. Further referring to FIG. 5, which is a schematic view of the electrode 40 before deformation according to some embodiments of the present disclosure. (FIG. 5 shows various elements connected to the interior of the electrode 40, i.e., the inner surface of the substrate 41.)

[0099] FIG. 4 assumes that at least the inner surface of the substrate is initially coated with a layer of copper. Thus, method 400 begins with an etching step 84 in which all of the copper is etched away from the inner surface, except for the copper trace 114 that is to be connected to the sense electrode outside the electrode. (Any copper on the outer surface is also etched away.) This etching can be performed, for example, by placing a mask over the portion of copper designated for the trace 114 and then chemically removing the exposed copper. Alternatively, if the inner surface of the substrate is initially exposed, the copper trace 114 can be deposited on the inner surface.

[0100] Subsequently, in the trace deposition step 86, a constantan trace 118 used for the thermocouple is deposited on the inner surface of the substrate. The trace deposition step 86 can be performed by physical vapor deposition (PVD) such as sputtering deposition. For example, a mask can be placed over the entire inner surface except for the portion of the inner surface designated for the constantan trace 118. Subsequently, a seed layer of a base metal such as titanium tungsten can be sputtered onto the substrate. Finally, constantan can be sputtered onto the base metal.

[0101] Typically, to minimize the required wiring, the constantan trace terminates at a common constantan trace soldering pad 120. In some embodiments, prior to the deposition of the constantan, holes (or "vias") are drilled into the substrate at the location of the soldering pads 120. Subsequently, the deposited constantan is filled into the holes, and then soldering pads 120 are formed over the holes. Alternatively, instead of drilling holes completely through the substrate, depressions can be drilled into the substrate and the deposited constantan can be filled into the depressions. In either case, the soldering pads 120 are "peg-fixed" to the substrate by the constantan under the soldering pads. (For the purpose of facilitating the filling of the holes or depressions, a taper can be used to taper the holes or depressions, as described immediately below for the narrow channels and wide channels.)

[0102] Next, in the drilling process 88, typically using laser drilling technology, a plurality of narrow channels and one or more wide channels 44 are drilled into the substrate. (The narrow channels can be seen in FIG. 5, while the wide channels cannot be seen in the same figure.) Typically, the channels are drilled from the inner surface of the substrate using a taper such that the channels become narrower as they approach the outer surface. This facilitates the collection of metal on the walls of the channels during subsequent sputtering processes. Additionally, using the copper trace 114 as a defining portion, blind vias 80 can be drilled (e.g., by laser drilling) through the substrate from the outer surface of the substrate to the portion of the outer surface designated for the sensing electrodes. (In other words, the portion of the substrate disposed on the copper trace can be removed to expose the copper trace.) Typically, a taper is used for the blind vias such that the blind vias become narrower as they approach the inner surface of the substrate. This facilitates the collection of metal on the walls of the blind vias.

[0103] Next, in the first masking step 90, the copper traces and the constantan traces are masked along with the exclusion zones 91 (i.e., the exposed portions of the inner surface of the substrate) designated to insulate these traces. (However, the portion of the constantan trace designated for the thermocouple junction is not masked.) Additional exclusion zones designated to insulate the gold traces that cross the constantan traces (and thus form the constantan-gold thermocouple) are also masked. Additionally, the exclusion zones on the outer surface designated to insulate the sensing electrodes are masked.

[0104] Thereafter, in the deposition step 92, a thin layer of gold 30 is deposited on the inner and outer surfaces of the substrate and also within the channels. The deposition step 92 can be performed by physical vapor deposition (PVD) such as sputtering deposition. (Typically, a seed layer of a base metal such as titanium-tungsten is sputtered onto the substrate prior to the sputtering of gold.) Thanks to the mask, gold is not deposited on the traces or the exclusion zones.

[0105] The deposited gold includes an inner layer 70, an outer layer 50, a plating layer 52, and an initialization layer for the column 48. The deposited gold further includes a gold trace 122 that coats the constantan trace at the thermocouple junction 124. Each gold trace 122 terminates at a respective gold trace soldering pad 126. The deposited gold further includes a respective copper trace soldering pad 116 for each of the copper traces. In some embodiments, the copper trace soldering pad 116 and / or the gold trace soldering pad 126 are fixed to the substrate with pins as already described with respect to the constantan trace soldering pads. The deposited gold further includes at least one gold soldering pad 128 connected to the inner layer 70. The gold soldering pad 128 may also be fixed to the substrate with pins.

[0106] After evaporation, the mask (along with all the gold deposited on the mask) is removed in the mask removal step 93. Subsequently, in the second masking step 94, the traces, the inner surface exclusion zone surrounding the traces, and the entire outer surface of the substrate are masked.

