Patent Publication Number: US-2019175262-A1

Title: Balloon catheter distal end comprising electrodes and thermocouples

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to catheters, and particularly to balloon catheters and methods and systems for producing balloon catheters. 
     BACKGROUND OF THE INVENTION 
     Balloon catheters may be used in various medical procedures, such as in cardiac ablation. Several techniques for producing balloon catheters are known in the art. 
     For example, U.S. Pat. No. 6,500,174 describes a medical balloon catheter assembly that includes a balloon having a permeable region and a non-permeable region. The balloon is constructed at least in part from a fluid permeable tube such that the permeable region is formed from a porous material, which allows a volume of pressurized fluid to pass from within a chamber formed by the balloon and into the permeable region sufficiently such that the fluid may be ablatively coupled to tissue engaged by the permeable region. 
     U.S. Pat. No. 5,865,801 describes a balloon catheter that includes an elongate pliable catheter tubing with a dilatation balloon fixed to the catheter tubing near its distal end. The dilatation balloon includes a first wall for dividing the balloon into a plurality of dilatation compartments adjacent one another and arranged angularly about the catheter tubing. 
     U.S. Pat. No. 5,275,597 describes a catheter combination using a percutaneous transluminal transmitter for transmitting energy to a localized area. The combination includes a catheter having a hollow tubular member. A transmitter combination for partial insertion into the catheter includes a continuous central conductor terminating in a tip for receiving and transmitting a signal to the tip. 
     SUMMARY OF THE INVENTION 
     An embodiment of the present invention that is described herein provides a method for producing a medical instrument, the method includes coupling a balloon-based distal end of the medical instrument to a jig that sets the distal end to an expanded position. While the distal end is coupled to the jig, one or more electrodes are disposed on an outer surface of the distal end, one or more openings are formed in a wall of the distal end, and are threaded through the openings respective leads coupled to at least one of respective sensors and electrodes that are mounted on the outer surface of the distal end. One or more patches that cover the openings and couple the at least one of respective sensors and electrodes to the outer surface of the distal end, are coupled on the outer surface of the distal end. 
     In some embodiments, forming the openings includes cutting a latitudinal opening in the wall of the balloon-based distal end. In other embodiments, the sensors include one or more thermocouples (TCs). In yet other embodiments, coupling the balloon-based distal end to the jig includes inserting the balloon-based distal end into a hollow templates having one or more patterned openings. 
     In an embodiment, depositing the electrodes includes sputtering atoms or ions through the patterned openings. In another embodiment, sputtering the atoms or ions includes impinging electrons or ions on a sputtering target. In yet another embodiment, the method includes, before depositing the electrodes through the patterned openings, attaching the outer surface of the balloon-based distal ends to an inner surface of the hollow template, by creating vacuum around the balloon-based distal ends. 
     In some embodiments, the balloon-based distal end includes an inflatable balloon made from polyethylene terephthalate (PET). In other embodiments, the balloon-based distal end includes an inflatable balloon made from polyurethane. In yet other embodiments, the balloon-based distal end includes an inflatable balloon made from polyether block amide. 
     In an embodiment, coupling the one or more patches that cover the openings includes sealing the openings. In another embodiment, coupling the one or more patches includes cementing the at least one of respective sensors and electrodes to the outer surface of the distal end. 
     In some embodiments, the electrodes include one or more ablation electrodes. In other embodiments, the sensors include one or more electrophysiology (EP) sensing electrodes. 
