Abstract:
This invention is directed at an intravascular balloon catheter. The most important aspect of this invention is the catheter tip which is small, soft and truncated. The tip member has a proximal end and a distal end. The proximal end is secured to the distal end of the inner tubular member of the catheter shaft. The distal end has proximal and distal leading edges which reduce the overall profile of the catheter. Moreover, the catheter tip is formed from pliant materials so that trauma to the blood vessel walls can be minimized.

Description:
BACKGROUND 
     This invention generally relates to intravascular catheters used for stent delivery and percutaneous transluminal coronary angioplasty (PTCA). 
     PTCA is a widely used procedure for the treatment of coronary heart disease. In this procedure, a balloon on the catheter is inflated within the stenotic region of the patient&#39;s artery to open up the arterial passageway and thereby increase the blood flow through the artery. 
     Typically, a guiding catheter having a preshaped distal tip is first percutaneously introduced into the cardiovascular system of a patient by the Seldinger technique through the brachial or femoral arteries. The catheter is advanced until the preshaped distal tip of the guiding catheter is disposed within the aorta adjacent to the ostium of the desired coronary artery; and the distal tip of the guiding catheter is then maneuvered into the ostium. A balloon dilation catheter may then be advanced through the guiding catheter into the patient&#39;s coronary artery until the balloon on the catheter is disposed within the stenotic region of the patient&#39;s artery. The balloon is inflated to open up the arterial passageway. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilation but not over expand the artery wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilation catheter can be removed. 
     A continual effort has been made in the development of intravascular catheters, to reduce the transverse dimensions or profiles of such catheters, particularly at the catheter tip. A catheter having a small or reduced profile generally has a greater ability to cross lesions and tight vasculatures. Despite much technical progress in this area, the need for intravascular catheters having greater reduced profiles at the catheter tip remains. The present invention satisfies these needs. 
     SUMMARY 
     The present invention is an intravascular balloon catheter having a small profile distal tip. In one embodiment, the distal tip generally includes a forward face with a proximal edge and a distal edge on opposite sides of the catheter shaft and a face which tapers in a distal direction from the proximal edge to the distal edge. Because the tip member is tapered from the proximal edge to the distal edge, the shape of the distal tip is similar to that of a truncated cylinder which provides the distal edge of the tip member with a low profile. The small profile and chisel-like shape of the truncated distal tip improves the overall ability of this catheter to cross any stenosis. Once the distal edge is eased through a stenosed region, sections of the catheter proximal thereto can be readily advanced across the stenosis. The truncated distal tip defines an elliptical port in the distal end thereof. The elliptical port facilitates backloading of a guidewire into the guidewire lumen of the catheter shaft, in which the proximal end of the guidewire is introduced into the distal port of the catheter, by providing a larger opening than the cylindrical port of a prior art distal tip. 
     The distal tip may be formed as a single unit with the catheter shaft, or alternatively, as a separate member which is secured to a distal end of the catheter shaft. The distal tip is preferably formed of a soft material, to thus avoid causing trauma and tissue damage as it is advanced through the blood vessels. 
     In another embodiment, the truncated distal tip further includes a first side and a second side on opposite sides of the catheter shaft longitudinal axis, the first side and the second side each tapering distally toward a center of the catheter shaft from a larger outer diameter to a smaller outer diameter, to thus form a wedge-like structure. 
     Another embodiment of the invention generally comprises a distal tip with a proximal end, and a distal end having an outer diameter along a first plane which is not less than an outer diameter of the proximal end of the distal tip, and with a first side and a second side on opposite sides of the catheter shaft longitudinal axis, the first side and the second side each tapering distally along a second plane toward a center of the catheter shaft from a larger outer diameter to a smaller outer diameter, to thus form a structure typical of some flat head screwdrivers but with a lumen therein. 
     Unlike the blunt cylindrical tip members of the catheters currently available, the profile of the catheter of the invention is much lower and this improves the ability of the catheter to cross narrowed stenosed regions and to be advanced within narrow vessels. These and other advantages will become more apparent from the following detailed description and accompanying exemplary drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view, partially in section, of a balloon catheter with guidewire in the inner lumen of the catheter. 
