Improving Heat Transfer through the Tip of a Catheter

Abstract

The present invention is titled "Improved Heat Transfer through the Catheter Tip". Embodiments described in this disclosure include: a catheter tip that includes 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 thermal bridges selectively positioned between the inner and outer layers and passing through the polymer layer, thereby significantly increasing heat transfer through the polymer layer at the catheter tip. Other embodiments are also described.

Description

Technical Field

[0001] The present disclosure relates to ablation catheters and their 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 delivered from the electrode into the tissue. The RF energy raises the temperature of the tissue, thereby creating an ablation lesion in the tissue.

[0003] U.S. Patent Application Publication 2018 / 0110562, the disclosure of which is incorporated herein by reference, describes a catheter that includes 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 connected to the electrical interconnects. Summary of the Invention

[0004] According to some embodiments of the present disclosure, there is provided an electrophysiology catheter tip that includes a flexible adiabatic substrate; the flexible adiabatic substrate includes an inner surface and an outer surface and is shaped to define (i) a plurality of narrower channels between the inner surface and the outer surface and (ii) one or more wider channels between the inner surface and the outer surface. The tip further includes: an outer layer of a conductive and thermally conductive metal that covers at least a portion of the outer surface; an inner layer of a conductive and thermally conductive metal that covers at least a portion of the inner surface; a plating layer of a conductive and thermally conductive metal that plates the wider channels to connect the outer layer to the inner layer; and corresponding columns of a thermally conductive metal that fill the narrower channels to connect the outer layer to the inner layer.

[0005] In some embodiments, the substrate is shaped to define at least 1,000 narrower channels.

[0006] In some embodiments, the total area of the respective outer openings of the narrower 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:

[0009] at least one constantan trace disposed on the inner surface and electrically isolated from the inner layer; and

[0010] at least one gold trace disposed on the inner surface, electrically isolated from the inner layer, and covering the constantan trace at a thermocouple junction.

[0011] In some embodiments, the distal end further includes a support structure bonded to the inner layer, and the substrate and the support structure are shaped to define a lumen.

[0012] In some embodiments, the substrate and the support structure are shaped to define a cannula including a lumen.

[0013] In some embodiments, the distal end further includes a catheter configured to be inserted into a subject's body, and the support structure is coupled to the distal end of the catheter.

[0014] In some embodiments, the distal end of the catheter includes a deflecting element configured to deflect fluid received from the proximal end of the catheter, and the support structure is coupled to the deflecting element such that the deflecting element is disposed inside the lumen.

[0015] In some embodiments, the average diameter of each of the narrower channels is between 5 micrometers and 50 micrometers.

[0016] In some embodiments, the average narrower-channel diameter of each of the narrower channels is less than 50% of the average wider-channel diameter of each of the wider channels.

[0017] In some embodiments, the thickness of the substrate is between 5 micrometers and 75 micrometers.

[0018] In some embodiments, the device further includes one or more conductive traces disposed on the inner surface and electrically isolated from the inner layer, the substrate is shaped to define corresponding holes opposite the traces, and the outer layer includes a main portion; and one or more islands that are electrically isolated from the main portion and contact the traces by at least partially filling the holes.

[0019] In some examples, there is provided an electrophysiology catheter distal end including: a bimetallic layer electrically insulating and thermally insulating substrate including an outer layer of thermally conductive metal; an inner layer of thermally conductive metal; a polymer layer between the inner layer and the outer layer; and a plurality of thermal bridges selectively positioned between the inner layer and the outer layer and passing through the polymer layer, the plurality of thermal bridges increasing heat transfer through the polymer layer of the catheter distal end such that when delivering approximately 0.63 amperes to the outer layer distal end, there is achieved at least approximately a 100% increase in ablation time believed to be clinically safe compared to a standard flexible circuit ablation catheter having approximately 0.63 amperes, and when delivering approximately 0.90 amperes to the outer layer of the distal end, there is achieved at least approximately a 100% increase in ablation time believed to be clinically safe relative to a standard flexible circuit ablation catheter having an ablation current of approximately 0.90 amperes.

[0020] In some embodiments, the catheter distal end includes at least 1000 thermal bridges.

[0021] In some embodiments, the thermal bridge thermally joins the inner and outer layers, allowing heat transfer from the outside to the inside of the catheter tip, and the temperature can be cooled by the saline used during flushing.

[0022] In some embodiments, the thermal bridge includes a solid cylinder, allowing the flushing liquid to transfer heat to the outside (e.g., plated flushing holes that transfer heat both between the layers and to the liquid).

[0023] In some embodiments, the diameter of the thermal bridge is about 60 microns.

[0024] In some embodiments, the distance between the bridges is about 0.2 mm to 0.3 mm.

[0025] In some embodiments, the thermally conductive metals of the inner and outer layers are the same material.

[0026] In some embodiments, the thermally conductive metals of the inner and outer layers are different materials.

[0027] In some embodiments, the thermally conductive metals of the inner and outer layers are gold and have a thickness of about 40 microns.

[0028] In some embodiments, the polymer layer is a printed circuit board (PCB) having a thickness of about 50 microns.

[0029] In some embodiments, the catheter tip is the distal tip of an ablation catheter and further includes a plurality of electrodes oriented to contact cardiac tissue; and a plurality of flushing holes between the inner and outer layers.

[0030] In some embodiments, the flushing holes include walls plated with a heat transfer metal.

[0031] In some embodiments, the thickness of the wall plating in the flushing holes is about 25 microns.

[0032] In some embodiments, the catheter tip has a total outer shell thickness of about 130 microns.

[0033] In some embodiments, the catheter tip is configured to generate a hemispherical ablation zone with a heat generation radius of at least about 2 mm.

[0034] In some embodiments, it includes a cylindrical segment; and a dome segment located distally of the cylindrical segment, wherein the thermal bridge is positioned in the cylindrical segment and the dome segment.

[0035] According to some embodiments of the present disclosure, a method is also provided that includes inserting a distal end of a catheter into a subject's body, the distal end of the catheter including a substrate having an inner surface and an outer surface, the inner surface being at least partially covered by an inner heat-conducting layer and the outer surface being at least partially covered by an outer heat-conducting layer, the substrate being shaped to define: (i) a plurality of narrower channels passing between the inner surface and the outer surface and filled with heat-conducting posts; and (ii) one or more thermally plated wider channels passing between the inner surface and the outer surface. The method further includes, after inserting the distal end of the catheter into the subject's body, bringing the subject's tissue into contact with the outer heat-conducting layer. The method further includes, while in contact with the tissue, passing an electric current through the outer heat-conducting layer (which can be as low as 1 micron as long as it covers a thicker heat-conducting layer) into the tissue such that heat is generated in the tissue.

[0036] The method can provide an inner layer and / or an outer layer, as well as connection bridges and thermally plated flushing channels to act as a single heat-conducting structure such that heat can conduct from the tissue to the structure and be convectively dissipated by the flushing fluid and blood in contact with the structure. In this example, since heat mainly transfers from the central part of the ablation, this reduces the hot spot temperature without adversely affecting the extent of the thermal ablation lesion in the tissue.

[0037] In some embodiments, the tissue includes the subject's heart tissue.

[0038] In some embodiments, the outer end layer includes a main portion and one or more islands electrically isolated from the main portion, and the method further includes using the ten islands to sense electrogram signals from the heart tissue.

[0039] According to some embodiments of the present disclosure, a method is also provided that includes drilling a plurality of narrower channels and one or more wider channels through a flexible adiabatic substrate such that the narrower channels and the wider channels pass between an inner surface of the substrate and an outer surface of the substrate. The method further includes using a heat-conducting material to at least partially cover the inner surface and the outer surface, completely fill the narrower channels, and plate the wider channels.