     The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic, pictorial illustration of a catheter-based tracking and ablation system, in accordance with an embodiment of the present invention; 
         FIG. 2  is a schematic, pictorial illustration of a balloon assembly, in accordance with an embodiment of the present invention; 
         FIG. 3  is a flow chart that schematically illustrates a method for producing a balloon assembly of a catheter distal end, in accordance with an embodiment of the present invention; and 
         FIG. 4  is a schematic, sectional view of a balloon assembly contained within a production jig, in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Overview 
     Balloon catheters are used, for example, in various interventional cardiology procedures, such as in treating arrhythmia, by ablating tissue so as to form a lesion that blocks electrical conduction along a path of the tissue in a patient heart. A lesion that blocks undesired intra-heart electrical signals may be formed using various techniques, such as by electrophysiology (EP) mapping of the tissue, followed by applying a radio-frequency (RF) ablation to the tissue at one or more selected locations. In principle, monitoring the ablation process can be carried out using sensors mounted on the balloon catheter. 
     A catheter used for ablation may comprise an inflatable balloon assembly having an array of devices, such as ablation electrodes and sensors, mounted on an outer surface of the balloon assembly. The electrodes and sensors typically exchange electrical signals with a proximal end of the balloon catheter, via electrical leads. In some cases, such balloon assemblies have no openings via which the electrical leads can be connected to the devices mounted on the outer surface of the balloon assembly. 
     Embodiments of the present invention that are described hereinbelow provide improved techniques for depositing electrodes and/or mounting sensors of various types, such as thermocouples (TCs), on an outer surface of a balloon-based distal end of a catheter. These techniques are further used for electrically connecting the electrodes and/or sensors to the proximal end of the catheter using a single production setup. 
     In some embodiments, during production, the balloon-based distal end is coupled to a jig, which is configured to set the distal end to an expanded position. The following process steps are carried out while the distal end is coupled to the jig:
         Electrodes are deposited on using sputtering process, and one or more TCs are mounted on the outer surface of a wall of the distal end.   One or more openings are formed at given locations of the wall of the distal end, and electrical leads that typically extend from the catheter proximal end, are threaded through the openings and electrically coupled to the electrodes and/or TCs.   One or more patches are coupled to the given locations on the outer surface of the distal end so as to cover the respective openings and to couple the respective TCs to the outer surface of the balloon-based distal end.       

     In the context of the present disclosure and in the claims, the terms “balloon,” “balloon-based distal end” and “balloon assembly” are used interchangeably and refer to any suitable medical balloon catheter. 
     Medial catheters produced using the disclosed techniques are highly functional, due to the sputtering of high quality electrodes on the balloon catheter. The disclosed techniques enable seamless integration of various sensors and respective leads into the catheters. 
     Furthermore, the disclosed techniques reduce the production cost of the balloon catheter because multiple process steps are applied with the distal end coupled to a jig. 
     System Description 
       FIG. 1  is a schematic, pictorial illustration of a catheter-based tracking and ablation system  20 , in accordance with an embodiment of the present invention. System  20  comprises a catheter  22 , in the present example a cardiac catheter, and a control console  24 . In the embodiment described herein, catheter  22  may be used for any suitable therapeutic and/or diagnostic purposes, such as ablation of tissue in a heart (not shown). 
     Console  24  comprises a processor  34 , typically a general-purpose computer, with suitable front end and interface circuits  38  for receiving signals via catheter  22  and for controlling the other components of system  20  described herein. 
     Reference is now made to an inset  23 . A physician  30  inserts a medical instrument, such as catheter  22 , through a blood vessel  26  of the vascular system of a patient  28  lying on a table  29 . Catheter  22  comprises a balloon-based distal end assembly, such as a balloon assembly  40  fitted at its distal end. In some embodiments, assembly  40  comprises an inflatable balloon having a wall (shown in  FIG. 2  below) made from polyethylene terephthalate (PET), or from polyurethane, or from a thermoplastic elastomer, such as polyether block amide, or from any other suitable flexible material. In some embodiments, balloon assembly  40  comprise electrodes  42  that may be used for multiple purposes, such as electrophysiology (EP) mapping of tissue, or for ablating tissue at a target location of the heart. 
     In some embodiments, ablation electrodes  42  are deposited on the outer surface of balloon assembly  40  using a suitable geometrical pattern that fits the shape of the organ in question and the corresponding medical procedure (e.g., EP mapping, tissue ablation). 