     FIG. 2 is a transverse cross-sectional view of the catheter assembly shown in FIG. 1 taken along the line  2 — 2 . 
     FIG. 3 is a transverse cross-sectional view of the catheter assembly shown in FIG. 1 taken along the lines  3 — 3 . 
     FIG. 4 is an enlarged longitudinal, partial in section, view of the catheter shown in FIG. 1 taken in circle  4 , illustrating a prior art catheter distal tip. 
     FIG. 5 is a perspective view of the catheter distal tip shown in FIG. 1 with the guidewire shown in phantom. 
     FIG. 6 is an enlarged longitudinal, partial in section, view of a catheter distal tip which embodies features of this invention, having a truncated tip member. 
     FIG. 7 is a perspective view of the catheter tip illustrated in FIG. 6 with the guidewire shown in phantom. 
     FIG. 8 is an enlarged longitudinal, partial in section, view of a truncated distal tip embodying features of the invention, having first and second tapered sides. 
     FIG. 9 is a perspective view of the tip shown in FIG. 8 with the guidewire shown in phantom. 
     FIG. 10 is an enlarged longitudinal, partial in section, view of a catheter tip which embodies features of the invention, having first and second tapered sides forming a flat head screwdriver shaped distal tip. 
     FIG. 11 is a perspective view of the distal tip shown in FIG. 10 with the guidewire shown in phantom. 
     FIG. 12 is a plan view of the distal tip shown in FIG.  10 . 
     FIG. 13 is an enlarged longitudinal, partial in section, view of a catheter tip member which embodies features of the invention, with a separate tip member secured to the catheter shaft. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a prior art intravascular balloon catheter  10  having an elongated catheter shaft  11  having a proximal section  12 , a distal section  13 , an adapter  14  secured to a proximal end of the shaft, and an inflatable balloon  15  on the distal shaft section. In the embodiment illustrated in FIG. 1, the catheter shaft comprises an inner tubular member  16  defining a guidewire lumen  17 , within an outer tubular member  18  that is disposed about the inner tubular member and defines therewith inflation lumen  19 . FIG. 2 illustrates the transverse cross sectional view of the catheter taken along line  2 — 2 , and FIG. 3 illustrates the transverse cross sectional view of the catheter taken along line  3 — 3 . Guidewire  20  is disposed within guidewire lumen  17 . 
     In the embodiment illustrated in FIG. 1, the catheter has a conventional, prior art tapered distal tip  22 , as best illustrated in FIG. 4 showing an enlarged view of the distal tip of FIG. 1, taken within circle  4 . FIG. 5 illustrates a perspective view of the distal tip shown in FIG.  4 . The prior art tapered distal tip  22  shown in FIGS. 4 and 5 is cylindrical in shape, with a blunt, flat tip  23  and tapered sides  24 . 
     FIGS. 6 and 7 illustrates an embodiment of the distal tip of the invention, generally comprising a truncated distal tip  30 . It should be understood that the distal tip shown in FIGS. 6 and 7, and the additional embodiments discussed below, could be used on catheter  10  shown in FIG. 1 in place of the conventional distal tip  22  illustrated in FIG. 1, so that the distal tip  30  is on the distal end of inner tubular member  16 . FIG. 6 is a longitudinal, partial in section view of the truncated and tapered catheter tip  30 , and FIG. 7 is a perspective view of the truncated catheter tip  30 . Distal tip  30  has a proximal edge  31 , a distal edge  32  on an opposite side of the catheter shaft, and a face  33  which tapers in a distal direction from the proximal edge  31  to the distal edge  32 . As illustrated in FIGS. 6 and 7, the proximal edge  31  and distal edge  32  of the distal tip  30  are substantially longitudinally aligned with an outer surface  34  of the inner tubular member. The phrase “substantially longitudinally aligned” should be understood to mean that the inner tubular member has an outer diameter equal to or only slightly different from the outer diameter at the proximal and distal edges  31 / 32  of the distal tip  30 . The outer surface  34  of the inner tubular member  16  is axially aligned with the longitudinal axis of the inner tubular member. Distal tip  30  defines lumen  35  therein, in fluid communication with guidewire lumen  17  of the inner tubular member  16 . Distal tip  30  defines an elliptical port  36  in the distal end thereof. 