[0040] In some embodiments, the method includes at least partially covering an inner surface and an outer surface, completely filling a narrower channel, and plating a wider channel, which includes at least partially covering the inner surface and the outer surface, completely filling the narrower channel, and plating the wider channel by depositing a thermally conductive material onto the inner surface and the outer surface of the substrate and into the narrower and wider channels; after depositing the thermally conductive material onto the inner surface of the substrate, plating the substrate for a first time interval in a plating bath of a conductive material while covering the outer surface of the substrate; after plating the substrate for the first time interval, 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 for a second time interval in the plating bath.

[0041] In some embodiments, the method further includes bonding the thermally conductive material covering the inner surface to a support structure; and shaping the substrate and the support structure to define an inner cavity.

[0042] In some embodiments, shaping the substrate and the support structure includes shaping the substrate and the support structure to define a sleeve containing the inner cavity.

[0043] In some embodiments, the method further includes etching one or more conductive traces onto the inner surface of the substrate, depositing the thermally conductive material onto the inner surface of the substrate includes depositing the thermally conductive material onto the inner surface of the substrate such that the conductive traces remain electrically isolated from the thermally conductive material, the method further includes forming holes in the substrate opposite the traces respectively, and depositing the thermally conductive material onto the outer surface of the substrate includes depositing the thermally conductive material onto the outer surface of the substrate to form (i) a main portion, and (ii) one or more islands that are electrically isolated from the main portion and in contact with the traces due to at least partially filling the holes.

[0044] According to some embodiments of the present disclosure, a method is also provided, the method 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 thermal bridges selectively positioned between the inner layer and the outer layer and passing through the polymer layer, thereby significantly increasing heat transfer through the polymer layer at the distal end of the catheter; after inserting the distal end of the catheter into the subject's body, bringing the subject's tissue into contact with the outer layer; while in contact with the tissue, passing an ablation current through the outer layer into the tissue. A portion of the heat generated in the tissue is transferred via the thermally conductive structure of the two layers (inner layer and outer layer) connected by the thermal bridges to the thermal bridge heat conducting layer, and is finally convectively removed from the distal end by the flushing fluid and blood.

[0045] 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 for a predetermined duration with an ablation current / power through the distal end of the catheter under predetermined safe temperature conditions.

[0046] In some embodiments, the penetration depth of the catheter tip is about 0.8 mm.

[0047] In some embodiments, at an ablation current of about 0.63 amperes, the step of ablating the tissue results in an ablation lesion depth of about 5.6 mm.

[0048] In some embodiments, at an ablation current of about 0.63 amperes, the step of ablating the tissue results in an ablation lesion width of about 8.9 mm.

[0049] In some embodiments, the predetermined safe temperature is less than or equal to about 130 °C.

[0050] In some embodiments, the predetermined duration is at least about 30 s and the ablation current is about 0.63 amperes, whereby throughout the ablation process, the catheter maintains the ablation zone at less than or equal to about 130 °C, thereby avoiding tissue rupture.

[0051] In some embodiments, relative to a standard flexible circuit ablation catheter in which the ablation current is about 0.63 amperes, the step of ablating the tissue results in an increase in ablation lesion width of at least about 93%.

[0052] In some embodiments, relative to a standard flexible circuit ablation catheter in which the ablation current is about 0.63 amperes, the step of ablating the tissue results in an increase in ablation time believed to be clinically safe of at least about 500%.

[0053] In some embodiments, relative to a standard flexible circuit ablation catheter in which the ablation current is about 0.63 amperes, the step of ablating the tissue results in an increase in ablation lesion depth of at least about 85%.

[0054] In some embodiments, the predetermined duration is at least about 5 s and the ablation current is about 0.90 amperes, whereby throughout the ablation process, the catheter maintains the ablation zone at less than or equal to about 130 °C, thereby avoiding tissue rupture.

[0055] In some embodiments, relative to a standard flexible circuit ablation catheter in which the ablation current is about 0.90 amperes, the step of ablating the tissue results in an increase in ablation lesion width of at least about 60%.

[0056] In some embodiments, relative to a standard flexible circuit ablation catheter in which the ablation current is about 0.90 amperes, the step of ablating tissue results in an increase in ablation time of at least about 160% believed to be clinically safe.

[0057] In some embodiments, relative to a standard flexible circuit ablation catheter in which the ablation current is about 0.90 amperes, the step of ablating tissue results in an increase in ablation lesion depth of at least about 38%.

[0058] In some embodiments, at an ablation current of about 0.90 amperes, the step of ablating tissue results in an ablation lesion depth of about 3.6 mm.

[0059] In some embodiments, at an ablation current of about 0.90 amperes, the step of ablating tissue results in an ablation lesion width of about 6.9 mm.

[0060] According to some embodiments of the present disclosure, there is also provided a method that includes drilling a plurality of thermal bridges through a flexible adiabatic polymer substrate; and sandwiching the flexible adiabatic polymer substrate between an inner surface and an outer surface using a thermally conductive metal.

[0061] In some embodiments, the step of drilling the thermal bridges includes drilling at least 1,000 thermal bridges.

[0062] In some embodiments, the method further includes drilling a plurality of flushing holes through the inner layer, the outer layer, and the adiabatic polymer substrate, the flushing holes having a diameter greater than that of the thermal bridges.

[0063] The present invention will be more fully understood from the following detailed description of embodiments of the present disclosure in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 A schematic diagram of a system for ablating tissue of a subject according to some embodiments of the present disclosure;

[0065] Figure 2A A schematic diagram of the distal end of a catheter according to some embodiments of the present disclosure;

[0066] Figure 2B A cross-section schematically showing a portion of the distal end electrode of a catheter according to some embodiments 10 of the present disclosure;

[0067] Figure 3 Schematically showing passing through according to some embodiments of the present disclosure Figure 2A The longitudinal section of the distal end shown in;

[0068] Figure 4 A flowchart of a method for manufacturing a distal end electrode of a catheter according to some embodiments of the present disclosure;

[0069] Figure 5 Schematic diagram of the catheter tip electrode before its deformation according to some embodiments of the present disclosure;

[0070] Figure 6 Schematic diagram of the distal end of a catheter according to some embodiments of the present disclosure;

[0071] Figure 7A Schematic diagram of the distal end of a catheter according to some embodiments of the present disclosure;

[0072] Figure 7B Schematically shows a cross-section through a portion of the catheter tip electrode according to some embodiments of the present disclosure;

[0073] Figure 8 Schematic diagram of the distal end of a catheter according to some embodiments of the present disclosure;

[0074] Figure 9 Shows a temperature field of up to about 130 °C in the case of a standard flexible circuit;

[0075] Figure 10 Shows a temperature field of up to about 130 °C in the case of a bimetallic layer;

[0076] Figure 11 Shows a temperature field of up to about 130 °C in the case of a standard flexible circuit;

[0077] Figure 12 Shows a temperature field of up to about 130 °C in the case of a bimetallic layer;

[0078] Figure 13 Shows a heat flux map of the distal end of the present disclosure, which has a bimetallic layer and is constructed of platinum and is connected through vias in an exemplary printed circuit board;

[0079] Figure 14 Shows a temperature map in the case of a bimetallic layer and is constructed of platinum and is connected through heat dissipation holes in an exemplary printed circuit board;

[0080] Figure 15 Shows a graph summarizing the maximum temperature in tissue during ablation between a standard flexible circuit and a bimetallic layer distal catheter tip;

[0081] Figure 16 Shows a graph summarizing the maximum temperature in tissue during ablation between a standard flexible circuit and a bimetallic layer distal catheter tip;

[0082] Figure 17 Shows a perspective view of the heat generated in a hemisphere under an exemplary embodiment of the bimetallic layer distal end of the catheter;

[0083] Figure 18 A perspective view showing an exemplary embodiment of the distal end of a bimetallic layer of a catheter in contact with tissue;

[0084] Figure 19 Is a flow chart of a method according to some embodiments of the present disclosure; and

[0085] Figure 20 Is a flow chart of a method for manufacturing a catheter tip electrode according to some embodiments of the present disclosure. Detailed Description

[0086] Overview

[0087] Embodiments of the present disclosure include an ablation electrode that includes at least one flexible printed circuit board (PCB) bonded to a support metal plate by an adhesive. The flexible PCB includes a flexible adiabatic substrate that includes an outer surface and an inner surface, the outer surface being coated with an outer layer of a conductive (and biocompatible) metal such as gold, palladium, or platinum, and the inner surface being coated with an inner layer of the same (and / or another) thermally conductive metal. The inner surface may further support one or more electronic components electrically isolated from the inner thermal layer, such as sensors (e.g., thermocouples) and traces. After depositing the electronic components, coating the substrate, and bonding the PCB to the support plate, the flexible PCB (along with the support plate) can be deformed into any suitable shape. For example, in some embodiments, the flexible PCB is deformed into a sleeve-shaped electrode, hereinafter referred to as the "tip electrode". The electrode is then coupled to the distal end of a catheter.

