Abstract:
A catheter includes a proximal shaft and a distal shaft having differing diameters; often, the distal shaft will have a smaller diameter than the proximal shaft. A coupling joins the distal shaft to the proximal shaft. For example, a proximal portion of the distal shaft can be inserted into the coupling through its distal end, while the proximal portion of the coupling can be inserted into the proximal shaft through its distal end. To provide an atraumatic transition from the distal shaft to the proximal shaft, coupling can taper towards its distal end, for example by using a dome- or frustoconical-shape for the distal portion of the coupling. The exterior of the coupling can be ribbed to facilitate bonding to the proximal shaft. The distal shaft can be formed into at least a partial loop having a fixed or variable radius of curvature.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application No. 62/280,159, filed 19 Jan. 2016, which is hereby incorporated by reference as though fully set forth herein. 
     
    
     BACKGROUND 
       [0002]    The instant disclosure relates to catheters for use in medical procedures, such as electrophysiology studies. In particular, the instant disclosure relates to an atraumatic coupling that can be used to join two shafts of unequal size. 
         [0003]    Catheters are used for an ever-growing number of procedures, such as diagnostic, therapeutic, and ablative procedures, to name just a few examples. Typically, the catheter is manipulated through the patient&#39;s vasculature and to the intended site, for example, a site within the patient&#39;s heart. 
         [0004]    A typical electrophysiology catheter includes an elongate shaft and one or more electrodes on the distal end of the shaft. The electrodes may be used for ablation, diagnosis, or the like. Oftentimes, these electrodes are ring electrodes that extend about the entire circumference of the catheter shaft. 
         [0005]    One specific use of an electrophysiology catheter is to map the atrial regions of the heart, and in particular the pulmonary veins, which are often origination points or foci of atrial fibrillation. Such electrophysiology mapping catheters typically have at least a partial loop shape at their distal end, oriented in a plane generally orthogonal to the longitudinal axis of the catheter shaft, which allows the loop to surround the pulmonary vein ostia. 
         [0006]    Further, the more proximal and elongate region of the shaft often has a larger diameter than the more distal region (e.g., the portion formed into at least a partial loop). Thus, there is a need to transition from the larger diameter proximal shaft to the smaller diameter distal shaft. 
       BRIEF SUMMARY 
       [0007]    Disclosed herein is a catheter including: a proximal shaft having a first diameter; a distal shaft having a second diameter different from the first diameter; and a coupling joining the proximal shaft to the distal shaft, the coupling having a hollow interior and including a distal portion and a proximal portion, wherein a proximal portion of the distal shaft is inserted into the hollow interior of the coupling through a distal end of the coupling and the proximal portion of the coupling is inserted into the proximal shaft through a distal end of the proximal shaft. 
         [0008]    In embodiments, the catheter also includes a sensor having a hollow core disposed within a distal portion of the proximal shaft, wherein the proximal portion of the coupling is inserted into the hollow core of the sensor and the distal portion of the proximal shaft. The proximal portion of the coupling can include a first sub-portion having an outer diameter small enough to allow insertion into the hollow core of the sensor; and a second sub-portion having an outer diameter small enough for insertion into the distal portion of the proximal shaft, but too large for insertion into the hollow core of the sensor, wherein the second sub-portion is positioned distally of the first sub-portion. 
         [0009]    According to aspects of the disclosure, an outer diameter of the coupling is smaller at the distal end of the coupling than at a point adjacent the distal end of the proximal shaft. For example, the distal portion of the coupling comprises can include dome shaped portion and/or a frustoconical portion. 
         [0010]    According to other aspects of the disclosure, a maximum outer diameter of the proximal portion of the coupling is less than a maximum outer diameter of the distal portion of the coupling. 
         [0011]    The hollow interior of the coupling can include an abutment surface for the proximal portion of the distal shaft, which stops the advancement of the distal shaft into the coupling at a desired depth. It is also contemplated that the coupling can cause the distal shaft to be positioned coaxially within the proximal shaft. 