     Face  33  of distal tip  30  is shown in FIG. 6 generally tapering at an angle of about 45 degrees. However, face  33  may taper at a variety of suitable angles. An angle of about 30 to about 45 degrees is generally preferred, for ease of manufacturing. In the presently preferred embodiment illustrated in FIGS. 6 and 7, the inner tubular member distal tip  30  has an inner diameter (i.e., the diameter of lumen  35 ) which is equal to or not less than an inner diameter of the inner tubular member  16  (i.e., the diameter of lumen  17 ) at a location proximal to the distal tip  30 . The inner diameter of the distal tip 30 is typically about 0.36 mm to about 0.48 mm preferably about 0.40 mm to about 0.45 mm. In the embodiment illustrated in FIGS. 6 and 7, distal tip  30  has an outer diameter measured from the proximal edge  31  to the distal edge  32  which is not less than an outer diameter of the inner tubular member  16  at a location proximal to the distal tip. The inner tubular member distal tip  30  has an outer diameter measured from the proximal edge  31  to the distal edge  32  which is typically about 0.45 mm to about 1.0, preferably about 0.45 to about 0.5, and a length which is typically about 0.5 mm to about 1.5 mm, preferably about 0.5 mm to about 1.0 mm. 
     FIGS. 8 and 9 illustrate another embodiment of the invention comprising distal tip  40 . Distal tip  40  generally comprises the distal tip  30  shown in FIGS. 6 and 7, further including a first side  41 , a second side  42  on an opposite side of the inner tubular member  16  longitudinal axis, the first side  41  and second side  42  each tapering distally toward a center  43  of the inner tubular member  16  from a larger outer diameter edge  44  to a smaller outer diameter edge  45 . FIG. 9 illustrates a perspective view of distal tip  40  shown in FIG.  8 . 
     FIGS. 10-12 illustrate another embodiment of the invention, comprising distal tip  50  generally having a flat head screwdriver shape. Distal tip  50  has a proximal end  51 , and a distal end  52  having an outer diameter along a first plane Z which is not less than an outer diameter of the proximal end  51  of the distal tip, and with a first side  53  and a second side  54  on opposite sides of the inner tubular member longitudinal axis, the first side  53  and the second side  54  each tapering distally in a second plane X inwardly toward a center of the inner tubular member from a larger outer diameter to a smaller outer diameter. The distal end of the first side  53  of the distal tip adjoins, or may be adjacent to, the distal end of the second side  54  of the distal tip to form the distal end  52  of the distal tip  50 . FIG. 10 is a longitudinal, partially in section, view of the distal tip  50 , FIG. 11 is a perspective view of the distal tip  50  shown in FIG. 10, and FIG. 12 is a plan view of the distal tip  50 . 
     The distal tip of the invention may be formed as a single unit with the inner tubular member  16 , or alternatively, as illustrated in FIG. 13, distal tip may be a separate unit  60  secured to the distal end of the inner tubular member  16 . FIG. 13 is an enlarged longitudinal partial in section view of distal tip  60 , which may be secured to inner tubular member using conventional means such as adhesive or fusion bonding. The figure also illustrates how the inner lumen of the tip member is in fluid communication with the inner lumen of the catheter shaft. The balloon  15  distal shaft section may be secured to either one or both of the inner member  16  and the distal tip  30 / 40 / 50 / 60 . 
     The wall thickness of the distal tip of the invention is typically about 0.03 mm to about 0.04 mm. The small non-cylindrical tip member is typically produced from polymeric materials such as polyamide copolymers such as PEBAX (a polyether block amide), polyurethanes, and polyolefins, and with a Shore Durometer hardness which is preferably about 45 D to about 65 D. Forming the tip member from the above materials makes for a soft tip member that transmits less trauma as the catheter is advanced through the body. 
     While the invention has been discussed in terms of certain preferred embodiments, it should be understood that various modifications may be made without departing from the scope thereof. Moreover, although certain individual features of one embodiment of the invention may be discussed herein or shown in the drawings of the one embodiment and not in other embodiments, it should be apparent that individual features of one embodiment may be combined with one or more features of another embodiment.