[0088] During an ablation procedure, the outer thermal layer is brought into contact with the tissue to be ablated, and then ablation current is passed through the outer thermal layer into the tissue. When ablation current is applied to the tissue, the sensor can obtain any relevant physiological readings from the tissue. Typically, the plated through-holes through the electrode provide an electrical connection between the inner thermal layer and the outer thermal layer such that ablation current can pass outwards through the plated through-holes, and electrogram signals from the tissue can pass inwards through the plated through-holes. The electrical connection can also be provided by blind holes, each such through-hole being formed by removing a portion of the substrate such that the outer thermal layer directly contacts the underlying trace.

[0089] The above-described plated through-holes also provide fluid communication between the inner and outer surfaces of the electrode such that a flushing fluid (e.g., saline) can pass through the plated through-holes into the surrounding blood. The flushing fluid dissipates heat from inside the electrode into the blood, and additionally dilutes the blood at the tissue-electrode interface, thereby reducing the likelihood of coagulation or carbonization. Given the fact that the plated through-holes provide a passage for the flushing fluid, the plated through-holes may also be referred to as "flushing channels" or "flushing holes".

[0090] When using electrodes of the above type, the challenge is that the substrate can provide significant thermal resistance, limiting the amount of heat transferred from the tissue-electrode interface into the electrode. This in turn limits the amount of heat that can be removed by the flushing fluid.

[0091] To address this challenge, the embodiments described herein provide a large number (e.g., tens of thousands) of small closed through-holes (hereinafter referred to as "heat dissipation holes") that enhance the thermal connectivity between the two surfaces of the electrode. Such heat dissipation holes can include, for example, columns of a thermally conductive metal (such as gold) that connect the outer thermally conductive layer to the inner thermally conductive layer. Generally, the heat dissipation holes are distributed across the entire surface of the electrode. The heat dissipation holes increase the amount of heat transferred into the electrode, facilitating the removal of heat by the flushing fluid.

[0092] Embodiments of the present disclosure also include a method of manufacturing the electrode. Generally, both surfaces of the substrate are initially coated with copper; thus, the manufacture of the electrode typically begins by etching away the copper at locations other than those where copper traces are to be formed on the inner surface of the substrate. Next, constantan traces to be used for the thermocouple are deposited on the inner surface. Subsequently, one or more wide channels, a large number of relatively narrow channels, and optionally one or more blind holes are drilled through the substrate.

[0093] Subsequently, a mask is applied to the traces and the surrounding isolation regions on the inner surface of the substrate that will isolate the traces from the inner thermally conductive layer. (The portion of the constantan trace designated as the thermocouple junction is not masked.) Similarly, on the outer surface, another mask is applied to the isolation region that will isolate the microelectrode "islands" from the rest of the outer thermally conductive layer.

[0094] Next, a thin metal (usually gold) layer is sputtered into the channels and onto both surfaces of the substrate. The metal sputtered onto the inner surface includes traces that intersect the constantan traces to form the thermocouple junctions. After sputtering the metal, the mask is removed, leaving the internal traces and isolation regions covered by another mask, and also leaving the entire outer surface covered by a mask.

[0095] Subsequently, the substrate is placed in a plating bath and held for a period of time such that (i) any remaining exposed portions of the inner surface of the substrate are covered by metal, i.e., the metal layer spreads laterally on the inner surface, (ii) the thickness of the inner layer increases, (iii) the narrow channels close to become heat dissipation holes, and (iv) the wide channels narrow to become plated flushing channels. Then the masks on the inner and outer surfaces are removed. Next, the internal traces and isolation regions are covered with at least one surface protection layer.

[0096] Subsequently, the substrate is placed back into the plating bath for another period of time such that the thicknesses of both the outer layer and the inner layer increase and the plated flushing channels narrow. Typically, the total duration that the substrate is held in the plating bath is set such that the thickness of the inner layer reaches the thickness of the table protection layer. (Typically, the thickness of the outer layer does not increase significantly in order to reduce the risk of rupture of the outer layer when the substrate is folded into its final shape.)

[0097] Next, openings having a diameter greater than or equal to the flushing holes are drilled through a support metal plate (including, for example, cobalt-chromium alloy). The support plate is then bonded to the inner heat-conducting layer and the table protection layer such that the openings in the support plate are aligned with the flushing channels in the substrate. Subsequently, the plated substrate and the support plate are deformed into their desired shapes. Finally, the relevant wires are connected to the electrodes, and then the electrodes are coupled to the catheter.

[0098] System Description

[0099] First refer to Figure 1 , which is a schematic diagram of a system 2 for ablating tissue of a subject 26 according to some embodiments of the present disclosure.

[0100] Figure 1 Depicted is a physician 28 performing a monopolar ablation procedure on a subject 26 using an ablation catheter 22. In this procedure, the physician 28 first inserts the distal end 32 of the catheter 22 into the subject and then navigates the distal end 32 to the tissue to be ablated. For example, the physician can advance the distal end through the vasculature of the subject until the distal end contacts cardiac tissue belonging to the heart 24 of the subject. Next, when the distal end 32 contacts the tissue, the physician causes a radiofrequency (RF) current to be conducted between the distal end 32 and a neutral electrode patch 30 that is coupled to the exterior of the subject, such as to the back of the subject.

[0101] To facilitate navigation of the catheter, the catheter 22 can include one or more electromagnetic position sensors that generate signals that vary with the position of the sensors in the presence of an external magnetic field. Alternatively or additionally, any other suitable tracking system can be used, such as an impedance-based tracking system. For example, both electromagnetic tracking and impedance-based tracking can be used, as described, for example, in U.S. Patent 8,456,182, the disclosure of which is incorporated herein by reference.

[0102] The catheter 22 is connected proximally to a console 34 that includes, for example, a processor (PROC) 23, a pump 25, and a signal generator (GEN) 27. (Electrode patches 30 are typically also connected to the console 34 via wires 42). During an ablation procedure, the signal generator 27 generates the ablation current described above. These currents are delivered to the distal tip 32 through one or more wires passing through the catheter 22. Additionally, the pump 25 supplies a flushing fluid such as saline to the distal tip of the catheter, as further described below with reference to Figures 2A to 2B and Figure 3 further described.

[0103] The console 34 also includes a controller 35 that a physician can use to control the parameters of the ablation current. Specifically, in response to manipulation of the controller 35 by the physician 28, the processor 23 can adjust the parameters of the ablation current by outputting appropriate instructions to the signal generator 27 over any suitable wired or wireless communication interface. The processor 23 can similarly control the pump 25 over any suitable wired or wireless interface. Additionally, 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.

[0104] In some embodiments, the system also includes a display 38 that can display relevant outputs to the physician 28 during the procedure.

[0105] Although Figure 1 a particular type of procedure is depicted, 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 the transfer of heat through a flexible PCB. [[ID=?]]

