Abstract:
A method of bonding a first tubular member to a second tubular member to form a catheter shaft. The method comprising the step of providing a first tubular member including a distal end, a proximal end, and a lumen extending between the distal end and the proximal end thereof. The method further including the step of providing a second tubular member including a distal end, a proximal end, and a lumen extending between the distal end and the proximal end thereof. The method further including the steps of inserting a joining portion of the first tubular member into a joining portion of the second tubular member and applying heat the joining portions.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to catheters for performing medical procedures. More particularly, the present invention relates to guide catheters for use in angioplasty procedures. 
     BACKGROUND OF THE INVENTION 
     Intravascular diseases are commonly treated by relatively non-invasive techniques such as percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA). These angioplasty techniques typically involve the use of a balloon catheter. In these procedures, a balloon catheter is advanced through the vasculature of a patient such that the balloon is positioned proximate a restriction in a diseased vessel. The balloon is then inflated and the restriction in the vessel is opened. 
     The most widely used form of angioplasty makes use of a guide catheter positioned within the vascular system of a patient. The guide catheter assists in transporting the balloon dilation catheter to the restriction in the diseased vessel. During this procedure, the distal end of the guide catheter is typically inserted into the femoral artery located near the groin of the patient. The guide catheter is urged through the vasculature of the patient until its distal end is proximate the restriction. In many cases, the distal end of the guide catheter is positioned in the ostium of the coronary artery. The balloon catheter may then be fed through a lumen in the guide catheter. 
     It is desirable that a guide catheter incorporate a level of rigidity which will allow it to be passed through the vascular system without folding or buckling. To assist in directing the distal tip of the guide catheter to the coronary ostium of the patient, the distal portion of the guide catheter may include one or more bends. The distal tip of the guide catheter is typically formed from relatively soft, flexible material to avoid trauma to arterial vessels, and allow flexing of the distal tip to aid the guide catheter in traversing desired arterial branches. 
     In some applications, it is desirable to form a guide catheter by bonding together two or more tubular sections in order to achieve a more rigid proximal portion and more flexible distal portion. It may also be desirable to have the distal portion of the guide catheter shaft be comprised of one or more tubular sections which are adapted to be formed into a curved shape. As described above, these curves aid in directing the distal tip of the guide catheter to the coronary ostium of a patient. In some embodiments, it is desirable to have a distal portion of the elongate shaft which can be heated and bent to a desired shape, then allowed to cool. By way of a second example, it may be desirable to include one or more tubular sections having a reinforcement braid, and one or more additional tubular sections having no braid. A braid or other reinforcement member is used to strengthen the tubular section and increase torque transmission. When a guide catheter is comprised of more than one generally tubular section, these sections are joined together at joints where the distal end of a first tubular section is affixed to the proximal end of a second tubular section. 
     SUMMARY OF THE INVENTION 
     The present invention relates generally to catheters for performing medical procedures. More particularly, the present invention relates to guide catheters for use in an angioplasty procedure. A guide catheter in accordance with the present invention includes an elongate shaft. A hub may be affixed to the proximal end of the elongate shaft and an atraumatic tip may be affixed to the distal end of the elongate shaft. The elongate shaft is preferably comprised of more than one generally tubular section. 
     A method of bonding tubular members in accordance with the present invention may begin with the step of forming a joining region on the distal portion of a first tubular member. The joining region preferably includes a plurality of ribs and a plurality of areas with a generally reduced diameter relative to the ribs. A variety of manufacturing methods may be used to form the ribs including material forming processes and material removal processes. 
     A method in accordance with the present invention includes the step of positioning a mandrel. so that at least a portion of its length is disposed inside the lumen of the first tubular member. The joining region of the first tubular member is then inserted into the lumen of a second tubular member. After the joining region of the first tubular member is inserted into the lumen of the second tubular member, the mandrel will be positioned so that at least a portion of the length thereof is disposed inside both the lumen of the first tubular member and the lumen of the second tubular member. 
     The assembled tubular members are then subjected to heat and pressure proximate the joining region of the first tubular member. A number of methods may be used to heat the tubular members, including convection, conduction and radiation. The second tubular member is thus bonded to the first tubular member at the joining region. 
     Having formed a bond, the assembly is then allowed to cool. The assembly may be submersed in a relatively cool fluid to speed cooling of the assembly. Examples of fluids which may be suitable for some applications include water and air. Relatively cool air may also be impinged onto the assembly. After the catheter assembly has cooled, the mandrel may be removed from the lumen of the catheter assembly. 