     Several techniques may be used for applying the deposition, such as sputtering techniques, as will be described in detail in relation to  FIG. 2   3  below. 
     In some embodiments, balloon assembly  40  may comprise one or more sensors, such as thermocouples (TCs) (shown in  FIG. 2  below) configured to measure tissue temperature, so as to monitor the ablation procedure. 
     In other embodiments, balloon assembly  40  may comprise any additional or alternative suitable kinds of sensors, such as electrodes used for EP mapping tissue in the heart of patient  28 . 
     During the insertion of catheter  22 , balloon assembly  40  is contained in a sheath (not shown) in a collapsed position. In an embodiment, physician  30  navigates balloon assembly  40  in the vicinity of the target location in the heart by manipulating catheter  22  with a manipulator  32  near the proximal end of the catheter. The proximal end of catheter  22  is connected to interface circuitry in processor  34 . 
     In an embodiment, after navigating assembly  40  to the target location, physician  30  may inflate balloon assembly  40  so as to make physical contact between electrodes  42  and tissue at the target location. In an embodiment, electrodes  42  are configured to receive electrical ablation signals, such as radio-frequency (RF), via suitable wires that run through catheter  22 , and to ablate tissue at the target location in the patient heart. 
     As noted above, the temperature of the ablation procedure may be monitored using the TCs of assembly  40 . The ablation procedure is typically carried out at a predefined temperature range so as to enable the formation of a desired lesion without causing heart damage that may risk the safety of patient  28 . 
     In some embodiments, the position of balloon assembly  40  in the heart cavity is measured by a position sensor (not shown) of a magnetic position tracking system. In this case, console  24  comprises a driver circuit  41 , which drives magnetic field generators  36  placed at known positions external to patient  28  lying on table  29 , e.g., below the patient&#39;s torso. The position sensor is configured to generate position signals in response to sensed external magnetic fields from field generators  36 . The position signals are indicative of the position of balloon assembly  40  in the coordinate system of the position tracking system. 
     This method of position sensing is implemented in various medical applications, for example, in the CARTO™ system, produced by Biosense Webster Inc. (Irvine, Calif.) and is described in detail in U.S. Pat. Nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612 and 6,332,089, in PCT Patent Publication WO 96/05768, and in U.S. Patent Application Publications 2002/0065455 A1, 2003/0120150 A1 and 2004/0068178 A1, whose disclosures are all incorporated herein by reference. 
     Processor  34  typically comprises a general-purpose computer, which is programmed in software to carry out the functions described herein. The software may be downloaded to the computer in electronic form, over a network, for example, or it may, alternatively or additionally, be provided and/or stored on non-transitory tangible media, such as magnetic, optical, or electronic memory. 
     Integrating Thrmocouples in a Balloon Catheter 
       FIG. 2  is a schematic, pictorial illustration of balloon assembly  40 , in accordance with an embodiment of the present invention. In some embodiments, balloon assembly  40  comprises a wall  54  having an inner surface  52  and an outer surface  55 , which are coupled to the distal end of catheter  22 . 
     In some embodiments, balloon assembly  40  comprises electrodes  42  deposited on outer surface  55  using, for example, a sputtering process. In some embodiments, during production, balloon assembly  40  may be coupled to a jig (shown in  FIG. 4  below), which is configured to set balloon assembly  40  to an expanded position during the sputtering process. The production process of balloon assembly  40  is described in detail in  FIG. 3  below. 
     In some embodiments, balloon assembly  40  further comprises one or more TCs  44  mounted on outer surface  55  of assembly  40 . In some embodiments, each TC  44  is configured to sense the temperature of tissue in contact with outer surface  55 , and to produce electrical signals indicative of the sensed temperature. 
     In some embodiments, each TC  44  is coupled to a respective electrical lead  46  comprising two electrically isolated wires, which extends through the internal volume of balloon assembly  40 , via catheter  22 , to processor  34  or to any suitable interface of console  24 . In some embodiments, leads  46  are configured to conduct the electrical signals between TC  44  and processor  34 . 