[0107] Following the second masking step 94, with the traces and the outer surface masked, in the first plating step 98, the substrate is plated in a gold plating bath for a first time interval. Plating the substrate fills any gaps in the gold and further increases the thickness of the gold. As a result, for example, while the inner layer 70 reaches a thickness of 5 to 40 micrometers, the diameter of the wide channels decreases to 30 to 200 micrometers. Also, the narrow channels can be completely filled.

[0108] Typically, the plating of the substrate is electrochemical, so that the current flowing through the gold that already coats the substrate attracts gold ions in the plating bath. The amplitude and duration of the current may be controlled so that the gold reaches the desired thickness.

[0109] Following the first plating step 98, in a mask removal step 100, the masks on the inner and outer surfaces of the substrate are removed, except for the aforementioned exclusion zones designated to insulate the sense electrodes. Next, in a coverlay application step 101, at least one coverlay 130 is applied over the traces and over the inner surface exclusion zones. (In some embodiments, as illustrated in the inset of FIG. 5, coverlay 130 is transparent or substantially transparent.)

[0110] Typically, the proximal portion of coverlay 130 covering tab 47 is shaped to define a window 132 that exposes the solder pads, thereby allowing the solder pads to be thickened during subsequent plating processes. (An additional cover 142 having a window aligned with window 132 may cover the proximal portion of the coverlay.) Typically, the solder pads are not completely exposed; rather, they are maintained in a "captured" state by coverlay 130 in that one or more edges of each solder pad are covered by the rim of window 132. Thus, coverlay 130 serves to hold the solder pads against substrate 41 during subsequent soldering processes.

[0111] Subsequently, in the second plating step 102, the substrate is plated in the plating bath over a second time interval, filling any gaps within the outer layer 50 and thickening the inner layer, outer layer, and plating layer. For example, the second plating can decrease the diameter of the wide channels from 15 to 150 micrometers while increasing the thickness of the inner layer from 10 to 50 micrometers. Typically, the final thickness of the inner layer is the same as the thickness of the coverlay to obtain a smooth inner surface. (To avoid any confusion, the term "inner surface" is used herein to refer to the surface formed by the coverlay and the inner gold layer, while the term "inner side surface" is used to refer to the underlying surface of the substrate.) Additionally, if the narrow channels were not completely filled during the first plating step 98, these channels are completely filled during the second plating step 102. Similar to the first plating step 98, the amplitude and duration of the current in the plating bath can be controlled to obtain the desired thickness. (In some embodiments, the outer surface is masked prior to the deposition step 92 so that gold is not deposited on the outer surface during the deposition step 92. In such embodiments, a thin layer of gold is deposited on the outer surface after the mask removal step 100 and prior to the second plating step 102.)

[0112] Following the second plating step 102, in the aperture drilling step 104, the apertures 62 are drilled through the support structure 36. (Instead of drilling, any other suitable technique such as chemical etching may be used to form the apertures.) Next, in the bonding step 106, a suitable adhesive is applied between the support structure 36 and the smooth inner surface formed by the coverlay 130 and the inner layer 70 to align the apertures 62 with the perfusion holes 72 while bonding the support structure to the inner surface. Typically, the area of the apertures is larger than the area of the perfusion holes, and any small misalignment is corrected when bonding the support structure.

[0113] Next, in the deformation step 108, the electrode 40 is deformed into a desired shape. For example, the electrode may be inserted into a forming jig that forms the electrode around a suitable mandrel. After inserting the electrode into the jig, the jig is placed in the furnace. Subsequently, the furnace heats the electrode to a suitable temperature while pressure is applied to the electrode. By the combination of heat and pressure, the electrode is joined to itself in the desired shape.

[0114] Generally, the substrate and the support structure can be deformed into any desired shape. However, typically, during the deformation step 108, the substrate and the support structure are shaped to define an internal lumen. For example, the substrate and the support structure may be shaped to define a single including an internal lumen, as described above with reference to FIGS. 2A and 3. Alternatively, for example, the substrate and the support structure may be shaped to define a ring.

[0115] Typically, to facilitate the manufacture of a single-shaped electrode, the substrate 41 includes two portions continuous with each other, namely, a distal circular portion 41a and a proximal rectangular portion 41b. Similarly, the support structure 36 includes two portions continuous with each other, namely, a distal support portion 36a including a plurality of spokes 134 radially extending from a central hub 136, and a proximal support portion 36b. During the bonding step 106, the distal support portion 36a is bonded to the inner surface of the circular portion 41a, and an adhesive is applied to the outer surface of the spokes 134. (These surfaces are opposite to the surfaces shown in FIG. 5.) In addition, the proximal support portion 36b is bonded to the inner surface of the rectangular portion 41b, but a part of the distal portion of this inner surface remains exposed. The adhesive is applied to the outer surface of the overhanging tab 138 of the proximal support portion 36b, and this overhanging tab 138 overhangs on the side of the rectangular portion 41b. (The proximal support portion 36b may also overhang on the proximal end of the rectangular portion 41b.)