[0106] [[ID=?]] Distal End of the Catheter [[ID=?]] [[ID=?]]

[0107] Now refer to Figure 2A , which is a schematic diagram of the distal tip 32 according to some embodiments of the present disclosure. Additionally refer to Figure 3 , which schematically shows a longitudinal cross-section of the distal tip 32 according to some embodiments of the present disclosure.

[0108] The distal tip 32 includes at least one ablation electrode 40, 30, such as Figure 2A and Figure 3 It should be noted that there are some tags with "?" in the original text which seem to be incorrect or incomplete. I have translated the text as accurately as possible based on the available information.The catheter tip electrode depicted therein. Electrode 40 includes a plated flexible thermal insulation substrate 41, which is adhesively bonded to a support structure 36 at the distal end of catheter 22. Substrate 41 can be made of any suitable flexible thermal insulation material (such as a flexible polymer (e.g., polyimide) or liquid crystal polymer (LCP)). Support structure 36 can be made of any sufficiently strong material (such as cobalt-chromium, stainless steel, magnesium, and / or an alloy of any of the above metals). For example, support structure 36 can include an L-605 cobalt-chromium-tungsten-nickel alloy.

[0109] Generally speaking, electrode 40 can have any suitable shape. In some embodiments, as Figure 2A and Figure 3 shown, electrode 40 is sleeve-shaped, which includes a cylindrical portion 40b capped by a dome-shaped portion 40a. Generally, the tab 47 located at the proximal end of the electrode includes a pad, on which a wire extending along the length of the catheter can be welded to establish an electrical connection between the electrode and the proximal end of the catheter. These pads are described in further detail below with reference to Figures 4 to 5

[0110] As Figure 2A shown in the "A-A" cross-section of, substrate 41 includes an inner surface 76 facing support structure 36 and an outer surface 45 facing away from support structure 36. Generally, the thickness T0 of the substrate (i.e., the distance between the inner surface and the outer surface of the substrate) is between 5 microns and 75 microns (e.g., between 12 microns and 50 microns). At least a portion of the inner surface is covered by an inner layer 70 of a thermally conductive metal (such as gold). Generally, inner layer 70 has a thickness T1 between 10 microns and 50 microns. Similarly, at least a portion of outer surface 45 is covered by a metal outer layer 50. Generally, outer layer 50 has a thickness T2 between 1 micron and 5 microns.

[0111] Generally, outer layer 50 is discontinuous because the outer layer includes a main portion 54 and one or more isolation portions, which are electrically isolated from main portion 54 by the exposed portions of the substrate. These isolation portions can include one or more "islands" serving as sensing microelectrodes 56. For example, outer layer 50 can include 3 to 7 microelectrodes 56 distributed circumferentially around the distal end. Alternatively or additionally, the isolation portion can include a sensing ring electrode 43, which can be disposed, for example, near the proximal end of distal end 32.

[0112] Corresponding conductive traces 78 electrically isolated from inner layer 70 by the exposed portions of inner surface 76 are disposed under each sensing electrode. As described below with reference to Figure 4 ​Further described, prior to forming the sensing electrodes, holes (e.g., drilled) are formed in the substrate above the traces 78, which are referred to herein as blind holes 80. Subsequently, when the sensing electrodes are deposited onto the outer surface of the substrate, the sensing electrodes at least partially fill the blind holes 80, thereby contacting the traces.

[0113] Thus, during the procedure, the electrogram signals from the subject's heart tissue sensed by the sensing electrodes can be transmitted through the traces 78 to the wires that pass through the catheter 22 to the proximal end of the catheter. The signals can thus be delivered to the processor 23 for analysis.

[0114] Now also referring to Figure 2B , which schematically shows a cross-section through a portion of the electrode 40 according to some embodiments of the present disclosure. Figure 2B Corresponding to the "B-B" cross-section indicated in Figure 2A .

[0115] The substrate 41 is shaped to define a plurality of channels including a plurality of narrower channels 46 and one or more wider channels 44 that pass between the inner and outer surfaces of the substrate. Generally, each channel tapers along the length of the channel, where 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 narrower channel 46 is less than the cross-sectional area (or average cross-sectional area) of each wider channel 44.

[0116] In some embodiments, the channels have a circular cross-section. In such embodiments, the average diameter d0 of each of the narrower channels in the narrower channels can be less than 50% (e.g., less than 25%) of the average diameter d1 of each of the wider channels in the wider channels. Alternatively or additionally, the diameter d0 can be between 5 microns and 50 microns (e.g., between 5 microns and 30 microns), and / or the diameter d1 can be between 50 microns and 300 microns. In other embodiments, at least some of the channels can have a square shape or any other suitable shape of cross-section. (In such embodiments, the average cross-sectional area of each of the channels can correspond to the cross-sectional area implied above by the ranges for d0 and d1.)

[0117] Generally, the electrode includes 30 to 100 wider channels. Each wider channel 44 is coated with a plating layer 52 of a conductive and thermally conductive metal, which connects the outer layer 50 to the inner layer 70. Thus, the coated wider channels provide electrical and thermal conductivity between the metal outer layer and the metal inner layer. In addition, the coated wider channels provide a fluid channel between the inside and outside of the distal end 32, such that by the pump 25 ( Figure 1)The supplied flushing fluid 39 can flow therethrough. Thus, the wider plated channels can be referred to as "flushing holes" 72. (The diameter of each flushing hole is smaller than the diameter d1 by approximately twice the thickness of the plating layer 52.) The support structure 36 is shaped to define an opening 62 aligned with the flushing holes 72 such that the support structure does not block the flushing holes.

[0118] Typically, the number of the narrower channels 46 is relatively large. For example, the substrate 41 can be shaped to define at least 1,000, 5,000, 10,000, or 20,000 narrower channels. Alternatively or additionally, the ratio of the narrower channels to the wider channels can be at least 300:1. Alternatively or additionally, the total area of the respective outer openings of the narrower channels (i.e., the openings of the narrower channels at 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 narrower channels) is 27 mm 2 , and each of the narrower channels in the narrower channels includes a circular outer opening with a diameter of 25 micrometers (and thus an area of 0.0005 mm 2 ), then the number of the narrower channels can be approximately 16,500 (with a total area of 8.1 mm 2 ), such that the outer openings of the narrower channels cover approximately 30% of the outer surface.

[0119] Contrary to the wider channels, the narrower channels 46 are not merely plated, but are filled with respective columns 48 of a thermally conductive metal, which connect the outer layer 50 to the inner layer 70. (Since, as described above, the narrower channels 46 do not necessarily have a circular cross-section, the columns 48 are not necessarily cylindrical. Additionally, as described above, the cross-sectional area of each column can vary along the length of the column.

[0120] Note that the outer layer 50, the inner layer 70, the plating layer 52, and the columns 48 can be collectively described as a single metal body covering the substrate.) Since the number of the channels 46 is large and since each of these channels is filled, a large amount of heat can be transferred via the channels 46. Thus, the filled narrower channels can be referred to as "heat dissipation holes" 74. (For ease of illustration, Figure 2A the heat dissipation holes are not shown in the "A-A" cross-section of.

[0121] Notwithstanding the above, note that in some embodiments, similar to the wider channels, the narrower channels are not filled but are merely plated. Even in such embodiments, a large amount of heat can be transferred into the electrode.

[0122] Typically, catheter 22 includes a fluid delivery tube (not shown) that extends along the entire length of the tubular body 22m of catheter 22. The fluid delivery tube is coupled distally to a flow diversion element 60 that is shaped to define one or more fluid flow openings 64. The flow diversion element 60 diverts fluid 39 received via the fluid delivery tube from the proximal end of the catheter through the fluid flow openings 64. In such embodiments, electrode 40 may be coupled to the base 58 of the flow diversion element 60 such that the flow diversion element is disposed inside the lumen of the electrode. For example, support structure 36 may be bonded to the base 58. Alternatively or additionally, the base 58 may be shaped to define a plurality of protrusions and the support structure 36 may be shaped to define a plurality of complementary holes such that the protrusions snap into the holes.