     An additional method in accordance with the present invention includes the step of positioning a shrink wrap sleeve over both tubular members in an area proximate the joining region of the first tubular member. After the sleeve is disposed about the tubular members, heat is applied to joining regions to form a bond. At an elevated temperature, the shrink wrap sleeve applies the pressure necessary to form the second tubular member around the joining region of the first tubular member. Having formed a bond, the assembly is then allowed to cool. After the assembly has cooled, the sleeve and the mandrel are removed. 
     An additional method in accordance with the present invention may be used to bond a hub to a tubular member. This method typically begins with the step of forming a bonding region on the tubular member proximate the proximal end thereof. The bonding region typically includes at least one rib and at least one area of generally reduced diameter relative to the rib diameter. The proximal portion of the tubular member is then positioned inside the cavity of a molding tool. Molten plastic is then injected into the cavity of the molding tool and allowed to cool. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a guide catheter in accordance with an exemplary embodiment of the present invention; 
     FIG. 2 is a sectional plan view of a tubular member having a joining region form thereon depicting raised ribs and reduced diameter portions therebetween; 
     FIG. 3 is an enlarged partial sectional view of a rib portion on a catheter shaft; 
     FIG. 4 is a sectional plan view of the tubular member of FIG. 2 with a second tubular member disposed over the joining region prior to bonding; 
     FIG. 5 is a sectional plan view of a first tubular member which has been bonded to a second tubular member depicting the second tubular member conforming to the ribs and reduced diameter portions therebetween; 
     FIG. 6 is a sectional plan view of the tubular member of FIG. 2 with a second tubular member disposed over the joining region and a heat shrink sleeve disposed over the assembly prior to bonding; and 
     FIG. 7 is a plan view of a hub assembly in accordance with an exemplary embodiment of the present invention incorporating ribs and reduced diameter portions on a joining region. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description should be read with reference to the drawings, in which like elements in different drawings are numbered identically. The drawings, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. 
     Examples of construction, materials, dimensions, and manufacturing processes are provided for selected elements. All other elements employ that which is known to those of skill in the field of the invention. Those skilled in the art will recognize that many of the examples provided have suitable alternatives which may be utilized. 
     FIG. 1 is a plan view of a guiding catheter  10 . Guiding catheter  10  includes an elongate shaft  12 , a distal portion  14 , and a proximal portion  16 . Proximal portion  16  of catheter  10  includes a hub  30  and a strain relief  32 . Hub  30  and strain relief  32  enable a physician to connect other devices to guiding catheter  10 . Hub  30  and strain relief  32  also provide a convenient place for a physician to apply longitudinal or rotational forces in order to manipulate guiding catheter  10 . Connected to the distal end of catheter  10  is a distal tip  20 . In a preferred embodiment, distal tip  20  is generally softer and more flexible than elongate shaft  12 . 
     Those of skill in the art will appreciate that for many applications of catheter  10 , elongate shaft  12  is preferably comprised of more than one generally tubular section  50 . For example, the distal portion of elongate shaft  12  may be comprised of one or more tubular sections  50  which are adapted to be formed into a curved shape. Curves disposed proximate the distal portion of elongate shaft  12  aid in directing the distal end of catheter  10  to the coronary ostium of a patient. In some embodiments, it is desirable to have a distal portion of elongate shaft  12  which can be heated and bent to a desired shape, then allowed to cool. By way of a second example, it may be desirable to include one or more tubular sections  50  having a reinforcement braid, and one or more additional tubular sections  50  having no braid. When elongate shaft  12  is comprised of more than one generally tubular section  50 , these sections are joined together at joints where the distal end of a first tubular section  50  is affixed to the proximal end of a second tubular section  50 . FIG. 2 is an enlarged sectional view of a preferred distal portion  14  of a tubular section  50  of the present invention having a joining region  52  and a lumen  48 . Tubular section  50  is comprised of an inner tube  54  which is overlaid by a support member  56 . An outer tube  58  overlays support member  56  and preferably terminates proximal to thejoining region  52 . Joining region  52  of tubular section  50  includes a plurality of ribs  60  extending circumferentially around the shaft at spaced longitudinal positions. The joining region  52 , including the ribs  60  and axial spaces therebetween, preferably has a smaller outside diameter than the shaft proximal thereto. The ribs have a slightly larger diameter than the axial regions therebetween. 
     A variety of manufacturing methods may be used to form joining region  52  and ribs  60  of tubular section  50  including material forming processes and material removal processes. Examples of material removal processes which may be acceptable in some applications include turning on a lathe and centerless grinding. An example of a material forming process which may be acceptable in some applications is forging by compressing joining region  52  of tubular section  50  in a heated tool of the desired shape. 