         [0012]    In embodiments, an exterior surface of the coupling includes a plurality of ribs. The coupling can also be made out of a clear polymeric material, for example to facilitate visualization of the distal shaft within the coupling. 
         [0013]    The distal shaft can be formed into at least a partial loop. The radius of curvature of the loop can be fixed or variable. 
         [0014]    Also disclosed herein is a method of manufacturing a catheter, including: providing a proximal shaft having a first diameter, a distal shaft having a second diameter different from the first diameter, and a coupling having a hollow interior; inserting a proximal portion of the distal shaft into the hollow interior of the coupling through a distal end of the coupling; inserting a proximal portion of the coupling into the proximal shaft through a distal end of the proximal shaft; securing the distal shaft to the coupling; and securing the proximal shaft to the coupling. 
         [0015]    The hollow interior of the coupling can include an inner abutment surface, such that inserting a proximal portion of the distal shaft into the hollow interior of the coupling through a distal end of the coupling can include advancing the proximal portion of the distal shaft into the hollow interior of the coupling until a proximal end of the distal shaft abuts the inner abutment surface. Similarly, an exterior surface of the coupling can include an outer abutment surface, such that inserting a proximal portion of the coupling into the proximal shaft through a distal end of the proximal shaft can include advancing the proximal portion of the coupling into the proximal shaft until the distal end of the proximal shaft abuts the outer abutment surface. 
         [0016]    According to aspects of the disclosure, the manufacturing method also includes: providing a sensor having a hollow core; inserting the proximal portion of the coupling into the hollow core of the sensor; and inserting the proximal portion of the coupling and the sensor into the proximal shaft through the distal end of the proximal shaft. 
         [0017]    The distal shaft, coupling, and proximal shaft can be secured to each other, for example, using an ultraviolet curing adhesive. 
         [0018]    In another aspect, the present disclosure provides an atraumatic coupling for securing a first shaft segment to a second shaft segment having a different outer diameter from the first shaft segment. The coupling includes: a proximal portion having an exterior surface, the exterior surface of the proximal portion including a plurality of ribs, and wherein an outer diameter of the proximal portion is not greater than an inner diameter of the first shaft segment; and a distal portion, the distal portion having an exterior surface that tapers from a point at which the proximal portion meets the distal portion to a distal tip of the distal portion, and wherein an outer diameter of the distal portion at the point at which the proximal portion meets the distal portion is about equal to an outer diameter of the first shaft segment, wherein at least the distal portion defines an interior cavity of the coupling, and wherein a diameter of the interior cavity of the coupling is not smaller than an outer diameter of the second shaft segment. It is contemplated that the coupling can include a clear polymeric material. 
         [0019]    The foregoing and other aspects, features, details, utilities, and advantages of the present invention will be apparent from reading the following description and claims, and from reviewing the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIGS. 1 and 2  illustrate exemplary electrophysiology catheters. 
           [0021]      FIG. 3  is a close up of a portion of an electrophysiology catheter according to some embodiments of the instant disclosure. 
           [0022]      FIG. 4  depicts the assembly of a distal shaft, a proximal shaft, a coupling, and a sensor according to aspects of the disclosure. 
           [0023]      FIG. 5A  is a perspective view of an embodiment of a coupling as disclosed herein. 
           [0024]      FIG. 5B  is a cross-sectional view of the coupling of  FIG. 5A . 
           [0025]      FIG. 6  is a simplified cross-sectional assembly drawing of a distal shaft, a proximal shaft, a coupling, and a sensor as disclosed herein. 
           [0026]      FIG. 7  is a cross-sectional view of another embodiment of a coupling as disclosed herein. 
           [0027]      FIG. 8  is a perspective view of still another embodiment of a coupling as disclosed herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    For the sake of illustration, certain embodiments of the disclosure will be explained herein with reference to an electrophysiology catheter utilized in cardiac electrophysiology studies. It should be understood, however, that the present teachings may be applied to good advantage in other contexts as well. 