[0116] Subsequently, during the shaping step 108, the distal support portion 36a and the circular portion 41a are folded over the upper portion of the mandrel, while the proximal support portion 36b and the rectangular portion 41b are wound around the mandrel. To maintain this configuration, the outer surface of the spoke 134 is coupled to the exposed distal portion of the inner surface of the rectangular portion 41b, and the outer surface of the tab 138 is coupled to the opposite end of the proximal support portion 36b. (Also, the inner surface of at least one of the spokes may be coupled to the tab 138.) Accordingly, the distal support portion 36a and the circular portion 41a are formed into the dome-shaped portion 40a (see FIG. 2A), while the proximal support portion 36b and the rectangular portion 41b are formed into the cylindrical portion 40b.

[0117] Thereafter, in the soldering step 110, the wire is soldered onto the soldering pads. Specifically, the wire that delivers the RF current from the generator 27 (see FIG. 1) is soldered onto the gold soldering pad 128, while the other wire that delivers a signal to the processor 23 is soldered onto the other soldering pad.

[0118] Finally, in the connecting step 112, the electrode is connected to the catheter. For example, the proximal support portion 36b may be coupled to the base 58 of the flow diverter (see FIG. 3). Alternatively or additionally, as already described with reference to FIG. 3, the protrusion belonging to the base 58 may be snap-fitted into the complementary hole 140 within the proximal support portion 36b. Subsequently, the flow diverter may be connected to the fluid supply tube belonging to the catheter. (Alternatively, the flow diverter may be connected to the fluid supply tube before the electrode is connected to the flow diverter.)

[0119] Certain known ablation catheters are constructed from double-sided flexible circuits, and the external metal of the circuit is used to form the catheter tip electrode used for ablation. However, in these known techniques, the polymer layer between the external metal and the internal metal can cause significant thermal resistance and can serve to sustain an increase in the temperature of the outer surface. One solution to these and other problems is shown in FIGS. 6 - 8. Thereby, the illustrated solution significantly increases heat transfer through the polymer layer (e.g., PCB) through a plurality of thermal vias 80 (e.g., thousands of vias 80) formed in the polymer layer. The vias 80 electrically and thermally join the external metal layer 70 to the internal metal layer 50 of the embodiments described in FIGS. 6 - 8, thereby enabling heat transfer from the outside to the inside such that the temperature of the tip 32 can be cooled by the saline used for perfusion. The vias 80 shown in FIGS. 6 - 8 may typically be solid cylinders of gold or at least some may be plated through vias, allowing the perfusion fluid to move externally.

[0120] Layers 50, 70 are thermally conductive and are particularly effective at transferring heat from the tissue because at least the flow of heat from the central (and hottest) region of the ablation site, when positioned above the hottest part of the tissue, clearly depends on the thermal conductivity of the tip 32. Next, the flow of heat through the catheter tip 32 is increased, including that which goes into the fluid (e.g., perfusion and / or blood) by providing a path for the heat from the tissue. Heat is obtained externally and the outer thermal conductive layer 70 passes a portion of it directly to the blood. A portion of the heat flows through the heat bridge, as described in more detail below. In this regard, the plated perfusion holes described herein transfer some of the heat to the perfusion fluid, and the inner layer 50 can transfer the remaining heat to the perfusion fluid through its surface into the inner layer 50. The perfusion fluid flowing through the plated holes loses some of the heat to the walls of the perfusion holes and most of it to the blood after exiting the catheter tip 32.

[0121] The purpose of the heat conduction layers 50, 70 is to increase the internal heat flow and thus provide the maximum contact area with the cooling fluid flow (e.g., blood, perfusion, etc.). Layers 50, 70 are also effective for efficient heat transfer between layers that increases the contact area. Layers 50, 70 are also effective in mimicking the structure of an all-metal tip, and cooling occurs from all surfaces exposed to the liquid.

[0122] Specifically, FIG. 6 shows a perspective view of an exemplary structural distal tip 32 of the ablation catheter 22 of the present disclosure. As will be described in more detail below, the tip 32 can include a PCB 160 (more specifically shown in FIGS. 7A - B). This is attached to or otherwise formed with the dome-shaped portion 40a and the cylindrical portion 40b. For example, the PCB 160 can be the perfusion holes 72 and the corresponding electrodes of the tip 32 facing the internal tissue of the heart 24, and can be wrapped with the inner layer 70 and the outer layer 50. The configuration of the distal tip 32 shown in FIG. 6 is an exemplary configuration selected for the purpose of assisting conceptual understanding only. In alternative embodiments, any other suitable configuration can also be used.