[0123] As described above with reference to Figure 1 During an ablation procedure, physician 28 contacts the tissue of subject 26 with the distal tip 32, and in particular with the outer layer 50. While contacting the tissue with the outer layer 50, the physician delivers an electric current through the outer layer into the tissue. The electric current causes heat to be generated in the tissue such that an ablation lesion is formed in the tissue. This heat is transferred to the inner layer 70 via the heat dissipation holes 74 (i.e., via the posts 48). At the same time, pump 25 ( Figure 1 ) pumps a flushing fluid 39 through the fluid delivery tube such that the fluid flows into the interior of the electrode through the fluid flow openings 64 of the flow diversion element 60. The fluid then exits the distal tip through the openings 62 and the flushing holes 72, thereby discharging the heat from the inner layer 70 into the subject's blood.

[0124] Manufacturing the Distal End

[0125] Now refer to Figure 4 , which is a flow chart of a method 400 for manufacturing an electrode 40 according to some embodiments of the present disclosure. Now also refer to Figure 5 , which is a schematic illustration of an electrode 40 prior to its deformation according to some embodiments of the present disclosure. ( Figure 5 The interior of the electrode 40 is shown, i.e., the various elements coupled to the inner surface of the substrate 41.)

[0126] Figure 4 It is assumed 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 other copper on the inner surface is etched away except for the copper traces 114 that will be connected to the sensing electrodes on the outside of the electrode. (Any copper on the outer surface 5 is also etched away.) For example, such etching may be performed by placing a mask over the copper portions designated for the traces 114 and then chemically removing the exposed copper. Alternatively, if the inner surface of the substrate is initially exposed, the copper traces 114 may be deposited on the inner surface.

[0127] Subsequently, at trace deposition step 86, a constantan trace 118 for the thermocouple is deposited onto the inner surface of the substrate. The trace deposition step 86 can be performed, for example, by physical vapor deposition (PVD) such as sputter deposition. For example, a mask can be placed over all inner surface portions other than those portions on the inner surface designated for the constantan traces 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.

[0128] Typically, to minimize the required wiring, the constantan traces terminate at a common constantan trace pad 120. In some embodiments, prior to depositing the constantan, holes (or “via studs”) are drilled through the substrate at the location of the pads 120. Subsequently, the deposited constantan fills the holes and then forms the pads 120 above the holes. Alternatively, a recess can be drilled into the substrate such that the deposited constantan fills the recess rather than drilling completely through the substrate. In either case, the pads 120 are “studded” to the substrate by the constantan beneath the pads. (To facilitate filling the holes or recesses, a draft angle can be used to taper the holes or recesses, as described immediately below for the narrower channels and wider channels.)

[0129] Next, at drilling step 88, multiple narrower channels as well as one or more wider channels 44 are drilled through the substrate, typically using laser drilling techniques. ( Figure 5 The wider channels can be seen in [FIGURE REFERENCE], but the narrower channels cannot be seen). Typically, the channels are drilled from the inner surface of the substrate, with a draft angle such that the channels taper as they approach the outer surface; this facilitates collecting metal onto the walls of the channels during subsequent sputtering processes. Additionally, blind holes 80 can be drilled (e.g., laser drilled) through the substrate from the outer surface at those portions of the outer surface designated for the sensing electrodes, where the copper trace 114 is used as a diaphragm. (In other words, the portions of the substrate disposed on the copper trace can be removed, thereby exposing the copper trace.) Typically, a draft angle is used for the blind holes such that the blind holes taper as they approach the inner surface of the substrate; this facilitates collecting metal onto the walls of the blind holes.

[0130] Next, at the first masking step 90, a mask is applied to the copper traces, the constantan traces, and the isolation regions 91 designated to isolate these traces (i.e., the exposed portions of the inner surface of the substrate). (The portions of the constantan traces designated for the thermocouple junctions are not masked.) A mask is also applied to additional isolation regions designated to isolate gold traces that will intersect the constantan traces (thereby forming constantan-gold thermocouples). Additionally, a mask is applied to the isolation regions on the outer surface designated to isolate the sensing electrodes.

[0131] Subsequently, at deposition step 92, a thin gold layer 30 is deposited on the inner and outer surfaces of the substrate and into the channels. The deposition step 92 can be performed, for example, by physical vapor deposition (PVD) such as sputter deposition. (Typically, a seed layer of a base metal such as titanium-tungsten is sputtered onto the substrate before sputtering gold.) By means of a mask, gold is not deposited onto the traces or isolation regions.

[0132] The deposited gold includes an initialization layer for the inner layer 70, the outer layer 50, the plating layer 52, and the pillars 48. The deposited gold also includes a gold trace 122 covering the constantan trace at the thermocouple junction 124. Each gold trace 122 terminates at a corresponding gold trace pad 126. The deposited gold also includes corresponding copper trace pads 116 for each copper trace. In some embodiments, the copper trace pads 116 and / or the gold trace pads 126 are staked to the substrate as described above for the constantan-trace pads. The deposited gold also includes at least one gold pad 128 that is connected to the inner layer 70. The gold pad 128 can also be staked to the substrate.

[0133] After deposition, at mask removal step 93, the mask (and any gold deposited on the mask) is removed. Subsequently, at a second masking step 94, a mask is applied to the traces, the inner surface isolation regions surrounding the traces, and the entire outer surface of the substrate.

[0134] After the second masking step 94, while keeping the traces and the outer surface masked, at a first plating step 98, the substrate is plated in a gold plating bath for a first time interval. The plating of the substrate fills any gaps in the gold and further increases the thickness of the gold such that, for example, the thickness of the inner layer 70 reaches between 5 microns and 40 microns, and the diameter of the wider channels is reduced to between 30 microns and 200 microns. Additionally, the narrower channels may be completely filled.

[0135] Typically, the plating of the substrate is electrochemical, whereby the flow of current through the gold that has already been coated on the substrate causes the gold to attract gold ions in the plating bath. The amplitude and duration of the current can be controlled such that the gold reaches the desired thickness.

[0136] After the first plating step 98, at a demasking step 100, the remaining inner and outer surface portions of the substrate except for the isolation regions designated above for isolating the sensing electrodes are demasked. Next, at an applied surface protection layer step 101, at least one surface protection layer 130 is applied over the traces and the inner surface isolation regions. (In some embodiments, as shown in the inserted portion of Figure 5 the surface protection layer 130 is transparent or nearly transparent.)

[0137] Typically, the proximal portion of the cover tab 47 of the sheet guard layer 130 is shaped to define a window 132 exposing the pad such that the pad can be thickened during a subsequent plating process. (An additional cover 142 having a window aligned with the window 132 may cover the proximal portion of the sheet guard layer.) Typically, the pad is not fully exposed but remains "tethered" by the sheet guard layer 130 as one or more edges of each pad are covered by the edges of the window 132. Thus, the sheet guard layer 130 helps to hold the pad on the substrate 41 during a subsequent soldering process.

[0138] Subsequently, at the second plating step 102, the substrate is plated in a plating bath for a second time interval such that any gaps in the outer layer 50 are filled while the inner layer, outer layer, and plating layer are all thickened. For example, the second plating may increase the thickness of the inner layer to be between 10 microns and 50 microns while reducing the diameter of the wider channels to be between 15 microns and 150 microns. Typically, the final thickness of the inner layer is the same as the thickness of the sheet guard layer in order 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 sheet guard layer and the inner gold layer, while the term "internal surface" is used to refer to the lower surface of the substrate.) Additionally, if the narrower channels were not fully filled during the first plating step 98, these channels are fully filled during the second plating step 102. As in the case of the first plating step 98, the amplitude and duration of the current in the plating bath can be controlled such that the desired thickness is obtained. (In some embodiments, a mask is applied to the outer surface prior to the deposition step 92 such that no gold is deposited on the outer surface during the deposition step 92. In such embodiments, a thin gold layer is deposited on the outer surface after the demasking step 100 and before the second plating step 102.)