         [0029]    Referring now to the figures,  FIGS. 1 and 2  depict two embodiments of an electrophysiology (“EP”) catheter  10  according to aspects of the present disclosure. EP catheter  10  includes catheter body  12 , which in turn includes a proximal shaft  14 , a distal shaft  16 , and a coupling  18  that joins proximal shaft  14  and distal shaft  16  as discussed herein. In some embodiments, catheter body  12  is tubular (e.g., it defines at least one lumen therethrough). It should also be understood that the relative lengths of proximal shaft  14 , distal shaft  16 , and coupling  18  as depicted in  FIGS. 1 and 2  are merely illustrative and may vary without departing from the spirit and scope of the instant disclosure. Of course, the overall length of catheter body  12  should be long enough to reach the intended destination within the patient&#39;s body. 
         [0030]    Catheter body  12  will typically be made of a biocompatible polymeric material, such as polytetrafluoroethylene (PTFE) tubing (e.g., TEFLON® brand tubing). Of course, other polymeric materials, such as fluorinated ethylene-propylene copolymer (FEP), perfluoroalkoxyethylene (PFA), poly(vinylidene fluoride), poly(ethylene-co-tetrafluoroethylene), and other fluoropolymers, may be utilized. Additional suitable materials for catheter body  12  include, without limitation, polyamide-based thermoplastic elastomers (namely poly(ether-block-amide), such as PEBAX®), polyester-based thermoplastic elastomers (e.g., HYTREL®), thermoplastic polyurethanes (e.g., PELLETHANE®, ESTANE®), ionic thermoplastic elastomers, functionalized thermoplastic olefins, and any combinations thereof. In general, suitable materials for catheter body  12  may also be selected from various thermoplastics, including, without limitation, polyamides, polyurethanes, polyesters, functionalized polyolefins, polycarbonate, polysulfones, polyimides, polyketones, liquid crystal polymers and any combination thereof. It is also contemplated that the durometer of catheter body  12  may vary along its length. In general, the basic construction of catheter body  12  will be familiar to those of ordinary skill in the art, and thus will not be discussed in further detail herein except to the extent necessary to understand the instant disclosure. 
         [0031]    As seen in  FIG. 3 , distal shaft  16  can be predisposed into at least a partial loop. This loop shape allows distal shaft  16  to conform to the shape, for example, of a pulmonary vein ostium. The partial loop may take a number of configurations, depending on the intended or desired use of EP catheter  10 , consistent with the present teachings. Therefore, it should be understood that the loop configuration depicted in  FIG. 3  is merely illustrative. 
         [0032]      FIG. 3  also illustrates that distal region  16  can include a plurality of electrodes  20  disposed thereon. Electrodes  20  may be ring electrodes or any other electrodes suitable for a particular application of EP catheter  10 . For example, where EP catheter  10  is intended for use in a contactless electrophysiology study, electrodes  20  may be configured as described in U.S. application Ser. No. 12/496,855, filed 2 Jul. 2009, which is hereby incorporated by reference as though fully set forth herein. Of course, in addition to serving sensing purposes (e.g., cardiac mapping and/or diagnosis), electrodes  20  may be employed for therapeutic purposes (e.g., cardiac ablation and/or pacing). 
         [0033]      FIG. 3  further illustrates that the outer diameter of proximal shaft  14  differs from the outer diameter of distal shaft  16 . For example, the outer diameter of proximal shaft  14  can be 8 French (0.104 inches), while the outer diameter of distal shaft  16  can be 4 French (0.052 inches). Thus, coupling  18  secures proximal shaft  14  to distal shaft  16  while providing an atraumatic transition from the outer diameter of one to the outer diameter of the other as discussed in further detail below. This is also illustrated to good advantage in  FIG. 4 . 