     In some embodiments, leads  46  may be arranged in any suitable configuration. In an embodiment, each lead  46  may extend directly between TC  44  and processor  34 , such that multiple leads  46  may be arranged, for example, in a braid within catheter  22 . 
     In an alternative embodiment, lead  46  may be electrically connected, e.g., via a connector located at the distal end of catheter  22 , to a common electrical wire that extends between the connector and processor  34 . 
     In some embodiments, balloon assembly  40  comprises one or more openings  48 . In some embodiments, in producing the balloon, opening  48  may be formed by one or more horizontal cuts on respective latitudes along the circumference of wall  54  of balloon assembly  40 , as shown in  FIG. 2 . In this configuration, some or all of TCs  44  are threaded at the same latitudinal of balloon assembly  40 . 
     In other embodiments, any other suitable configuration of the openings may be applied. For example, the openings may comprise roundly-shaped holes at specific locations of wall  54 . Alternatively or additionally, vertical cuts along one or more longitudes of wall  54  may be used to form the openings in balloon assembly  40 . 
     In some embodiments, openings  48  are formed and leads  46  are threaded through openings  48 , while balloon assembly  40  is still coupled to the jig (e.g., before or after depositing electrodes  42 ). 
     In some embodiments, leads  46  are threaded through openings  48  such that each TC  44  is mounted on outer surface in close proximity to opening  48 . In alternative embodiments, TC  44  are mounted not necessarily with close proximity to openings  48 . 
     In some embodiments, balloon assembly  40  further comprises one or more patches  50 , which are configured to adhere to outer surface  55 , using glue material or using any other suitable technique. 
     In some embodiments, each patch  50  is adapted to cover a respective opening  48  so as to prevent unintended flow of fluids (e.g., blood and/or irrigation fluid) through openings  48 , between the internal volume of assembly  40  and the body of patient  28 . This configuration enables inflation (e.g., using a saline solution) and deflation of balloon assembly  40  in a controlled manner, typically through proximal end  32 . 
     In some embodiments, after creating patches  50 , and electrodes  42 , irrigation holes (not shown) can be made in the balloon allowing for an irrigation path into the patient. 
     In some embodiments, each patch  50  is further configured to couple a respective TC  44  to outer surface  55  at a predefined location. In some embodiments, a single patch  50  may be coupled to outer surface  55  along a latitudinal cut on the circumference of balloon assembly  40 , as shown in  FIG. 2 . 
     In other embodiments, balloon assembly  40  may comprise multiple patches  50  adapted to cover multiple respective openings (such as openings  48 ) formed in wall  54  as described above. 
     Note that openings  48  are typically formed at different respective locations than electrodes  42 . The distances between couples of a given TC  44  and its closest electrode  42  neighbor along outer surface  55 , may be uniform or may vary among different locations on outer surface  55 . 
     The leads for electrodes  42  (not shown) can be created in a similar manner as the thermocouple, except that the lead is left electrically exposed on the surface of the balloon and then electrode  42  is formed over the lead. Alternatively, the lead may be secured to the surface of the balloon with a conductive epoxy. The lead for electrode  42  may constitute a thermocouple where one wire is also used to deliver RF current and sense electrograms. 
       FIG. 3  is a flow chart that schematically illustrates a method for producing a balloon assembly of a catheter distal end, in accordance with an embodiment of the present invention. The method begins with coupling balloon assembly  40  to the jig, at a balloon coupling step  100 . In some embodiments, the jig is configured to set balloon assembly  40  to an expanded position. 
     At a sputtering process step  102 , electrodes  42  are sputtered on outer surface  55  of balloon assembly  40 , during a production process in which balloon assembly  40  is coupled to the jig. 