[0139] After the second plating step 102, at the drilling step 104, an opening 62 is drilled through the support structure 36. (As an alternative to drilling, any other suitable technique (such as chemical etching) can be used to form the opening.) Next, at the bonding step 106, the support structure is bonded to the inner surface by applying a suitable adhesive between the support structure 36 and the smooth inner surface formed by the sheet guard layer 130 and the inner layer 70, wherein the opening 62 is aligned with the flushing hole 72. Typically, the area of the opening is larger than the area of the flushing hole in order to compensate for any minor misalignment when bonding the support structure.

[0140] Next, at the deformation step 108, the electrode 40 is deformed into a desired shape. For example, the electrode can be inserted into a forming fixture that shapes the electrode around a suitable mandrel. After the electrode is inserted into the fixture, the fixture is placed in an oven. Subsequently, the oven heats the electrode to a suitable temperature while applying pressure to the electrode. The combination of heat and pressure causes the electrode to bond itself into the desired shape.

[0141] Generally speaking, the base and the support structure can be deformed into any desired shape. However, typically during the deformation step 108, the base and the support structure are formed to define a lumen; for example, the base and the support structure can be formed to define a cannula containing the lumen, as described above with reference to Figure 2A and Figure 3 as described. Alternatively, for example, the base and the support structure can be formed to define a ring.

[0142] Typically, to facilitate the fabrication of the cannula-shaped electrode, the base 41 includes two portions that are continuous with each other: a distal circular portion 41a and a proximal rectangular portion 41b. Similarly, the support structure 36 includes two portions that are continuous with each other: a distal support portion 36a, which typically includes a plurality of spokes 134 radiating 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 Figure 5 ). Additionally, the proximal support portion 36b is bonded to the inner surface of the rectangular portion 41b, leaving some distal portions of this inner surface exposed. An adhesive is applied to the outer surface of the overhanging tab 138 of the proximal support portion 36b, which overhangs the side of the rectangular portion 41b. (The proximal support portion 36b can also overhang the proximal end of the rectangular portion 41).

[0143] Subsequently, during the deformation step 108, the distal support portion 36a and the circular portion 41a are folded over the top of the mandrel, while the proximal support portion 36b and the rectangular portion 41b are rolled around the mandrel. To maintain this configuration, the outer surface of the spokes 134 is bonded to the exposed distal portion of the inner surface of the rectangular portion 41b, and the outer surface of the tab 138 is bonded to the opposite end of the proximal support portion 36b. (Additionally, the inner surface of at least one spoke can be bonded to the tab 138). Thus, the distal support portion 36a and the circular portion 41a are formed into a dome-shaped portion 40a ( Figure 2A ), while the proximal support portion 36b and the rectangular portion 41b are formed into a cylindrical portion 40b.

[0144] Subsequently, at the welding step 110, the wires are welded to the pads. Specifically, the wire that delivers the RF current from the generator 27 ( Figure 1 ) is welded to the gold pad 128, while the other wires that deliver signals to the processor 23 are welded to the other pads.

[0145] Finally, at the coupling step 112, the electrode is coupled to the catheter. For example, the proximal support portion 36b can be bonded to the base 58 of the current shunt elementFigure 3 )。Alternatively or additionally, as described above with reference to Figure 3 Figure 3 , the protrusion belonging to the base 58 can be snapped into the complementary hole 140 in the proximal support part 36b. Subsequently, the flow diversion element can be coupled to the fluid delivery tube belonging to the catheter. (Alternatively, the flow diversion element can be coupled to the fluid delivery tube before coupling the electrode to the flow diversion element).

[0146] Some known ablation catheters are constructed of a double-sided flexible circuit, and the external metal of the circuit is used to form the catheter tip electrode for ablation. However, in these known methods, the polymer layer between the external metal and the internal metal can produce significant heat resistance and is used to maintain the elevation of the outer surface temperature. A solution to these and other problems is shown in Figures 6 to 8 Figures 6 to 8 , whereby, by means of a plurality of heat dissipation holes 80 (e.g., thousands of through-holes 80) formed in the polymer layer, the solution depicted significantly increases the heat transfer through the polymer layer (e.g., PCB). The through-holes 80 electrothermally bond the outer metal layer 70 to Figures 6 to 8 the inner metal layer 50 of the example described, thereby allowing heat transfer from the outside to the inside, where the temperature of the tip 32 can be cooled by the saline solution used for flushing. Figures 6 to 8 The through-holes 80 shown can be solid cylinders, typically gold, or at least some can be plated through the through-holes, thereby allowing the flushing liquid to be transferred to the outside.

[0147] At least because the heat flow from the central (and hottest) region of the ablation zone is very dependent on the thermal conductivity of the tip 32 when the tip 32 is positioned above the hottest part of the tissue, the layers 50, 70 are thermally conductive and are particularly effective in transferring heat away from the tissue. Subsequently, the heat flow through the catheter tip 32 is increased by providing a heat path from the tissue, including the heat flow into the fluid (e.g., flushing fluid and / or blood). The heat comes from the outside, and the outer thermally conductive layer 70 transfers some of it directly to the blood. Part of the heat flow passes through the heat bridge, which is described more specifically below. In this regard, the plated flushing holes described herein transfer some of the heat in the heat to the flushing fluid, reach the inner layer 50, and the inner layer 50 can transfer the remaining heat to the flushing fluid through its surface. The flushing fluid flowing through the plated holes loses some heat to the walls of the flushing holes after leaving the catheter tip 32 and mostly loses it to the blood.

[0148] The purpose of the thermally conductive layers 50, 70 is to increase the heat flow inside, thereby providing the maximum contact area with the cooling fluid flow (e.g., blood, flushing fluid, etc.). The layers 50, 70 are also effective in terms of effective heat transfer between the layers to increase the contact area. The layers 50, 70 are also effective in simulating the structure of a fully metal tip, where cooling occurs from all surfaces exposed to the liquid.

[0149] Specifically, Figure 6A perspective view of the distal end 32 of an exemplary configuration of the ablation catheter 22 of the present disclosure is shown. As discussed more specifically below, the end 32 may include a PCB 160 (shown more specifically in Figures 7A to 7B ), to which a domed portion 40a and a cylindrical portion 40b are attached or otherwise formed. For example, the PCB 160 may be wrapped with an inner layer 70 and an outer layer 50, where the flushing holes 72 and the corresponding electrodes of the end 32 face the internal tissue of the heart 24. Figure 6 The configuration of the distal end 32 shown is an example configuration chosen solely for the sake of conceptual clarity. In alternative embodiments, any other suitable configuration may be used.

[0150] Figures 7A to 8 An exemplary distal end 32 configuration of the ablation catheter 22 of the present disclosure is shown. Specifically, Figure 7A An internal perspective view of the distal end 32 at a cross-section along the centerline of the distal end 32 is shown to illustrate the inner surface of the catheter end 32, while Figure 8 An external perspective view of the same exemplary end 32 is shown. It can be seen that the end 32 in the example shown includes a cylindrical portion 40b and a domed portion 40a, each of which includes selectively positioned flushing holes 72 and blind holes 80. The blind holes 80 may be provided to obtain electrical conductivity such that the inner layer 70 is in direct contact with the outer layer 50, and an exemplary distance between each blind hole 80 may be from about 0.2 mm to 0.3 mm. The flushing holes 72 of the depicted example may themselves be heat transfer through-holes (e.g., are gold-plated walls).