         [0034]    Referring again to  FIGS. 1 and 2 , a handle  22  is coupled to catheter body  12 . Handle  22  includes suitable actuators (e.g., actuator  24   a  in  FIG. 1 ; actuator  24   b  in  FIG. 2 ) to control the deflection of catheter body  12 , for example as described in U.S. Pat. No. 8,369,923, which is hereby incorporated by reference as though fully set forth herein. Various handles and their associated actuators for use in connection with electrophysiology catheters are known, and thus handle  22  will not be described in further detail herein. 
         [0035]    Although in some embodiments, the radius of curvature of the loop of distal shaft  16  may be fixed, it is also contemplated that it may be adjustable, for example to conform to the varying sizes of pulmonary vein ostia of patients of different ages. This additional control may be provided, for example, via the use of an activation wire that is adapted to alter the radius of curvature of the loop of distal shaft  16 . One suitable material for such an activation wire is stainless steel, though other materials can be employed without departing from the spirit and scope of the instant disclosure. 
         [0036]    In some embodiments, one end (e.g., the distal end) of the activation wire may be coupled to the tip of catheter body  12  (e.g., coupled to a distal-most tip electrode of electrodes  20 ), while the other end (e.g., the proximal end) of the activation wire may be coupled to an actuator (e.g., a thumb slider) on handle  22 . Thus, for example, sliding the thumb slider proximally can place the activation wire in tension, thereby altering the radius of curvature of the loop of distal shaft  16 . 
         [0037]    Another exemplary mechanism for varying the radius of curvature of the loop of distal shaft  16  is described in U.S. Pat. No. 7,606,609, which is hereby incorporated by reference as though fully set forth herein. 
         [0038]    A first embodiment of coupling  18  is depicted in perspective view in  FIG. 5A  and in cross-section in  FIG. 5B . As shown in  FIGS. 5A and 5B , coupling  18  includes a hollow interior  28 . As used herein, the term “hollow interior” means that there is at least one cavity within the interior; the term “hollow core” is used synonymously in this disclosure. Although this cavity is depicted in  FIGS. 5A and 5B  as extending throughout the entire length of coupling  18  with a substantially constant diameter, the term “hollow” is not intended to be so limited. Thus, the diameter of the cavity can vary along the length of coupling  18  and still be considered “hollow” within the meaning of the instant disclosure. 
         [0039]    Coupling  18  includes a distal portion  30  and a proximal portion  32 . As shown in the simplified assembly drawing of  FIG. 6 , distal portion  30  of coupling  18  receives distal shaft  16  (e.g., the proximal portion  34  of distal shaft  16  is inserted into hollow interior  28  of coupling  18  through the distal end  36  of coupling  18 ). Similarly, proximal portion  32  of coupling  18  is received into proximal shaft  14  (e.g., proximal portion  32  of coupling  18  is inserted into proximal shaft  14  through the distal end  38  of proximal shaft  14 ). 
         [0040]      FIGS. 5A, 5B, and 6  also illustrate that the outer diameter of coupling  18  changes along its length. In particular, the outer diameter of coupling  18  is narrower at its distal end  36  than it is at a point adjacent distal end  38  of proximal shaft  14 . That is, distal portion  30  of coupling  18  tapers towards its distal end  36  and can, in embodiments, include a dome-shape as shown in  FIGS. 5A, 5B, and 6 . In other embodiments, such as shown in  FIG. 7 , distal portion  30  of coupling  18  can include a frustoconical shape. 
         [0041]    According to aspects of the disclosure, the maximum outer diameter of proximal portion  32  of coupling  18  is less than the maximum outer diameter of distal portion  30  of coupling  18 . It is further contemplated that the outer diameter of the distal portion  30  of coupling  18  where distal portion  30  meets proximal portion  32  (e.g., a point adjacent distal end  38  of proximal shaft  14  when catheter  10  is assembled) is about equal to the outer diameter of proximal shaft  14  in order to facilitate a smooth transition to proximal shaft  14 . Thus, for example, if proximal shaft  14  has an 8 French outer diameter, then the outer diameter of coupling  18  where distal portion  30  thereof transitions to proximal portion thereof can also be about 8 French. There can, however, be about an 8% difference in these outer diameters without adversely affecting the smooth and atraumatic transition provided by the combination of the tapering shape of distal portion  30  and the relative diameters of distal portion  30 , proximal portion  32 , and proximal shaft  14  (e.g., as shown in  FIG. 4 ). 
