Abstract:
The present invention relates generally to catheters for performing medical procedures including percutaneous transluminal coronary angioplasty. Moreover, the present invention relates to catheters with improved shaft designs, particularly improved flexibility, pushability, torquability, and limited kinking. A catheter shaft, comprising an elongate support member, a longitudinal axis, a sheath disposed about the elongate support member, and at least one gap along the longitudinal axis is disclosed. The gap defines a first edge and a second edge. The gap may comprise a variable taper. Alternately, a first projection extends from the first edge and a second projection extends from the second edge. The projections may comprise interlocking rounded projections, non-interlocking projections, interlocking projections, modified projections of differing shapes, and combinations thereof.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to catheters for performing medical procedures including percutaneous transluminal coronary angioplasty. More particularly, the present invention relates to catheters with improved shaft designs. 
     BACKGROUND OF THE INVENTION 
     The use of intravascular catheters has become an effective method for treating many types of vascular disease. In general, an intravascular catheter is inserted into the vascular system of the patient and navigated through the vasculature to a desired target site. Using this method, virtually any target site in the patient&#39;s vascular system may be accessed, including the coronary, cerebral, and peripheral vasculature. Examples of therapeutic purposes for intravascular catheters include percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA). 
     Intravascular catheters are commonly used in conjunction with a guidewire. A guidewire may be advanced through the patient&#39;s vasculature until it has reached a target location. Once in place, a catheter may be threaded onto the guidewire and urged distally until the distal end of the catheter reaches a target location. 
     Intravascular catheters adapted for use with a guidewire typically are classified as over-the-wire (OTW) or single operator exchange (SOE). An OTW catheter includes a guidewire lumen extending from the distal tip of the catheter to the proximal end of the catheter. When intravascular catheters are used, it is common for physicians to remove one catheter and exchange it for another. While exchanging catheters, the guidewire must be held in place so as to keep its distal end near the target area. A portion of the guidewire is typically grasped by the physician in order to withdraw the first catheter while maintaining the distal end of the guidewire in the desired position. To properly anchor the guidewire, a portion of the guidewire must be exposed at all times so it is available for the physician to grasp. In the case of an OTW catheter, this requires that the length of the guidewire extending beyond the patient&#39;s body be longer than the catheter. Consequently, in many cases intravascular catheters are longer than 200 cm or require guidewire extensions to facilitate exchange. Correspondingly, there may be more than 200 cm of wire extending from the patient. Managing this length of wire during a catheter exchange procedure is awkward, and typically requires more than one person. Additionally, contamination must be avoided by assuring that the guidewire is not dropped from the sterile field. 
     SOE catheters were developed in response to difficulties encountered when exchanging OTW catheters. Accordingly, SOE catheters have a relatively short guidewire lumen relative to the length of the catheter. Therefore, the length of guidewire extending beyond the body of the patient need only be slightly longer than the guidewire lumen of the catheter. The physician may anchor or hold the guidewire as the first catheter is removed from the body with the exchange occurring over the shorter guidewire lumen. The guidewire lumen of an SOE catheter typically includes a distal guidewire port disposed at the distal tip of the catheter and a proximal guidewire port disposed proximally of the distal end of the catheter. 
     When in use, intravascular catheters enter a patient&#39;s vasculature at a convenient location and then are urged to a target region. Once the distal portion of the catheter has entered the patient&#39;s vascular system the physician may urge the distal tip forward by applying longitudinal forces to the proximal portion of the catheter. For the catheter to effectively communicate these longitudinal forces it is desirable that the catheter have a high level of pushability and kink resistance particularly near the proximal end. 
     Frequently the path taken by a catheter through the vascular system is tortuous, requiring the catheter to change direction frequently. In some cases, it may even be necessary for the catheter to double back on itself. In order for the catheter to conform to a patient&#39;s tortuous vascular system, it is desirable that intravascular catheters be very flexible, particularly near the distal end. 
     Further, while advancing the catheter through the tortuous path of the patients vasculature, physicians often apply torsional forces to the proximal portion of the catheter to aid in steering the catheter. Torsional forces applied on the proximal end must translate to the distal end to aid in steering. It is therefore desirable that the proximal portion of an intravascular catheter have a relatively high level of torquability to facilitate steering. 
     The need for this combination of performance features is often addressed by manufacturing a catheter that has two or more discrete tubular members having different performance characteristics. For example, a relatively flexible distal section may be connected to a relatively rigid proximal section. When a catheter is formed from two or more discrete tubular members, it is often necessary to form a bond between the distal end of one tubular member and the proximal end of another tubular member. 