[0151] Now referring to Figure 7B , which schematically shows a close-up longitudinal section through C-C of the distal end 32. It can be seen that the depicted example is a bi-metal layer, whereby the inner layer 70 and the outer layer 50 are shown and are constructed of metal. The PCB 160 may be sandwiched therebetween and has a plurality of selectively positioned through-holes 80 (e.g., heat bridges). The inner layer 70 and the outer layer 50 may be constructed of gold, and their typical thicknesses may each be about 40 microns. In this example, the typical diameter of the through-holes 80 may be about 60 microns. The typical thickness of the wall plating in the flushing holes 72 of this example may be about 25 microns. The typical thickness of the PCB layer 160 of this example may be about 50 microns. Thus, Figure 7A The total outer shell thickness of the catheter end 32 shown may be about 130 microns (i.e., 0.13 mm).

[0152] Various aspects of the solution disclosed by the present invention can be more fully understood from the following description of some exemplary embodiments and the corresponding results. Some of the experimental data presented herein are for illustrative purposes and should not be construed as limiting the scope of the disclosed technology in any way or excluding any alternative or additional embodiments.

[0153] Reference will now be made Figure 9 to a first example of certain specific implementations of the technology disclosed by the present invention and corresponding results, where graphical descriptions showing the results from a finite element simulation (COMSOL) are provided, the finite element simulation being performed to compare the performance of a PCB-based catheter tip utilizing an interconnecting metal layer with the performance of a catheter tip without such components of the present invention (hereinafter referred to as a "standard flexible circuit"). The simulation parameters for both the standard flexible circuit and the bimetallic layer example are substantially the same with respect to both ablation conditions (e.g., time, ablation current, flushing, position of the ablation catheter, etc.) and the environment including blood and tissue having associated thermoelectric properties and geometries. The ablation catheter 22 for the exemplary analysis is set at a 45° angle to the tissue, with a penetration depth of 0.8 mm, which is considered typical and normal operating conditions. Two scenarios are analyzed, including a first scenario where the ablation current is set to approximately 0.63 amperes and maintained for up to 30 seconds, equivalent to 30W - 40W, depending on the measured impedance. The results of this first scenario are shown in Figure 9 and Figure 10 . The second scenario includes setting the ablation current to 0.9 A and maintaining it for up to 5 s, equivalent to 80W - 100W, depending on the measured impedance. The safety of both scenarios is evaluated at temperatures above 130 °C, as such temperatures are considered dangerous and highly likely to cause tissue rupture due to steam accumulation (e.g., steam burst).

[0154] Turning to Figure 9 , which shows the results of the first scenario, in the case of the distal tip of the standard flexible circuit, the temperature field is depicted as being up to approximately 130 °C. Specifically, it can be seen that the distal tip 32 has been positioned on the ablation surface and held with an ablation current of approximately 0.63 amperes for approximately 4.7 seconds, resulting in an ablation lesion width of approximately 4.6 mm and an ablation lesion depth of approximately 3.0 mm. Figure 10 Depicts the temperature field of up to approximately 130 °C for the distal tip of the exemplary bimetallic layer ablation catheter. Specifically, it can be seen that the distal tip 32 has been positioned on the ablation surface and held with an ablation current of approximately 0.63 amperes for 30 seconds, resulting in an ablation lesion width of approximately 8.9 mm and an ablation lesion depth of approximately 5.6 mm. In other words, when compared with the depicted results of the distal tip of the standard flexible circuit, the bimetallic layer distal tip (e.g., Figures 7A to 8 a similar implementation of the tip 32 shown) exhibits an increase in ablation lesion width of approximately 93.5% (i.e., from approximately 4.6 mm to approximately 9.6 mm), an increase in ablation lesion depth of approximately 86.7% (i.e., from approximately 3 mm to approximately 5.6 mm), and an increase in ablation time believed to be clinically safe of approximately 538.3% (i.e., the ablation time between observed unsafe temperatures, from approximately 4.7 seconds to approximately 30 seconds). In other words, Figures 7A to 8The configuration of the catheter tip 32 is significantly safer, more effective, more durable, and provides a larger ablation zone compared to a standard flexible circuit tip at an ablation current of approximately 0.63 amperes.

[0155] Go to Figure 11 , which shows the results of the second scenario. In the case of the distal tip of the standard flexible circuit, the temperature field is depicted as being up to approximately 130°C. Specifically, it can be seen that the distal tip 32 of the catheter 22 has been positioned on the ablation surface and held for 1.7 seconds with an ablation current of approximately 0.90 amperes, resulting in an ablation lesion width of 4.3 mm and an ablation lesion depth of 2.6 mm. Figure 12 Depicts the temperature field of up to approximately 130°C for an exemplary bimetallic layer distal tip ablation catheter. Specifically, it can be seen that the distal tip 32 has been positioned on the ablation surface and held for 4.5 seconds with an ablation current of approximately 0.90 amperes, resulting in an ablation lesion width of approximately 6.9 mm and an ablation lesion depth of approximately 3.6 mm. In other words, when compared to Figure 11 the depicted results of Figures 7A to 8 the bimetallic layer distal tip (e.g., a similar embodiment of the tip 32 shown in [[ID=E1]]), shows an increase in ablation lesion width of approximately 60.5% (i.e., from 4.3 mm to 6.9 mm), an increase in ablation lesion depth of approximately 38.5% (i.e., from 2.6 mm to 3.6 mm), and an increase in ablation time believed to be clinically safe of approximately 164.7% (i.e., the ablation time between observed unsafe temperatures, from approximately 1.7 seconds to approximately 4.5 seconds) at an ablation current of approximately 0.90 amperes. In other words, Figures 7A to 8 the configuration of the catheter tip 32 shows to be believed safer, more effective, more durable, and provides a larger ablation zone compared to a standard flexible circuit tip at an ablation current of approximately 0.90 amperes.

[0156] Figure 13 Shows a heat flux diagram in the case of a bimetallic layer constructed of platinum and connected through the heat dissipation holes 80 of the exemplary PCB 160. Thus, the catheter 22 is positioned at an angle of approximately 45° to the tissue during the simulation and held for 30 seconds with an insertion of 1 mm.

[0157] Figure 14 Shows a temperature diagram in the case of a bimetallic layer constructed of platinum and connected through the heat dissipation holes 80 of the exemplary PCB 160. Thus, the catheter 22 is positioned in a vertically inserted manner (e.g., at an angle of approximately 90° to the tissue) and held for 2.5 seconds.

[0158] Figure 15 Note: There seems to be a missing reference in the text where "e.g., [[ID=E1]]" is mentioned, but the content within the brackets is not provided. This might cause some confusion in the overall understanding of the text, but the translation is done based on the available information.A graph showing the maximum temperature in tissue during ablation between a standard flexible circuit and the distal end 32 of a bimetallic layer catheter. During ablation, an ablation current of approximately 0.63 amperes (~35 W) was shown for an ablation duration of 0 s - 30 s, with a temperature range of approximately 40°C - 220°C. It can be seen that the temperature curve of the distal end of the standard flexible circuit reaches the temperature safety limit of 130°C after an ablation time of approximately 5 seconds. In contrast, even after an ablation time of 30 seconds, the distal end of the bimetallic layer catheter of the present disclosure never fully reaches the temperature safety limit of 130°C.

[0159] Figure 16 A graph showing the maximum temperature in tissue during ablation between a flexible distal catheter end and the distal end 32 of a bimetallic layer catheter. During ablation, an ablation current of 0.9 A (equivalent to ~90 W) was shown for an ablation time of 0 s - 5 s, with a temperature range of approximately 40°C - 245°C. It can be seen that the temperature curve of the distal end of the standard flexible circuit reaches the temperature safety limit of 130°C after an ablation time of approximately 4.5 seconds. In contrast, the distal end of the bimetallic layer catheter of the present disclosure reaches the temperature safety limit of 130°C after an ablation time of approximately 1.7 seconds.