         [0042]    As shown in  FIGS. 6 and 7 , proximal portion  32  of coupling  18  can include an abutment surface  40 . Abutment surface  40  stops the advancement of distal shaft  16  into hollow interior  28  of coupling  18 . That is, distal shaft  16  is advanced into hollow interior  28  of coupling  18  until the proximal portion  34  of distal shaft  16  abuts the abutment surface  40  (see  FIG. 6 ). 
         [0043]    The exterior surface of proximal portion  32  of coupling  18  can also include one or more ribs  42 . Ribs  42  can increase the bondability between coupling  18  and proximal shaft  14 , for example by creating a mechanical lock with the adhesive used to attach coupling  18  to proximal shaft  14 . 
         [0044]      FIG. 8  depicts an additional embodiment of coupling  18  that is configured to facilitate the positioning of an additional sensor  44  (shown in  FIGS. 4 and 6 ) along catheter body  12 . In the embodiment of coupling  18  depicted in  FIG. 8 , proximal portion  32  of coupling  18  includes a first sub-portion  46  and a second sub-portion  48 . First sub-portion  46  has an outer diameter small enough for insertion into a hollow core of sensor  44  such that, for example, sensor  44  is advanced until it abuts surface  50  at the transition between first and second sub-portions  46 ,  48  (which can be the opposite side of abutment surface  40  against which distal shaft  16  abuts). 
         [0045]    Second sub-portion  48 , which is distal of first sub-portion  46 , has an outer diameter small enough for insertion into proximal shaft  14 , but too large for insertion into the hollow core of sensor  44 . Second sub-portion  48  (and thus proximal portion  32 ) ends at surface  52 , which restricts the advancement of coupling  18  into proximal shaft  14  during assembly. 
         [0046]    Alternatively, coupling  18  can also serve as a datum for positioning one or more sensors  44  without having coupling  18  inserted therein. 
         [0047]    In embodiments, coupling  18  can be made of a clear polymeric material. The use of a clear polymeric material enables the use of an ultraviolet curing adhesive to join coupling  18  to distal shaft  16 . It also facilitates visual confirmation that distal shaft  16  is properly positioned within coupling  18 . Of course, in other embodiments, coupling  18  can be translucent or opaque. 
         [0048]    Assembly of catheter body  12  can be understood with reference to  FIG. 6 . Distal shaft  16  is inserted into hollow interior  28  of coupling  18  through the distal end  36  of coupling  18  until proximal portion  34  of distal shaft  16  reaches the abutment surface  40  within proximal portion  32  of coupling  18 . 
         [0049]    Optionally, a hollow core sensor  44  can be fit over first sub-portion  46  of proximal portion  32  of coupling  18 , for example until sensor  44  abuts surface  50 . Proximal portion  32  of coupling  18  (and sensor  44 , if present) can then be inserted into proximal shaft  14  through distal end  38  of proximal shaft  14 , for example until distal end  38  of proximal shaft  14  abuts surface  52 . 
         [0050]    Advantageously, coupling  18  facilitates coaxial alignment between proximal shaft  14 , sensor  44  (if present), and distal shaft  16 . Once the desired alignment is achieved, the various components can be secured to one another, for example via the use of an ultraviolet curing adhesive. 
         [0051]    Although several embodiments of this invention have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention. 
         [0052]    For example, although certain exemplary embodiments have been described above with reference to a unitary coupling  18 , it is contemplated that coupling  18  can also include multiple constituent parts that are mated together during assembly of catheter  10 . 
         [0053]    All directional references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader&#39;s understanding of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the invention. Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. 
         [0054]    It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims.