Catheter having an ultra soft tip and methods for making the same

An intravascular balloon catheter having an ultra soft tip. The catheter includes a braided reinforcement member extending substantially the length of the elongate shaft. A balloon is disposed at the distal end of the elongate shaft. An ultra soft tip is formed from a distal portion of balloon material extending distal of the distal end of the elongate shaft.

FIELD OF THE INVENTION

The invention generally relates to intravascular catheters. Specifically, the present invention relates to intravascular balloon catheters including a soft distal tip.

BACKGROUND OF THE INVENTION

Intravascular balloon catheters are used in a wide variety of medical procedures to diagnose and treat vascular abnormalities such as aneurysms, stenotic lesions, intracranial shunts, etc. Such balloon catheters may be used for purposes of dilation, occlusion, flow control, tissue reformation, or the like. Balloons, in particular generally elastic balloons, have also been included on guide catheters to arrest blood flow near a treatment site while another treatment device is extended into a treatment area beyond or distal of the balloon and guide catheter.

Intravascular balloon catheters are commonly navigated through the vasculature to access remote regions of the human body. In order to navigate a vasculature during an intended medical procedure, a catheter must possess opposing characteristics of trackability and flexibility, while retaining a relatively low profile. It is also beneficial that catheters possess a soft distal tip to lessen injury to a vessel wall during navigation through the vasculature.

The hardness or durometer of polymer materials such as those typically used in catheters is commonly measured using the Shore Hardness Test. The Shore Hardness of such materials may be measured by using either the Shore A or Shore D scale. The Shore A scale is used for softer materials, while the Shore D scale is used for harder materials. Both scales range from 0 to 100, where the upper end of the Shore A scale overlaps the lower end of the Shore D scale. For example, a Shore A durometer of 90 is approximately equal to a Shore D durometer of 40. The durometer of the distal tip of exemplary prior art catheters typically are in the range of 35 D to about 70 D. Such distal tips are disclosed in U.S. Pat. No. 6,652,507 issued to Pepin and U.S. Pat. No. 6,368,301 issued to Hamilton et al., the disclosures of each of which are incorporated in their entirety by reference herein.

As catheters are navigated through the vasculature, the distal tip may come into contact with a vessel wall. A hard distal tip formed of the material of the elongate shaft may injure a vessel wall such as a diseased vessel wall. There is a need to provide a catheter with a softer distal tip that can be introduced into a diseased vascular region without causing unnecessary trauma to the vasculature.

SUMMARY OF THE INVENTION

The invention is directed to an intravascular balloon catheter having an ultra soft distal tip. In preferred embodiments, the catheter is a guide catheter including an elastic balloon mounted proximate its distal end. In use, the inflated elastic balloon arrests blood flow near a treatment site while a treatment device extends through the lumen of the guide catheter beyond its distal end to treat the vessel. Accordingly, one embodiment of the invention includes an elongate shaft having a braided reinforcement layer. The reinforcement member can include a metallic or polymeric braided member, single or multiple layers of coiled material or a micromachined tubular member. The micromachined tube can be a hypotube including slots or a spiral cut, for example, to create desired stiffness and flexibility. A polymer layer is disposed about the braided reinforcement layer and may extend distal of the distal end of the braided reinforcement layer. An inflatable balloon is disposed about the distal portion of the elongate shaft and is secured to the polymer layer. A distal portion of the material of the inflatable balloon extends beyond the distal end of the polymer layer to form an ultra soft distal tip. The material of the inflatable balloon and the distal tip is preferably a highly compliant polymer such as a thermoplastic rubber elastomer, providing the catheter with an ultra soft distal tip.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The detailed description and the drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention.

FIG. 1shows an intravascular balloon catheter in accordance with the invention. Catheter10includes a proximal portion20and a distal portion30. The proximal portion20may include a hub assembly40for communicating with the interior of the catheter. The distal portion30may include an expandable balloon50for use during a medical procedure. An elongate shaft60may extend from the proximal portion20to the distal portion30.

FIG. 2shows a distal portion of a catheter in accordance with the invention. Elongate shaft60includes a reinforcement member70which is depicted for the present embodiment as a braided member75. It is, however, recognized that the reinforcement member could include single or multiple layers of coiled or helically wrapped material. Alternatively, a micromachined tubular member could be utilized, for example, a slotted hypotube or a spiral cut hypotube. The reinforcement member70, such as braided member75may extend substantially the length of the elongate shaft60. The braided member75may be formed of materials such as metals, metal alloys, polymers, metal-polymer composites, or other suitable materials. Some examples of some suitable materials may include stainless steels (e.g., 304v stainless steel), nickel-titanium alloys (e.g., nitinol, such as super elastic or linear elastic nitinol), nickel-chromium alloys, nickel-chromium-iron alloys, cobalt alloys, nickel, titanium, platinum, or alternatively, a polymer material such as a high performance polymer, or other suitable materials, and the like.