     In an embodiment, the jig (shown in  FIG. 4  below) may comprise a hollow mask assembly configured to contain balloon assembly  40  being fabricated. In an embodiment, the mask assembly may have one or more patterned openings through which, during the sputtering process, electrodes  42  are deposited on selected locations of assembly  40  that are exposed by the patterned openings. 
     In some embodiments, during sputtering process step  102 , which is typically carried out under environmental vacuum conditions in a sputtering process chamber (not shown), one or more electron beams or ion beams impinge on a typically metallic target so as to sputter atoms and/or ions from the target. 
     In an embodiment, the target is made from gold or from any other suitable material that will be deposited on balloon assembly  40 . In an embodiment, balloon assembly  40  is inflated, typically with an inert gas such as argon, before being inserted into the mask assembly. An operator mounts the mask assembly into the sputtering process chamber and pumps the air out of the process chamber so as to create a vacuum therein. 
     In some embodiments, there may be multiple targets made from gold, palladium, titanium-tungsten, silver, or other suitable metals to provide layers of metal to improve adhesion. 
     In a presence of vacuum, outer surface  55  of balloon assembly  40  inflates to press into an internal surface of the mask assembly. In this embodiment, the sputtered atoms pass through the patterned openings of the mask assembly and are deposited on balloon assembly  40  only at the intended locations on outer surface  55 , so as to form electrodes  42  thereon. 
     At an opening formation step  104 , one or more openings, such as opening  48 , are formed at given locations in wall  54  of balloon assembly  40 . In some embodiments, to produce the openings, wall  54  is cut along a single latitudinal of balloon assembly  40 , as shown in  FIG. 2  above. In other embodiments, any suitable shapes and number of cuts are formed in wall  54  by laser, heated needle, or mechanical means. 
     At a threading step  106 , leads  46  are threaded through opening  48 , such that TCs  44  and leads (not shown) for electrodes  42  are mounted on outer surface  55  of balloon assembly  40 . 
     In some embodiments, only leads  46  are threaded through opening  48 , and subsequently, each TC  44  is coupled to a respective lead  46 . In other embodiments, an assembly comprising TC  44  coupled to lead  46  is threaded through opening  48 . 
     At a patch placement step  108 , one or more patches, such as patch  50 , are cemented to the given locations on outer surface  55  of balloon assembly  40 , so as to couple respective TCs  44  at the predefined locations on outer surface  55 . In some embodiments, patches  50  are further configured to seal respective openings  48  so as to enable the inflation of balloon assembly  40 . 
     In some embodiments, a single patch  50  may be coupled to outer surface  55  along a latitudinal cut on the circumference of balloon assembly  40 , as shown in  FIG. 2  above. 
     In other embodiments, balloon assembly  40  may comprise multiple patches  50  adapted to cover multiple respective openings formed at the given locations in wall  54  as described above. 
     In some embodiments, patches  50  are configured to adhere to outer surface  55 , so as to block undesired exchange of fluids, through openings  48 , between the internal volume of assembly  40  and blood vessel  26 , or any other organ of patient  28 . Following step  108 , the method terminates. 
     In alternative embodiments, at least some of the steps of the method described above may be carried out in a different order. For example, sputtering process step  102  may be carried out after patch placement step  108 . 
       FIG. 4  is a schematic, sectional view of a balloon assembly  65  contained within a mask assembly  60 , in accordance with an embodiment of the present invention. Balloon assembly  65  may replace, for example, balloon assembly  40  of  FIG. 1  above. 
     In the example of  FIG. 4 , mask assembly  60  serves as a jig for producing balloon assembly  65 . In an embodiment, the configuration depicted in  FIG. 4  corresponds to sputtering process step  102  described in  FIG. 3  above. In some embodiments, mask assembly  60  has a substantially spherical shape and may comprise two detachable hemispheres  62  and  64 . In an embodiment, the hemispheres are detached from one another during the insertion of balloon assembly  65  into mask assembly  60 , and reattached to one another so as to contain assembly  40  therein. 