     In a preferred embodiment, inner tube  54  is comprised of PTFE (polytetrafluoroethylene). PTFE is a preferred material because it creates a smooth, low-friction surface for the passage of other devices through the catheter. Also in a preferred embodiment, support member  56  is a stainless steel wire, wound in a braided pattern around inner tube  54 . Those with skill in the art will appreciate that other embodiments of support member  56  are possible without deviating from the spirit and scope of the present invention. For example, support member  56  may be comprised of a woven polymer fabric. By way of a second example, support member  56  may be comprised of polymer fibers wound in a braided pattern. 
     In a preferred embodiment, outer tube  58  is comprised of polyether block amide (PEBA). Polyether block amide is commercially available from Atochem Polymers of Birdsboro, Pa. under the trade name PEBAX. Outer tube  58  may be fabricated using an extrusion process. In this process, molten PEBA is extruded onto the combined layers of inner tube  54  and support member  56 . When this process is used, the material of outer tube  58  fills any interstitial spaces in support member  56 . 
     It is to be understood that other manufacturing processes can be used without departing from the spirit and scope of the present invention. Outer tube  58  may also be comprised of other materials without departing from the spirit of scope of this invention. Examples of materials which may be suitable in some applications include: polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polyurethane, and polytetrafluoroethylene (PTFE). 
     As described previously, the material of distal tip  20  is preferably a relatively soft material. Distal tip  20  may be comprised of a material which is softer than the material of outer layer  56 . In a preferred embodiment, both distal tip  20  and outer layer  56  are comprised of polyether block amide (PEBA). However, in this preferred embodiment, distal tip  20  is comprised of a PEBA material with a lower durometer than that of outer layer  56 . 
     Those with skill in the art will appreciate that other embodiments of tubular section  50  are possible without deviating from the spirit or scope of the present invention. For example, tubular section  50  may include more or fewer component layers. 
     FIG. 3 is an enlarged sectional view of an additional embodiment of a tubular section  50 . In the embodiment of FIG. 3, tubular section  50  includes a wall  250  which is comprised of a first material. Tubular section  50  also includes a joining region  52  having a plurality of ribs  60 . A variety of manufacturing methods may be used to form ribs  60  on joining region  52  of tubular section  50  including material forming processes and material removal processes. Examples of material removal processes which may be acceptable in some applications include turning on a lathe and centerless grinding. An example of a material forming process which may be acceptable in some applications is forging by compressing joining region  52  of tubular section  50  in a heated tool of the desired shape. Ribs  60  are preferably about 0.001 inches to about 0.006 inches in height relative to the reduced diameter longitudinal regions therebetween. 
     FIG. 4 is a plan view of an assembly including a first tubular member  50  and a second tubular member  51 . Tubular members  50  and  51  include lumens  48  and  49 , respectively. In FIG. 4, a mandrel  100  has been positioned so that at least a portion of its length is disposed inside lumens  48 ,  49  of tubular members  50 ,  51 . Tubular member  50  includes bonding region  52  having a plurality of ribs  60 . Tubular member  51  includes a joining region  53 , which is a portion of the lumen wall over a selected length. 
     In FIG. 4, bonding region  52  of tubular member  50  has been inserted into bonding region  53  of tubular member  51 . In a preferred embodiment of tubular member  51 , the inner diameter of bonding region  53  is slightly flared to facilitate the insertion of bonding region  52  of tubular member  50 . This flared diameter may be created using a heat forming process. Alternately, bonding region  52  of tubular member  50  may be press fit into bonding region  53  of tubular member  51  without first creating a flare. 
     A method of bonding tubular members in accordance with the present embodiment may be described making reference to FIG. 4. A preferred method begins with the step of forming joining region  52  and ribs  60  in tubular member  50 . A variety of manufacturing methods may be used to form ribs  60  on tubular member  50  including material forming processes and material removal processes. Examples of material removal processes which may be acceptable in some applications include turning on a lathe and centerless grinding. An example of a material forming process which may be acceptable in some applications is forging by compressing joining region  52  of tubular member  50  in a heated tool of the desired shape. 
     A method in accordance with the present invention includes the step of positioning mandrel  100  so that at least a portion of its length is disposed inside lumen  48  of tubular member  50 . In a preferred method, this step takes place after the formation of joining region  52  and ribs  60 . Those of skill in the art will appreciate that the order of the steps in this method may be changed without deviating from the spirit and scope of the invention. For example, mandrel  100  may be positioned in lumen  48  of tubular member  50  prior to the formation of joining region  52  and ribs  60 . Alternately, mandrel  100  may be positioned in lumen  48  of tubular member  50  after joining region  52  of tubular member  50  has been inserted into joining region  53  of tubular member  51 . 
