Balloon catheter having a small profile catheter

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.

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'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's coronary artery
 until the balloon on the catheter is disposed within the stenotic region
 of the patient'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.

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.