[0123] FIGS. 7A - 8 show the configuration of an exemplary distal tip 32 of the ablation catheter 22 of the present disclosure. Specifically, FIG. 7A shows an inner perspective view of the distal tip 32 in a cross-section along the center line of the distal tip 32 showing the inner surface of the distal tip 32, and FIG. 8 shows an outer perspective view of the same exemplary tip 32. The tip 32 in the illustrated example includes a cylindrical portion 40b and a dome-shaped portion 40B, and it can be seen that these each include selectively arranged perfusion holes 72 and blind vias 80. Blind vias 80 can be provided for conductivity, so that the inner layer 70 is in direct contact with the outer layer 70, and one exemplary distance between each blind via 80 can be about 0.2 - 0.3 mm. The perfusion holes 72 of the illustrated embodiment can themselves (e.g., walls plated with gold) serve as heat transfer vias.

[0124] Referring now to FIG. 7B, this figure schematically shows an enlarged longitudinal cross-section at C-C through the distal tip 32. As can be seen from the figure, the example shown is a dual metal layer, whereby the inner layer 70 and the outer layer 50 are shown and constructed from metal. What can be sandwiched therebetween can be a PCB 160 having a plurality of selectively positioned vias 80 (e.g., thermal bridges). The inner layer 70 and the outer layer 50 can be constructed from gold and their typical thicknesses can be about 40 micrometers each. The typical diameter of the vias 80 in this embodiment can be about 60 micrometers. The typical thickness of the wall plating of the irrigation holes 72 in this embodiment can be about 25 micrometers. The typical thickness of the PCB layer 160 in this embodiment can be about 50 micrometers. Thus, the total shell thickness of the catheter tip 32 shown in FIG. 7A can be about 130 micrometers (i.e., 0.13 mm).

[0125] Various aspects of the disclosed solutions can be more fully understood from the following description of the implementation of several examples and the corresponding results. Some experimental data are presented herein for illustrative purposes and should not be construed as limiting the scope of the disclosed technology in any way, or as excluding any alternative or additional embodiments.

[0126] A first example of a particular example of the disclosed technology and the corresponding results will now be described with respect to FIG. 9. In FIG. 9, A graphic depiction showing the results obtained from a finite element simulation (COMSOL) is provided This finite element simulation is the phase to compare the capabilities of a PCB-based catheter tip that utilizes interconnected metal layers and a catheter tip portion having no such components of the present invention (hereinafter referred to as "standard flex circuit") and is performed was. The simulation parameters relate to A both the conditions of ablation (e.g., time, ablation current, irrigation, position of the ablation catheter, etc.) and the environment containing blood and tissue having associated thermoelectric properties and geometries Thus, it was generally the same in the example of the standard flex circuit and the example of the double metal layer。The exemplary ablation catheter 22 was set at an angle of 45° to the tissue, and the penetration depth was 0.8 mm, which was considered typical and normal operating conditions. Two scenarios were analyzed, including a first scenario where the ablation current, corresponding to 30 - 40 and up to 30 s, was set between 0 and 0.63 amperes according to the measured impedance. The results of this first scenario are shown in FIGS. 9 and 10. The second scenario included an ablation current, which was set at 0.9 A for a maximum of 5 s, corresponding to 80 - 100 W according to the measured impedance. The safety in both scenarios was evaluated at temperatures exceeding 130°C. The reason is that such temperatures are considered dangerous as there is a high probability that the tissue will rupture due to the accumulation of steam (e.g., steam pop).

[0127] Moving on to FIG. 9 showing the results of the first scenario, the temperature field is shown with a maximum value of about 130° C. for the distal tip of the standard flex circuit. Specifically, the distal tip 32 is positioned on the ablation surface and maintained for about 4.7 seconds with an ablation current of about 0.63 amperes, whereby it can be seen that an ablation width of about 4.6 mm and an ablation depth of about 3.0 mm are reached. FIG. 10 shows a temperature field of up to about 130° C. for the distal tip of an exemplary double metal layer distal tip ablation catheter. Specifically, the distal tip 32 is positioned on the ablation surface and maintained for 30 seconds with an ablation current of about 0.63 amperes, whereby it can be seen that an ablation width of about 8.9 mm and an ablation depth of about 5.6 mm are reached. In other words, compared to the results shown for the distal tip of the standard flex circuit, the distal tip of the double metal layer (e.g., a similar embodiment of the tip 32 shown in FIGS. 7-8) at an ablation current of about 0.63 amperes demonstrated an improvement of about 93.5% in ablation width (i.e., from about 4.6 mm to about 9.6 mm), an improvement of about 86.7% in ablation depth (i.e., from 3 mm to 5.6 mm), and an improvement of about 538.3% in what is considered to be a clinically safe ablation time (i.e., ablation time during the observation of non-safe temperatures from about 4.7 seconds to about 30 seconds). Stated another way, the structure of the catheter tip 32 in FIGS. 7-8 is clearly safer, more effective, more sustainable, and at an ablation current of about 0.63 amperes, imparted a larger ablation site than the tip of the standard flex circuit.