     An approach used to enhance pushability and torquability of intravascular catheters is to construct the proximal end from hypodermic tubing, or a “hypotube”. While a hypotube can add significant pushability and torquability to an intravascular catheter due to its intrinsic strength and rigidity, it can kink. 
     A need, therefore, exists for the manufacturing of SOE intravascular catheters to include shaft designs that maintain pushability, flexibility, and torquability while limiting the untoward properties of using a hypotube. 
     SUMMARY OF THE INVENTION 
     The present invention relates generally to catheters for performing medical procedures including percutaneous transluminal coronary angioplasty. More particularly, the present invention relates to catheters with improved shaft designs. Preferably, the catheter shaft comprises an elongate support member with proximal and distal ends, at least one gap within the elongate support member. In a preferred embodiment of the current invention, a sheath is disposed about the elongate support member. 
     In a preferred embodiment of the current invention, the gap defines a first edge and a second edge. Preferably, a first projection extends from the first edge and a second projection extends from the second edge. In an exemplary embodiment, the first projection and the second projection overlap. According to a preferred embodiment, the first edge and the second edge may further comprise additional projections. 
     In an exemplary embodiment of the current invention, a gap within the elongate support member is used to improve its properties. Preferably, the gap improves flexibility while retaining the desired level of pushability and torquability. The gap within the elongate support member may be formed by a number of methods. The methods of forming a gap may include, but are not limited to, cutting (for example laser cutting), sawing, and electrochemical masking. 
     In a particular embodiment of the current invention, a gap defines a first edge and a second edge. Preferably, the gap comprises a variable taper wherein the gap changes from the proximal to distal end. By introducing a taper, the level of flexibility may vary between proximal and distal ends. For example, the taper may result in a gap that is greater near the distal end. This could result in greater flexibility near the distal end of the catheter. 
     In an alternative embodiment of the current invention, the first projection and the second projection are interlocking. In an exemplary embodiment, the first projection is substantially rounded. By interlocking the projections, the elongate support member may retain pushability and torquability while increasing flexibility. Further, altering the shape of the projections can enhance desired flexibility changes throughout the elongate support member. For example, a rounded projection can vary in size along the longitudinal axis of the elongate support member. A specific example may include larger projections near the proximal end and smaller projections near the distal end. In this example, the smaller projections near the distal end may increase flexibility near the distal end of the elongate support member. 
     Additionally, the amount of gap formed between a plurality of projections can vary. For example, the gap between interlocking surfaces may be uniformly altered in differing embodiments. In this example, an elongate support member could be constructed that has increased gap length between interlocking projections at a proximal or distal end that may result in altered flexibility. 
     Further, the gaps formed between interlocking surfaces may vary along the longitudinal axis of the elongate support member. For example, the gap length may be greater near the distal end of the elongate support member. This may result in increased catheter shaft flexibility near the distal end. 
     Additionally, in alternative embodiments of the current invention, the elongate support member may comprise more than one piece. This multi-piece configuration may add beneficial properties to the catheter shaft including, but not limited to, increased flexibility, increased kink resistance, pushability, and torquability. One skilled in the art would be familiar with the advantages of manufacturing a multi-piece configuration that would be appropriate for multiple embodiments of the current invention. Further, the methods for producing a multi-piece elongate support member would be familiar to one skilled in the art. 
     In an alternative embodiment of the current invention, the first projection and the second projection are non-interlocking. The projections could manifest in a multiplicity of shapes according to differing embodiments of the current invention. 
     In an preferred embodiment of the current invention, the gap length for non-interlocking projections can be varied. For example, a projection may have a relatively longer gap in the longitudinal direction (along the longitudinal axis) of the catheter shaft and a relatively shorter gap in the direction perpendicular to the longitudinal axis of the elongate support member. In this example, the catheter shaft may have increased circumferential flexibility while allowing little axial movement. Multiple embodiments of the current invention can be derived that incorporate varied gaps along projections. 
     Additionally, the amount of gap formed between a plurality of projections can vary. For example, the gap between non-interlocking projections may be uniformly altered in differing embodiments. In this example, an elongate support member could be constructed that has increased gap length between non-interlocking projection near a proximal end or a distal end that may result in altered flexibility. 
     In an alternative embodiment of the current invention, the first projection and the second projection may comprise differing shapes. In multiple embodiments of the current invention, the projections could also have varying size and gap length as illustrated above. Further, multiple embodiments can be derived that incorporate varied gaps between projections as illustrated above. Similar alterations can be derived for modified projections of differing shapes. 