     In some embodiments, mask assembly  60  is made from metal, or any other suitable rigid material, which is adapted to withstand the vacuum applied during the sputtering process described in step  102 , without its shape being deformed. 
     In some embodiments, balloon assembly  65  is inflated (partially or fully), typically with an inert gas  80  such as argon, before being inserted into mask assembly  60 . In alternative embodiments, balloon assembly may be inflated after being inserted into mask assembly  60 , or using any other suitable inflating sequence. 
     In an embodiment, mask assembly  60  may comprise one or more intrusions  74  that correspond with protrusions  72  of balloon assembly  65 . Protrusions  72  and intrusions  74  may be used for aligning assemblies  65  and  60  to one another so as to enable accurate formation of electrodes  42  at their intended positions on assembly  65 . 
     For example, protrusions  72  of balloon assembly  65  may serve as inflating sleeves, which are sealed at their distal ends and are substantially narrower than the maximal diameter of assembly  65  when the balloon assembly is inflated to an expanded position. 
     In an embodiment, intrusions  74  may be located at upper pole  76  of hemisphere  62  and at lower pole  78  of hemisphere  64 . In this embodiment, protrusions  72  of assembly  65  fit into intrusions  74  of assembly  60 , thereby aligning assemblies  65  and  60  to one another. In other embodiment, any suitable alternative alignment technique may be used. 
     In some embodiments, assembly  65  may be inflated to a degree that leaves (after being inserted into assembly  60 ) a spacing  70  (filled with air) between assemblies  65  and  60 . In some embodiments, a production operator of assembly  65  may use spacing  70  to fine-tune the alignment between assemblies  65  and  60 . 
     In some embodiments, hemisphere  62  comprises one or more openings  68  patterned between bars  75 . Sputtering process step  102 , which is typically carried out in vacuum, causes the deformable external surface of balloon assembly  65  to attach to the internal surface of mask assembly  60 . 
     In an embodiment, assemblies  65  and  60  are attached to one another, so that the sputtered atoms pass through openings  68  of assembly  60  and are deposited on assembly  65  only at the intended positions on the external surface of assembly  65 , so as to form electrodes  42  thereon. 
     In the example of  FIG. 4 , hemisphere  64  has a solid profile (i.e., without openings) so that after sputtering process  102 , the external surface of assembly  65  that is located under bars  75  and under hemisphere  64 , is not coated with metal during sputtering process  102 . 
     In some embodiments, at opening formation step  104  of  FIG. 3  above, opening  48  may be formed in assembly  65  at the locations under bars  75  and/or under hemisphere  64 , which are not coated by the metal layer of electrodes  42 . Furthermore, patches  50  and TCs  44  may be coupled to the external surface of assembly  65  at location not coated with metal, such as the locations under bars  75  and/or under hemisphere  64 . 
     The examples of  FIGS. 1-4  refer to a specific configurations of balloon assemblies  40  and  65  and to a specific configuration of mask assembly  60 . These configurations, however, are chosen purely for the sake of conceptual clarity. In other embodiments, hemisphere  64  may have openings, and hemisphere  62  may have any suitable patterned openings, different than openings  68  shown in  FIG. 4 . 
     In alternative embodiments, the disclosed techniques can be used, mutatis mutandis, in various other types of distal end assemblies and balloon catheter. 
     Furthermore, the description of the jig is given purely by way of example. In alternative embodiments, balloon assemblies  40  and/or  65  may be coupled to any other suitable jig or mounted on any other type of manufacturing tool. 
     Although the embodiments described herein mainly address cardiology procedures, the methods and systems described herein can also be used in other applications, such as otolaryngology or neurology procedures. 
     It will thus be appreciated that the embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art. Documents incorporated by reference in the present patent application are to be considered an integral part of the application except that to the extent any terms are defined in these incorporated documents in a manner that conflicts with the definitions made explicitly or implicitly in the present specification, only the definitions in the present specification should be considered.