[0128] Moving on to FIG. 11 showing the results of the second scenario, the temperature field is shown with a maximum value of about 130° C. for the distal tip of the standard flex circuit. Specifically, the distal tip 32 of the catheter 22 is positioned on the ablation surface, and the ablation current is maintained at about 0.90 amperes for 1.7 seconds, whereby it can be seen that the damage width reaches 4.3 mm and the damage depth reaches 2.6 mm. FIG. 12 shows the temperature field of up to about 130° C. at the distal tip of an exemplary double metal layer ablation catheter. Specifically, the distal tip 32 is positioned on the ablation surface and maintained for 4.5 seconds with an ablation current of about 0.90 amperes, whereby it can be seen that the damage width reaches about 6.9 mm and the damage depth reaches about 3.6 mm. In other words, when compared with the depicted results of the double metal layer (e.g., similar embodiments of the tip 32 shown in FIGS. 7-8) at an ablation current of about 0.90 amperes in FIG. 11, the tip of the exemplary double metal layer demonstrated an improvement of about 60.5% in damage width (i.e., about 4.3 mm to 6.9 mm), an improvement of about 38.5% in damage depth (i.e., 2.6 mm to 3.6 mm), and an improvement of about 164.7% in what is considered to be a clinically safe ablation time (i.e., ablation time during the observation of unsafe temperatures from about 1.7 s to about 4.5 s). Put another way, the structure of the catheter tip 32 in FIGS. 7-8 is shown to be safer, more effective, more sustainable, and impart a larger ablation site than the standard flex circuit tip at an ablation current of about 0.90 amperes.

[0129] FIG. 13 shows a map of heat flux for a double metal layer constructed of platinum and connected by thermal vias 80 through an exemplary PCB 160. Thereby, the catheter 22 during the simulation was positioned at an angle of about 45° with respect to the tissue and maintained for 30 seconds with an insertion of 1 mm.

[0130] FIG. 14 shows a temperature map of a platinum constructed dual metal layer connected by thermal vias 80 through an exemplary PCB 160. Thereby, the catheter 22 was positioned for vertical insertion (e.g., at an angle of about 90° to the tissue) and maintained for 2.5 seconds.

[0131] FIG. 15 shows a graph summarizing the maximum temperature of tissue during ablation between a standard flex circuit and the distal catheter tip 32 of the dual metal layer. An ablation current of about 0.63 amperes (about 35 W) is shown over an ablation duration of 0 - 30 s at temperatures in the range of about 40 - 220 °C during ablation. It can be seen that the temperature curve of the distal tip of the standard flex circuit reaches a temperature safety limit of 130 °C at about 5 seconds of ablation time. In contrast, the distal catheter tip of the dual metal layer of the present disclosure never reaches a temperature safety limit of 130° even after 30 seconds of ablation time.

[0132] FIG. 16 shows a graph summarizing the maximum temperature of tissue during ablation between the flex and the distal catheter tip 32 of the dual metal layer. An ablation current of 0.9 A (about 90 W equivalent) is shown over an ablation of 0 - 5 s at temperatures in the range of about 40 - 245 °C during ablation. It can be seen that the temperature curve of the distal tip of the standard flex circuit reaches a temperature safety limit of 130° at about 4.5 seconds of ablation time. In contrast, the distal catheter tip of the dual metal layer of the present disclosure reaches a temperature safety limit of 130° after about 1.7 seconds of ablation time.

[0133] FIG. 17 shows a perspective view of the heat generated in a hemisphere of approximately 2 mm radius under an exemplary illustration of the distal tip 32 of the dual metal layer of the catheter 22 of the present disclosure at about 1.5 W. The hemisphere shown is generally around the location where the center of ablation of the distal tip 32 generally exists. Of course, the hemisphere shown is merely representative of one embodiment, and other shaped ablation sites are contemplated along with the ablation radius of the solution of the present disclosure.

[0134] FIG. 18 shows a perspective view of an exemplary embodiment of the distal tip of a dual metal layer of a catheter that contacts tissue. The total heat flux through the surface of the distal tip 32 of FIG. 18 is about -0.82 W, while the standard flex circuit tip of the present disclosure is about -0.3 W. Thus, from the original 1.5 W, the distal tip of the dual metal layer retained 0.7 W, whereas in the case of the standard flex circuit, it retained 1.2 W, which is an increase of about 71.5%. Other cases (e.g., a single metal layer) were shown to fall between the extremes. Although the above greatly simplifies the various features and systems, it is relatively clear that without an efficient cooling method in the hotter regions of the distal tip 32, the ablation site would produce a temperature high enough to prevent the formation of damage that exceeds a certain size within the safety limits.