     In an alternative embodiment of the current invention, the first edge and the second edge defines a tapered and a non-tapered region. The taper forms a gap that changes from the proximal to the distal end. By introducing both a taper and a non-tapered region, the level of flexibility can vary between proximal and distal ends. For example, a non-tapered region may result in a less flexible region near the proximal end of the catheter and the taper may result in a gap that is greater near the distal end. This could result in greater flexibility near the distal end of the catheter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal view of a catheter shaft with an elongate support member comprising a gap defining a first edge and a second edge, wherein the gap comprises a taper; 
     FIG. 2 is a cross-sectional view of the catheter shaft that depicts the wider gap of the taper; 
     FIG. 3 is a cross-sectional view of the catheter shaft that depicts the narrower gap of the taper; 
     FIG. 4 is a longitudinal view of a catheter shaft with an elongate support member comprising a first projection and a second projection wherein the projections are rounded and interlocking; 
     FIG. 5 is a cross-sectional view of the catheter shaft that depicts the gap near the interlocking projections; 
     FIG. 6 is an alternate cross-sectional view of the catheter shaft that depicts a minimum gap near the interlocking projections; 
     FIG. 7 is an alternate cross-sectional view of the catheter shaft that depicts a gross gap near the interlocking projections; 
     FIG. 8 is a longitudinal view of a catheter shaft with an elongate support member comprising a first projection and a second projection wherein the projections are non-interlocking; 
     FIG. 9 is a longitudinal view of a catheter shaft with an elongate support member comprising a first projection and a second projection wherein the projections are interlocking; 
     FIG. 10 is an enlarged longitudinal view the first projection; 
     FIG. 11 is a longitudinal view of a catheter shaft with an elongate support member comprising a first projection and a second projection wherein the projections are of differing shapes; and 
     FIG. 12 is a longitudinal view of a catheter shaft with an elongate support member comprising a first edge and a second edge, wherein the gap defines both a tapered and a non-tapered region. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings wherein like reference numerals indicate like elements throughout the several views, FIG. 1 is a longitudinal view of a catheter shaft with an elongate support member comprising a gap that defines a first edge and a second edge, wherein the a gap comprises a taper. Catheter shaft  10  comprises elongate support member  12  disposed within a sheath (not shown in FIG. 1, see FIG.  2 ). Elongate support member  12  can be manufactured from multiple materials including, but not limited to, thermoplastics, high performance engineering resins, polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polyurethane, polytetrafluoroethylene (PTFE), polyether-ether ketone (PEEK), polyimide, polyamide, polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polysufone, nylon, perfluoro(propyl vinyl ether) (PFA), metal, stainless steel, metal alloys, nickel alloys, and nickel titanium alloys. Additionally, elongate support member  12  can be formed from hollow cylindrical stock or a flat sheet that is cut and rolled. 
     A sheath disposed about elongate support member  12  can be manufactured from materials including, but not limited to, thermoplastics, high performance engineering resins, polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polyurethane, polytetrafluoroethylene (PTFE), polyether-ether ketone (PEEK), polyimide, polyamide, polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polysufone, nylon, or perfluoro(propyl vinyl ether) (PFA). One skilled in the art would be able to determine which material to use for manufacturing a sheath for a catheter according to multiple embodiments of the current invention. 
     A gap within elongate support member  12  defines a first edge  13  and a second edge  15 , and comprises a taper  16  between the proximal and distal ends. Preferably taper  16  varies between proximal and distal ends. Taper  16  comprises a narrower gap  18  and a wider gap  20 . By introducing taper  16 , the level of flexibility may vary between proximal and distal ends. For example, taper  16  may result in a gap that is greater near the distal end of the catheter shaft. This could result in greater flexibility near the distal end of the catheter. Cross-sections cut through elongate support member  12  include line  2 — 2  (shown in FIG. 2) and line  3 — 3  (shown in FIG.  3 ). 
     In multiple embodiments of the current invention, at least one gap is formed within the elongate support member to improve its properties. Preferably, the gap improves flexibility while retaining the desired level of pushability and torquability. The shaft may be cut by a number of methods, which are known to one skilled in the art. The methods of cutting may include, but are not limited to, laser cutting, sawing, and electrochemical masking. 
     FIG. 2 is a cross-sectional view of catheter shaft  10  from FIG. 1 that depicts the wider gap of variable taper  16 . The wider gap can provide increased flexibility of the catheter. Preferably, the wider gap is near the distal end of the catheter. The cross-section of catheter  10  includes elongate support member  12  disposed within sheath  14 . 