     In the next step of a preferred method, bonding region  52  of tubular member  50  is inserted into bonding region  53  of tubular member  51 . A preferred method in accordance with the invention includes the step of flaring the inner diameter of tubular member  51  proximate bonding region  53 . Bonding region  53  of tubular member  51  may be flared to facilitate the insertion of bonding region  52  of tubular member  50 . A number of methods may be used to flare tubular member  51  proximate bonding region  53 . In a method which may be suitable for some applications, the bonding region  53  of tubular member  51  is heated, then a mandrel is urged into lumen  49  of tubular member  51 . To facilitate the flaring process, a portion of the mandrel has a diameter larger than the diameter of lumen  49  of tubular member  51 . It should be noted that the mandrel may include steps and tapers. The distal end of tubular member  51  takes on the shape of the mandrel as a result of urging the mandrel into heated tubular member  51 . 
     After bonding region  52  of tubular member  50  is inserted into bonding region  53  of tubular member  51 , mandrel  100  will be positioned so that at least a portion of the length thereof is disposed inside both lumen  48  of tubular member  50  and lumen  49  of tubular member  51 . 
     Having thus assembled tubular members  50 ,  51 , heat and pressure are applied to joining regions  52 ,  53 . A number of methods may be used to heat joining regions  52 ,  53  including convection, conduction and radiation. An example of heating with radiant energy is directing infrared energy from an infrared heat source at joining regions  52  and  53 . Infrared energy sources suitable for this process are commercially available from Research Incorporated of Minnetonka, Minn. A second example of heating with radiant energy is exposing the regions to be heated to radio frequency energy. 
     An example of heating with convection includes directing a flow of hot air from a hot air gun so that it impinges on joining regions  52  and  53 . Hot air guns suitable for this application are commercially available from Leister Elektro-Geratebau of Lucerne, Switzerland. A second example of heating with convection includes placing the portion being heated in a temperature chamber. Temperature chambers suitable for this process are commercially available from Thermotron Corporation of New Holland, Mich. 
     An example of heating with conduction is placing a heated tool in direct contact with the outside diameter of joining region  53  and/or the inside diameter of joining region  52 . Suitable heated tools may be comprised of a number of materials including stainless steel. Electric heaters suitable for heating a heated tool are commercially available from Watlow Incorporated of St. Louis, Mo. 
     Pressure may be applied to joining regions  52 ,  53  via a fluid under pressure or via a solid tool adapted to apply pressure to the outer diameter of joining region  53 . Pressure may be applied using a fluid by positioning joining regions  52 ,  53  within a pressure vessel, then pressurizing the vessel with a fluid. In this example, the fluid could be air, water, alcohol, nitrogen gas, etc. 
     Having formed a bond, the assembly is then allowed to cool. The assembly may be submersed in a relatively cool fluid to speed cooling of the assembly. Examples of fluids which may be suitable for some applications include water and air. Relatively cool air may also be impinged onto the assembly. Cold air generators suitable for this purpose are commercially available from ITW Vortec of Cincinnati, Ohio and Exair Corporation of Cincinnati, Ohio. 
     After the catheter assembly has cooled, mandrel  100  may be removed from the lumen of the catheter assembly. In a preferred method, the outer surface of mandrel  100  includes polytetrafluoroethylene (PTFE). PTFE is preferred because it provides a substantially non-stick surface. This substantially non-stick surface aids in the removal of mandrel  100  from the lumen of the catheter assembly. 
     FIG. 5 is a partial plan view illustrating joining regions  52 ,  53  after the completion of the bonding process. In FIG. 5 tubular member  51  is shown in cross-section and tubular member  50  is not. As seen in FIG. 5, the material of tubular member  51  has conformed to the shape of bonding area  52  of tubular member  50 . As a result of the joining process, joining region  53  of tubular member  51  includes a groove  62  corresponding to each rib  60  of tubular member  50 . The interlocking geometry of ribs  60  and grooves  62  increases the mechanical strength of the resulting joint. Also as a result of the joining process, a lap joint heat bond  70  has been formed between the inner diameter of tubular member  51  and the outer diameter of tubular member  50 . Also as a result of the joining process, a butt joint heat bond  72  has been formed between the proximal end of tubular member  51  and the distal end of tubular member  50 . 