The braided member75may be covered with a polymer layer80. Polymer layer80may substantially permeate the braided member75, such that braid interstices are substantially filled with the polymer of the polymer layer80. Alternatively or additionally, the polymer layer80may encase the braided member75, such that the polymer layer80forms a discrete layer over the braided member75. The polymer layer80may be formed of a flexible material such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), silicone, fluoropolymer, liquid crystal polymer (LCP), polyimide, polyamide, polyester, polyethylene (PE), polypropylene, polyvinyl chloride (PVC), polyfluorocarbon, polyurethane, polysulfone, ethyl vinyl acetate (EVA), polyether block amide (PEBAX), styrene-ethylene/butylenes-styrene (SEBS), styrene-butadiene-styrene (SBS), polyethylene terephthalate (PET), and their mixtures, alloys, blends, copolymers, and block copolymers. Preferably, polymer layer80may comprise a thermoplastic polyester elastomer having superior flexibility and strength characteristics, such as Hytrel® available from DuPont.

The distal end35of the braided member75may include a segment38free of the polymer layer80. Polymer layer80may be stripped from the segment38during a manufacturing process or polymer layer80may be disposed proximal of segment38prior to securing polymer layer80to the braided member75. The distal segment38may extend a few millimeters. Preferably, segment38may be between about 1.0 and about 2.0 millimeters in length.

A polymer sleeve90may be disposed about segment38of the braided member75. Polymer sleeve90may include a different polymer than that of the polymer layer80. Polymer sleeve90may include a low-density polyethylene (LDPE). Polymer sleeve90preferably provides a strong bonding substrate for the material of the balloon50, whereas the material of the balloon50may not be as readily bondable to the polymer layer80. A proximal portion of the polymer sleeve90may be disposed about and secured to the braided member75. Polymer sleeve90may permeate the interstices of braided member75, or polymer sleeve90may encase the distal segment38of the braided member75forming a discrete layer. A distal portion of the polymer sleeve90may extend distal of the distal end35of the braided member75providing a transition in flexibility of the distal end of the catheter10.

A balloon50is disposed about a distal portion of the elongate shaft60. The balloon50may include a proximal waist portion (not shown), a distal waist portion100, and an intermediate portion105. The balloon50may include a compliant material, such as a thermoplastic rubber elastomer. Preferably, balloon50comprises ChronoPrene™, available from CardioTech International, Inc. ChronoPrene™ is a biocompatible elastomeric material having good surface smoothness and excellent elasticity, and may be processed by conventional melt processing methods. ChronoPrene™ has a durometer hardness of 5-40 Shore A making it an ultra soft material. ChronoPrene™ is readily bondable with low-density polyethylene (LDPE), such as may be used in the polymer sleeve90. The distal waist portion100of the balloon50may be bonded to the polymer sleeve90.

The distal waist portion100extends distal of the polymer sleeve90to form an ultra soft tip120. The ultra soft tip120includes the thermoplastic rubber elastomer of the balloon, thus the ultra soft tip120may have a durometer hardness of 5-40 Shore A. The ultra soft tip120may extend distal of the polymer sleeve90. Preferably, ultra soft tip120extends less than 1.0 millimeters beyond the polymer sleeve90to prevent catheter lumen closure or diameter restriction at the distal tip.

An inner liner65may be disposed within the lumen55of the reinforcement layer70. The inner liner65may extend substantially the length of the catheter shaft or may extend any length thereof. As shown inFIG. 2, the inner liner65may end proximal of the distal end of polymer sleeve90. Preferably inner liner65extends distal of the distal end of braided member75. Such a configuration creates a step-wise transition from the inner liner65, to the polymer sleeve90, to the ultra soft tip120created by the distal extension of the distal balloon waist100. Such a multi-step, step-wise transition creates a region near the distal tip having a multi-step reduction in hardness. Inner liner65may create a lubricious surface having a low frictional coefficient in order to facilitate introduction and advancement of a medical device such as a guidewire or aneurysm treatment catheter (for example, a coil delivery catheter) through the lumen55. Inner liner65may include a polymer material such as fluorinated polyethylene, or the like. Preferably, inner liner65includes a polytetrafluoroethylene, such as Teflon® available from DuPont.

FIG. 3shows an alternate embodiment of a distal tip in accordance with the invention. As shown inFIG. 3, polymer layer80may be a discrete layer disposed about the braided member75. Polymer sleeve90may abut the polymer layer80forming an interface and extend distal of the distal end of braided member75. The distal waist portion100of balloon50extends distal of the polymer sleeve90to form an ultra soft distal tip120.

As shown inFIG. 4, the polymer layer80may extend substantially the entire length of the braided member75. The polymer layer80and the inner liner65may co-terminate at the distal end35of the braided member75. The distal waist portion100of balloon50may be bonded to the polymer layer80at the distal end of elongate shaft60. The distal waist portion100of balloon50may extend distal of the distal end35of the braided member75, forming an ultra soft distal tip120having a durometer of between about 5 A and about 40 A.