[0135] FIG. 19 is a flowchart relating to method 1900 according to some embodiments of the present disclosure. Step 1910 includes inserting the distal end of a catheter into the interior of a subject's body, the distal end including an outer layer of thermally conductive metal, an inner layer of thermally conductive metal, a polymer layer between the inner and outer layers, and a plurality of heat bridges selectively disposed through the polymer layer between the inner and outer layers, thereby significantly increasing the heat transfer of the catheter tip through the polymer layer. Step 1920 includes passing an ablation current through the outer layer to the tissue while in contact with the tissue to generate heat within the tissue and transfer it through the heat bridges to the inner thermally conductive layer. Step 1930 includes contacting the subject's tissue with the outer layer following insertion of the distal end of the catheter into the interior of the subject's body. Step 1940 includes discharging heat from the inner thermally conductive layer into the subject's blood, which is by discharging a perfusion fluid by passing it through a plurality of perfusion channels through the inner layer, the outer layer, and the polymer layer.

[0136] FIG. 20 is a flowchart of a method 2000 for manufacturing a catheter tip electrode according to some embodiments of the present disclosure. Step 2010 includes perforating a plurality of thermal bridges through a flexible thermally insulating polymer substrate. Step 2020 includes sandwiching a flexible thermally insulating polymer substrate between an inner surface and an outer surface using a thermally conductive metal. It is understood that in the examples disclosed herein, any thermally conductive material including diamond can be used. The catheter tip electrode may also be a separate thin (e.g., about 1 micrometer) metal layer deposited on the thermally conductive layer.

[0137] Instead of, or in addition to, the traces described above, any other suitable electrical or electronic components may be deposited on the inner surface of the substrate. Such components may include a thermistor for measuring the temperature of tissue, a pressure sensor for measuring the pressure applied to the distal end of the catheter, and / or an electromagnetic sensor for navigating the catheter. These components (along with suitable surrounding exclusion zones) may be masked or coated whenever masking or coating is required, as already described for the traces.

[0138] Note that the scope of the present disclosure includes any suitable modifications made to method 82 with respect to the order of steps performed and / or the various materials used, as will be apparent to those skilled in the art. For example, any suitable thermally conductive metal can be used instead of copper, gold, or constantan.

[0139] In general, the embodiments described herein can be combined with any of the embodiments described in U.S. Patent Application Publication No. 2018 / 0110562 or U.S. Patent Application No. 15 / 793126, the respective disclosures of which are incorporated herein by reference.

[0140] It will be understood by those skilled in the art that the present disclosure is not limited to what is specifically shown and described herein. Rather, the scope of the embodiments of the present disclosure includes both various combinations and sub - combinations of the features described herein, as well as variations and modifications of features that do not exist in the prior art and that would be apparent to those skilled in the art upon a reading of the above description. Documents incorporated by reference into this patent application are considered to be a part of this application, except that if any term is defined in these incorporated documents in a manner that conflicts with the definition explicitly or implicitly made herein, only the definition herein shall be considered.

[0141] 〔Embodiment〕 (1) An electrophysiological catheter tip for use in ablation, comprising an outer layer of a conductive and thermally conductive metal, an inner layer of a conductive and thermally conductive metal, a polymer layer between the inner layer and the outer layer, and a plurality of thermal bridges selectively disposed through the polymer layer between the inner layer and the outer layer, wherein when about 0.63 amperes is delivered to the tip of the outer layer, at least about 100% improvement in clinically safe ablation time is achieved compared to a standard flexible circuit ablation catheter with about 0.63 amperes, and when about 0.90 amperes is delivered to the outer layer of the tip, at least about 100% improvement in clinically safe ablation time is achieved compared to a standard flexible circuit ablation catheter having an ablation current of about 0.90 amperes, such that the heat transfer at the tip of the catheter through the polymer layer is increased. The electrophysiological catheter tip. (2) The catheter tip according to embodiment 1, wherein the plurality of thermal bridges includes at least 1000 thermal bridges. (3) The catheter tip according to Embodiment 1, wherein the heat bridge electrically and thermally joins the inner layer and the outer layer, thereby enabling heat transfer from the outside to the inside of the catheter tip, and the temperature can be cooled by the physiological saline used during perfusion. (4) The heat bridge includes a solid cylinder, enabling the perfusion fluid to transfer heat to the outside. The catheter tip according to Embodiment 1, wherein the diameter of the heat bridge is about 60 micrometers. (5) The catheter tip according to Embodiment 1, wherein the distance between the heat bridges is about 0.2 - 0.3 mm.

[0142] (6) A plurality of electrodes oriented to contact heart tissue, and a plurality of metal perfusion holes disposed between the inner layer and the outer layer. The catheter tip according to Embodiment 1 further comprises the above. (7) The catheter tip according to Embodiment 6, wherein the thickness of the wall plating in the perfusion hole is about 25 micrometers. (8) The catheter tip according to Embodiment 6, wherein the outer layer includes an overall shell thickness of about 130 micrometers. (9) The catheter tip according to Embodiment 6, wherein the catheter tip is configured to generate a hemispherical ablation site generated by heat with a radius of at least about 2 mm. (10) A cylindrical section, and a distal dome section of the cylindrical section. The bridge is a heat bridge disposed within the cylindrical section and the dome section. The catheter tip according to Embodiment 6 further comprises the above.