     An additional method in accordance with the present invention is illustrated in FIG.  6 . This method includes the step of positioning a sleeve  120  over both tubular members  50 ,  51  in an area proximate joining area  53 . In a preferred embodiment, sleeve  120  is comprised of heat shrinkable polytetrafluoroethylene (PTFE). PTFE is preferred because it provides a substantially non-stick surface. 
     In a preferred embodiment, sleeve  120  is comprised of PTFE heat shrink tubing. Suitable PTFE heat shrink tubing is commercially available from Zeus Industries of Orangeburg, S.C. and Raychem Corporation of Menlo Park, Calif. When sleeve  120  is comprised of shrink tubing, the step of shrinking sleeve  120  may be included in a method in accordance with the present invention. A number of methods may be used to shrink sleeve  120  without departing from the spirit and scope of the present invention, including those steps previously described in conjunction with FIG.  5 . In a preferred method, hot air is first impinged upon sleeve  120  causing it to shrink. Hot air guns suitable for this application are commercially available from Leister Elektro-Geratebau of Lucerne, Switzerland. 
     After sleeve  120  is disposed about tubular members  50 ,  51 , heat and pressure are applied to joining regions  52 ,  53  to form a bond. Having formed a bond, the assembly is then allowed to cool. The assembly may be submersed in a relatively cool fluid to speed cooling of the assembly. Examples of fluids which may be suitable for some applications include water and air. Relatively cool air may also be impinged onto the assembly. Cold air generators suitable for this purpose are commercially available from ITW Vortec of Cincinnati, Ohio and Exair Corporation of Cincinnati, Ohio. After the assembly has cooled, sleeve  120  is removed. This may be accomplished by scoring sleeve  120  with a cutting tool, and peeling it away from the catheter assembly. 
     The mandrel  100  is then removed from the lumen of the catheter assembly. In a preferred method, the outer surface of mandrel  100  includes polytetrafluoroethylene (PTFE). PTFE is preferred because it provides a substantially non-stick surface. This substantially non-stick surface aids in the removal of mandrel  100  from the lumen of the catheter assembly. 
     FIG. 7 is a plan view of the proximal portion  16  of a catheter  10  in accordance with the present invention. Catheter  10  of FIG. 7, includes a tubular member  50  having a bonding region  52 . Catheter  10  also includes a strain relief  32  disposed about a portion of proximal portion  16  of catheter  10 . Catheter  10  also includes a hub  30  having a bonding region  200 , a coupling region  202 , and a strain relief region  32 . As shown in FIG. 7, bonding region  200  of hub  30  is generally disposed about and bonded to bonding region  52  of tubular member  50 . 
     Bonding region  52  of tubular member  50  includes a plurality of ribs  60 . Bonding region  200  of hub  30  includes a plurality of grooves  204  corresponding to ribs  60  of tubular member  50 . As shown in FIG. 7, ribs  60  of tubular member  50  are generally disposed in grooves  204  of hub  30 . The interlocking geometry of ribs  60  and grooves  204  increases the mechanical strength of the resulting joint. Coupling region  202  of hub  30  is adapted to form a mating connection with other devices. Specifically, coupling region  202  is adapted to form a connection which places another device in fluid communication with a lumen  206  of hub  30 . In one embodiment of the present invention, coupling region  202  includes a leur fitting. 
     A method of creating a hub bonded to a tubular member in accordance with the present invention may be described making reference to FIG. 7. A preferred method, begins with the step of forming ribs  60  in joining region  52  of tubular member  50 . A variety of manufacturing methods may be used to form ribs  60  on tubular section  60  including material forming processes and material removal processes. Examples of material removal processes which may be acceptable in some applications include turning on a lathe and centerless grinding. An example of a material forming process which may be acceptable in some applications is forging ribs by compressing joining region  52  of tubular member  50  in a heated tool of the desired shape. 
     The proximal portion of tubular member  50  including joining region  52  is then positioned inside a mold cavity and molten plastic is injected into the mold. The molten plastic surrounds joining region  52  of tubular member  50  forming grooves  204  corresponding to ribs  60 . The molten plastic is then allowed to cool and solidify forming hub  30 . Once hub  30  has been formed, it is removed from the tool. The interlocking geometry of ribs  60  and grooves  204  increases the mechanical strength of the resulting joint. 
     Having thus described the preferred embodiments of the present invention, those of skill in the art will readily appreciate that yet other embodiments may be made and used within the scope of the claims hereto attached. 
     Numerous advantages of the invention covered by this document have been set forth in the foregoing description. It will be understood, however, that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of parts without exceeding the scope of the invention. The invention&#39;s scope is, of course, defined in the language in which the appended claims are expressed.