[0160] Figure 17 A perspective view showing the heat generated at approximately 1.5 W in a hemisphere with a radius of approximately 2 mm under an exemplary illustration of the distal end 32 of the bimetallic layer of the catheter 22 of the present disclosure. The depicted hemisphere is generally located at the position where the ablation center of the distal end 32 is approximately located. Of course, the depicted hemisphere only represents one embodiment, and other shapes of ablation regions and ablation radii can be envisioned according to the solutions of the present disclosure.

[0161] Figure 18 A perspective view showing an exemplary embodiment of the distal end of the bimetallic layer of a catheter in contact with tissue. Through Figure 18 The total heat flux through the surface of the distal end 32 is approximately -0.82 W, while for the distal end of the standard flexible circuit of the present disclosure, this total heat flux is approximately -0.3 W. Thus, out of the initial 1.5 W, 0.7 W is retained in the distal end of the bimetallic layer, while 1.2 W is retained in the standard flexible circuit, an increase of approximately 71.5%. Other cases (e.g., a single metal layer) are shown as falling between the extreme cases. Although the foregoing oversimplifies the various features and systems, it is relatively clear that in the absence of an effective cooling method in the hotter regions of the distal end 32, the ablation zone will form a high enough temperature to prevent the formation of an ablation lesion exceeding a specific size within the safety limit.

[0162] Figure 19A flowchart of a method according to some embodiments of the present disclosure. Step 1910 includes inserting a distal end of a catheter into 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 thermal bridges selectively positioned between the inner and outer layers and passing through the polymer layer, thereby significantly increasing heat transfer through the polymer layer at the catheter tip. Step 1920 includes delivering an ablation current through the outer layer into the tissue while in contact with the tissue, such that heat is generated in the tissue and the heat is transferred through the thermal bridges to the inner thermally conductive layer. Step 1930 includes contacting the subject's tissue with the outer layer after inserting the distal end of the catheter into the subject's body. Step 1940 includes discharging heat from the inner thermally conductive layer into the subject's blood by passing a flushing fluid through a plurality of flushing channels through the inner layer, the outer layer, and the polymer layer.

[0163] Figure 20 A flowchart of a method 2000 for manufacturing a catheter tip electrode according to some embodiments of the present disclosure. Step 2010 includes drilling a plurality of thermal bridges through a flexible thermally insulating polymer substrate. Step 2020 includes sandwiching the flexible thermally insulating polymer substrate between an inner surface and an outer surface using a thermally conductive metal. It should be understood that any thermally conductive material can be used in the examples disclosed herein, including diamond. The catheter tip electrode can also be a separate thin (e.g., about 1 micron) metal layer deposited on a thermally conductive layer.

[0164] As an alternative or addition to the traces described above, any other suitable electrical or electronic components can be deposited on the inner surface of the substrate. Such components can include a thermistor for measuring tissue temperature, a pressure sensor for measuring the pressure applied to the distal end of the catheter, and / or an electromagnetic sensor for navigating the catheter. Whenever such a masking or covering operation is required, these components (and suitable surrounding isolation areas) can be masked or covered as described above for the traces.

[0165] Note that the scope of the present disclosure includes any suitable modifications to method 82 with respect to the order of performing steps and / or with respect to the various materials used, which 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.

[0166] Generally speaking, the embodiments described herein can be combined with any of the embodiments described in U.S. Patent Application Publication 2018 / 0110562 or U.S. Patent Application No. 15 / 793126, the disclosures of each of which are incorporated herein by reference.

[0167] Those skilled in the art should understand that the present disclosure is not limited to what is specifically shown and described above. Instead, the scope of the embodiments of the present disclosure includes both combinations and sub - combinations of the various features described above, as well as variations and modifications that may occur to those skilled in the art upon reading the above - mentioned specification and that are not within the scope of the prior art. Documents incorporated by reference into this patent application are considered an integral part of this application, except that if any terms defined in these incorporated documents conflict with the definitions expressly or implicitly given in this specification, only the definitions in this specification shall be considered.

Claims

1. An end of an electrophysiological catheter for ablation, the catheter end comprising: An outer layer of electrically and thermally conductive metal, the outer layer having a thickness of about 40 microns; An inner layer of electrically and thermally conductive metal, the inner layer having a thickness of about 40 microns; A polymer layer between the inner layer and the outer layer, wherein the polymer layer is a printed circuit board (PCB) having a thickness of about 50 microns; And A plurality of thermal bridges positioned between the inner layer and the outer layer and passing through the polymer layer, the plurality of thermal bridges increasing heat transfer through the polymer layer of the catheter end such that when the catheter end is set at an angle of 45° to tissue, with a penetration depth of 0.8 mm and delivering about 0.63 amperes to the outer layer of the end, ablation can be performed for 30 seconds and the temperature of the catheter end does not exceed 130°C; and when delivering about 0.90 amperes to the outer layer of the end, ablation can be performed for 4.5 seconds and the temperature of the catheter end does not exceed 130°C, Wherein the diameter of each of the plurality of thermal bridges is about 60 microns.

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

3. The catheter tip according to claim 1, wherein, The thermal bridges are thermally and electrically joined to the inner layer and the outer layer, thereby allowing heat transfer from the outside to the inside of the catheter end, and the temperature can be cooled by the saline used during flushing.

4. The catheter tip according to claim 1, wherein, The thermal bridges include solid cylinders, thereby allowing the flushing liquid to transfer heat to the outside.

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

6. The catheter end according to claim 1, further comprising: A plurality of electrodes oriented to contact cardiac tissue; And A plurality of metal flushing holes provided between the inner layer and the outer layer.

7. The catheter tip according to claim 6, wherein, The thickness of the wall plating in the flushing holes is about 25 microns.

8. The catheter tip according to claim 6, wherein, The catheter end includes a total outer shell thickness of about 130 microns.

9. The catheter tip according to claim 6, wherein, The catheter end is configured to generate a heat-generating hemispherical ablation zone with a radius of at least about 2 mm.

10. The catheter end according to claim 6, further comprising: A cylindrical segment; And A dome segment distal to the cylindrical segment, wherein the thermal bridges are positioned in the cylindrical segment and the dome segment.

11. A method for manufacturing an end of an electrophysiological catheter for ablation, comprising: Manufacturing an end of an electrophysiological catheter for ablation by: Drilling a plurality of thermal bridges through a flexible adiabatic polymer substrate having a thickness of about 50 microns, wherein the diameter of each of the plurality of thermal bridges is about 60 microns, wherein the flexible adiabatic polymer substrate is a printed circuit board (PCB); Clamping the flexible adiabatic polymer substrate between an inner layer and an outer layer of a thermally conductive bimetallic layer, the inner layer and the outer layer each having a thickness of about 40 microns; Wherein, the heat bridge increases the heat transfer of the catheter tip through the flexible adiabatic polymer substrate, such that when the catheter tip is set at an angle of 45° with respect to the tissue, with a penetration depth of 0.8 mm and delivering approximately 0.63 amperes to the outer layer of the thermally conductive bimetallic layer, ablation can be performed for 30 seconds with the temperature of the catheter tip not exceeding 130°C; and when delivering approximately 0.90 amperes to the outer layer of the thermally conductive bimetallic layer, ablation can be performed for 4.5 seconds, wherein the ablation current is 0.90 amperes and the temperature of the catheter tip does not exceed 130°C.

12. The method according to claim 11 further comprises: A plurality of flushing holes are drilled through the inner layer, the outer layer, and the adiabatic polymer substrate, the flushing holes having a diameter greater than that of the heat bridge.

13. The method according to claim 11, further comprising: Bonding the inner layer of the thermally conductive bimetallic layer to a support structure of the catheter tip; And Shaping the substrate and the support structure to define a lumen.

14. The method according to claim 13, wherein, Shaping the substrate and the support structure includes shaping the substrate and the support structure to define a cannula containing the lumen; And Connecting the support structure to the distal end of a catheter configured for insertion into a subject's body.

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