[0143] (11) Further comprising a catheter configured to be inserted into a target body, wherein the support structure is connected to a distal end of the catheter, and the distal end of the catheter comprises a flow diverter configured to bypass fluid received from a proximal end of the catheter, and the support structure is connected to the flow diverter such that the flow diverter is disposed inside the internal lumen, the catheter tip according to Embodiment 1. (12) A method comprising: inserting a distal end of a catheter into a target body, wherein the distal end comprises an electrical and thermal outer layer, a conductive and thermally conductive inner layer, a polymer layer between the inner layer and the outer layer, and a plurality of heat bridges selectively disposed through the polymer layer between the inner layer and the outer layer, thereby significantly increasing the heat transfer of the catheter tip through the polymer layer, subsequent to inserting the distal end of the catheter into the target body, contacting the tissue of the target with the outer layer, while in contact with the tissue, passing an ablation current through the outer layer to the tissue to generate heat in the tissue and transmit the heat through the heat bridge to the inner thermally conductive layer, and discharging the heat from the inner thermally conductive layer into the blood of the target by passing a perfusion fluid through a plurality of perfusion channels through the inner layer, the outer layer, and the polymer layer. (13) Orienting the distal end of the catheter at an angle of either 45° or 90° with respect to the tissue, penetrating the tissue to a penetration depth, and ablating the tissue with the ablation current for a predetermined duration at a predetermined safe temperature through the distal end of the catheter, the method according to Embodiment 12. (14) The method according to Embodiment 13, wherein the penetration depth is about 0.8 mm. (15) The method according to embodiment 13, wherein the step of ablating the tissue results in a damage depth of about 5.6 mm at an ablation current of about 0.63 amperes.

[0144] (16) The method according to embodiment 13, wherein the step of ablating the tissue results in a damage width of about 8.9 mm at an ablation current of about 0.63 amperes. (17) The method according to embodiment 13, wherein the predetermined duration is at least about 30 seconds, the ablation current is about 0.63 amperes, and the catheter maintains the ablation site at about 130° C. or less throughout the ablation, thereby avoiding tissue rupture. (18) The method according to embodiment 13, wherein the step of ablating the tissue provides at least about a 93% improvement in damage width for a standard flexible circuit ablation catheter having an ablation current of about 0.63 amperes. (19) The method according to embodiment 13, wherein the step of ablating the tissue provides at least about a 500% improvement at a clinically safe ablation time for a standard flexible circuit ablation catheter having an ablation current of about 0.63 amperes. (20) The method according to embodiment 13, wherein the step of ablating the tissue provides at least about an 85% improvement in damage depth for a standard flexible circuit ablation catheter having an ablation current of about 0.63 amperes.

[0145] (21) The method according to embodiment 13, wherein the predetermined duration is at least about 5 seconds, the ablation current is about 0.90 amperes, and the catheter maintains the ablation site at about 130° C. or less throughout the ablation, thereby avoiding tissue rupture. (22) The method according to embodiment 13, wherein the step of ablating the tissue provides at least about a 60% improvement in damage width for a standard flexible circuit ablation catheter having an ablation current of about 0.90 amperes. (23) The step of ablating tissue is the method according to Embodiment 13, which provides at least about 160% improvement in clinically safe ablation time for a standard flexible circuit ablation catheter with an ablation current of about 0.90 amperes. (24) The step of ablating tissue is the method according to Embodiment 13, which provides at least about 38% improvement in damage depth for a standard flexible circuit ablation catheter with an ablation current of about 0.90 amperes. (25) The step of ablating tissue is the method according to Embodiment 13, which provides a damage depth of about 3.6 mm at an ablation current of about 0.90 amperes.

[0146] (26) The step of ablating tissue is the method according to Embodiment 13, which provides a damage width of about 6.9 mm at an ablation current of about 0.90 amperes. (27) A method comprising: perforating a plurality of thermal bridges through a flexible thermally insulating polymer substrate; using a thermally conductive metal to sandwich the flexible thermally insulating polymer substrate between an inner surface and an outer surface. (28) The method according to Embodiment 27, further comprising perforating a plurality of perfusion holes through the inner layer, the outer layer, and the thermally insulating polymer substrate, wherein the perfusion holes have a diameter larger than that of the thermal bridges. (29) The method according to Embodiment 27, further comprising joining the thermally conductive metal covering the inner layer to a support structure of an ablation catheter; and shaping the substrate and the support structure to define an internal lumen. (30) Shaping the substrate and the support structure shapes the substrate and the support structure to define a single including the internal lumen; The method according to embodiment 29, comprising connecting the support structure to a distal end of a catheter configured to be inserted into a target body interior.