     FIG. 3 is a cross-sectional view of catheter shaft  10  from FIG. 1 that depicts the narrower gap of variable taper  16 . The narrower gap may provide less flexibility of the catheter. Preferably, the narrower gap is near the proximal end of the catheter. The cross-section of catheter shaft  10  includes elongate support member  12  disposed within sheath  14 . 
     FIG. 4 is a longitudinal view of a catheter shaft  110 , comprising an elongate support member  112  disposed within a sheath (not shown in FIG. 4, see FIG.  5 ), a gap  28  defining first edge  113  and second edge  115 , a first projection  26  extending from first edge  113 , and a second projection  27  extending from second edge  115 . Preferably, first projection  26  and second projection  27  are interlocking. By interlocking projections, shaft  110  may retain pushability and torquability while increasing flexibility. A cross-sectional through the elongate support member  12 , line  4 — 4 , includes at least one gap  28 . Preferably, first projection  26  and second projection  27  overlap. 
     Altering the shape of gap  28  can enhance desired flexibility changes throughout the catheter. In an exemplary embodiment, first projection  26  and second projection  27  are substantially rounded. For example, rounded projections can vary in size along the longitudinal axis of the elongate support member. A specific example may include larger rounded projections near the proximal end and smaller projections near the distal end. In this example, the smaller projections near the distal end may increase flexibility near the distal end of the catheter shaft. 
     Additionally, rounded projections can vary in the amount of gap  28  formed between a plurality of interlocking projections. For example, gap  28  between interlocking projections may be uniformly altered in differing embodiments. In this example, catheter shaft  110  could be constructed that has increased gap length between interlocking projections that may result in increased flexibility. 
     Further, the gaps formed between interlocking projections may vary along the longitudinal axis of the elongate support member. For example, the gap length may be greater near the distal end. This may result in increased catheter shaft flexibility near the distal end of the elongate support member. The ability to alter gap lengths at different points along the longitudinal axis creates countless possible configurations that may each have a beneficial configuration for differing embodiments of the current invention. 
     FIG. 5 is a cross-sectional view of catheter shaft  110  from FIG. 4 that depicts gap  28 . Catheter shaft  110  according to this embodiment of the current invention comprises elongate support member  112  disposed within sheath  114 . 
     FIG. 6 is an alternative cross-sectional view of catheter shaft  110  from FIG. 4 that depicts a minimum gap  128  that approaches zero. A catheter shaft  210  according to this embodiment of the current invention comprises an elongate support member  212  disposed within a sheath  214 . By minimizing the gaps it may be possible to control flexibility for multiple embodiments of the current invention. 
     Additionally, by forming a plurality of gaps, the elongate support member may be divided into more than one piece. This multi-piece configuration may add beneficial properties to the catheter shaft including, but not limited to, increased flexibility, increased kink resistance, pushability, and torquability. 
     FIG. 7 is an alternative cross-sectional view of catheter shaft  110  from FIG. 4 that depicts a gross gap  228 . A catheter shaft  310  according to this embodiment of the current invention comprises an elongate support member  312  disposed within a sheath  314 . By forming larger gaps it may be possible to control flexibility for multiple embodiments of the current invention. 
     FIG. 8 is a longitudinal view of a catheter shaft  410 , comprising an elongate support member  412  disposed within a sheath (not shown), a gap  328  that defines first edge  213  and second edge  215 , first projection  126  extending from first edge  213 , and second projection  127  extending from second edge  215 . The projections could manifest in a multiplicity of shapes according to differing embodiments of the current invention. In multiple embodiments of the current invention, the projections could also have varying size and gap length. Preferably, first projection  126  and second projection  127  overlap. 
     Altering the shape of the projections can enhance desired flexibility changes throughout the shaft. For example, the projections can vary in size along the longitudinal axis of the elongate support member. A specific example may include larger projections near the proximal end and smaller projections near the distal end. In this example, the smaller projections near the distal end may increase flexibility near the distal end of the catheter. 
     The projections may also vary in the amount of gap  328  formed between a plurality of surfaces of the elongate support member. For example, gap  328  between surfaces of the elongate support member may be uniformly altered in differing embodiments. In this example, catheter shaft  410  could be constructed that has increased gap length between surfaces that may result in increased flexibility. 