Claims

1. An electrophysiological catheter tip for use in ablation, comprising: an outer layer of a conductive and thermally conductive metal; an inner layer of a conductive and thermally conductive metal; a polymer layer between the inner layer and the outer layer, the polymer layer being a printed circuit board PCB comprising copper traces and constantan traces; a plurality of perfusion holes disposed through the polymer layer between the inner layer and the outer layer, providing a fluid passage and including a plated layer of a conductive and thermally conductive metal, the plated layer connecting the outer layer to the inner layer; a plurality of thermal bridges selectively disposed through the polymer layer between the inner layer and the outer layer; and comprising; the plurality of thermal bridges being filled with a channel passing between the outer surface and the inner surface of the polymer layer and including a solid cylinder of a thermally conductive metal connecting the outer layer to the inner layer, the thermally conductive metal of the solid cylinder being selected from gold, palladium, or platinum, the plurality of thermal bridges increasing heat transfer of the catheter tip through the polymer layer.

2. The catheter tip according to claim 1, wherein the plurality of thermal bridges includes at least 1000 of the thermal bridges.

3. The catheter tip according to claim 1, wherein the thermal bridges electrically and thermally join the inner layer and the outer layer, thereby enabling heat transfer from the outside to the inside of the catheter tip and the temperature being coolable by the physiological saline used during perfusion.

4. The catheter tip according to claim 1, wherein each of the plurality of thermal bridges has a diameter of 60 micrometers.

5. The catheter tip according to claim 1, wherein the distance between the thermal bridges is 0.2 to 0.3 mm.

6. The catheter tip according to claim 1, further comprising a plurality of electrodes oriented to contact heart tissue.

7. The catheter tip according to claim 6, wherein the thickness of the plated layer in the perfusion hole is 25 micrometers.

8. The catheter tip according to claim 6, wherein the total thickness of the outer layer, the inner layer, and the polymer layer is 130 micrometers.

9. The catheter tip according to claim 6, wherein the catheter tip is configured to generate a hemispherical ablation site generated by heat with a radius of at least 2 mm.

10. A cylindrical section, And a distal dome section of the cylindrical section, and further comprising: The catheter tip according to claim 6, wherein the plurality of heat bridges are disposed in the cylindrical section and the dome section.

11. Further comprising an internal lumen, The catheter tip is connected to the distal end of a catheter configured to be inserted into a subject's body, and the distal end of the catheter is provided with a flow diverter configured to bypass fluid received from the proximal end of the catheter. The catheter tip is connected to the flow diverter such that the flow diverter is disposed inside the internal lumen. The catheter tip according to claim 1.

12. A method comprising: Manufacturing an electrophysiological catheter tip for use in ablation, Drilling a plurality of channels for heat bridges through a flexible thermally insulating polymer substrate having a thickness of 50 micrometers, wherein each of the plurality of channels has a diameter of 60 micrometers, and the flexible thermally insulating polymer substrate is a printed circuit board (PCB) comprising copper traces and constantan traces; Drilling a plurality of irrigation holes through the flexible thermally insulating polymer substrate to provide fluid passageways; Forming an inner layer and an outer layer, a solid cylinder filling each of the plurality of channels, and a plating layer for the irrigation holes using a thermally conductive metal, thereby sandwiching the flexible thermally insulating polymer substrate between the inner layer and the outer layer, wherein the inner layer and the outer layer each have a thickness of 40 micrometers, and the solid cylinder and the plating layer each connect the outer layer to the inner layer; Including manufacturing; Testing the catheter tip using finite element simulation, Setting the catheter tip at an angle of 45° and a penetration depth of 0.8 mm with respect to tissue, Maintaining ablation for 30 seconds with an ablation current of 0.63 amperes, and / or Maintaining ablation for 4.5 seconds with an ablation current of 0.90 amperes, Testing, including, a method.

13. The method according to claim 12, wherein the perfusion hole has a diameter larger than that of the channel.

14. Manufacturing the catheter tip includes joining the thermally conductive metal covering the inner layer to a support structure of the ablation catheter, further including shaping the thermally insulating polymer substrate and the support structure to define an internal lumen, the method according to claim 12.

15. Shaping the thermally insulating polymer substrate and the support structure is to shape the thermally insulating polymer substrate and the support structure into a single shape including the internal lumen, the single shape including a dome-shaped portion and a cylindrical portion extending from the dome-shaped portion, and connecting the support structure to a catheter distal end configured to be inserted into the body of a subject, the method according to claim 14.

16. The outer layer has a thickness of 40 micrometers, The inner layer has a thickness of 40 micrometers, The polymer layer has a thickness of 50 micrometers, The diameter of each of the plurality of heat bridges is 60 micrometers, the catheter tip according to claim 1.

17. The electrically and thermally conductive metal of the outer layer and the electrically and thermally conductive metal of the inner layer are each selected from gold, palladium, or platinum, the catheter tip according to claim 16.

18. The electrically and thermally conductive metal of the outer layer, the electrically and thermally conductive metal of the inner layer, and the thermally conductive metal of the solid cylinder are gold, the catheter tip according to claim 17.

19. The thermally conductive metal is gold, the method according to claim 12.

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