     Additionally, the gaps formed between surfaces may vary along the longitudinal axis of the elongate support member. For example, the gap length may be greater near the distal end of the shaft. This may result in increased catheter shaft flexibility near the distal end. The ability to alter gap lengths at different points along the longitudinal axis creates countless possible configurations that may each have a beneficial configuration for differing embodiments of the current invention. 
     FIG. 9 is a longitudinal view of a catheter shaft  510 , comprising an elongate support member  512  disposed within a sheath (not shown), gap  428  that defines a first edge  313  and second edge  315 , first projection  226  extending from first edge  313 , and second projection  227  extending from second edge  315 . Preferably, first projection  226  and second projection  227  are interlocking. The projections could comprise a multiplicity of shapes according to differing embodiments of the current invention. In multiple embodiments of the current invention, the projections could also have varying size and gap length. Preferably, first projection  226  and second projection  227  overlap. 
     Altering the shape of the projections can enhance desired flexibility changes throughout the catheter shaft. For example, the projections can vary in size along the longitudinal axis of the elongate support member. A specific example may include larger projections near the proximal end and smaller projections near the distal end. In this example, the smaller projections near the distal end may increase flexibility near the shaft&#39;s distal end. 
     Additionally, the projections can vary in the amount of gap  428  formed between a plurality of surfaces of the shaft. For example, gap  428  between surfaces may be uniformly altered in differing embodiments. In this example, shaft  510  could be constructed that has increased gap length between surfaces that may result in increased flexibility. 
     Further, the gaps formed between surfaces may vary along the longitudinal axis of the elongate support member. For example, the gap length may be greater near the distal end. This may result in increased catheter shaft flexibility near the distal end of the catheter shaft. The ability to alter gap lengths at different points along the longitudinal axis creates countless possible configurations that may each have a beneficial configuration for differing embodiments of the current invention. 
     FIG. 10 is an enlarged longitudinal view of first projection  226  that wherein it has differing gap lengths. The gap length can be varied along particular surfaces of a given projection. For example, a projection may have a relatively longer gap  528  in the longitudinal direction (along the longitudinal axis) of the catheter shaft and a relatively shorter gap  628  in the direction perpendicular to the longitudinal axis of the shaft. In this example, the catheter shaft may have increased circumferential flexibility while allowing little axial movement. Multiple embodiments of the current invention can be derived that incorporate varied gaps between surfaces of projections. Similar alterations can be derived for non-interlocking or rounded projections. 
     FIG. 11 is a longitudinal view of a catheter shaft  610 , comprising an elongate support member  612  disposed within a sheath (not shown), a gap  728  defining first edge  413  and second edge  415 , a first projection  326  extending from first edge  413 , and a second projection extending from second edge  415 . In multiple embodiments of the current invention, the projections could also have varying size and gap  728  length as illustrated above. Further, multiple embodiments can be derived that incorporate varied gaps  728  between surfaces of projections. Similar alterations can be derived for non-interlocking modified projections of differing shapes. Preferably, first projection  326  and second projection  327  overlap. 
     The projections can vary in the amount of gap  728  formed between a plurality of surfaces of the elongate support member. For example, gap  728  between surfaces may be uniformly altered in differing embodiments. In this example, shaft  610  could be constructed that has increased gap length between surfaces that may result in increased flexibility. 
     Further, the gaps formed between surfaces may vary along the longitudinal axis of the elongate support member. For example, the gap length may be greater near the distal end. This may result in increased catheter shaft flexibility near the distal end of the catheter shaft. The ability to alter gap lengths at different points along the longitudinal axis creates countless possible configurations that may each have a beneficial configuration for differing embodiments of the current invention. 
     FIG. 12 is a longitudinal view of a catheter shaft  710 , comprising an elongate support member  712  disposed within a sheath (not shown), and a taper  32  that defines first edge  513  and second edge  515 . According to a preferred embodiment, taper  32  comprises a tapered  32  and a non-tapered region  34 . By introducing both tapered  32  and non-tapered region  34 , the level of flexibility can vary between proximal and distal ends. For example, the non-tapered region may result in a less flexible region near the proximal end of the catheter and the taper may result in a gap that is greater near the distal end of the catheter shaft. This could result in greater flexibility near the distal end of the catheter. 
     Elongate support member  712  may further comprise a variable taper as is FIG. 1. A variable taper comprises a narrower gap and a wider gap. By introducing a variable taper, the level of flexibility may vary between proximal and distal points along the elongate support member. For example, the taper may result in a gap that is greater near the distal end of the shaft. This could result in greater flexibility near the distal end of the catheter. 
     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 steps 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.