Medical device formed of ultrahigh molecular weight polyolefin

#This invention generally relates to medical devices, and particularly to balloon catheters, stent covers, and vascular grafts.

#In percutaneous transluminal coronary angioplasty (PTCA) procedures, a guiding catheter is advanced until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guidewire, positioned within an inner lumen of an dilatation catheter, is first advanced out of the distal end of the guiding catheter into the patient's coronary artery until the distal end of the guidewire crosses a lesion to be dilated. Then the dilatation catheter having an inflatable balloon on the distal portion thereof is advanced into the patient's coronary anatomy, over the previously introduced guidewire, until the balloon of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the dilatation balloon is inflated with liquid one or more times to a predetermined size at relatively high pressures (e.g. greater than 8 atmospheres) so that the stenosis is compressed against the arterial wall and the wall expanded to open up the 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 dilatation but not overexpand the artery wall. Substantial, uncontrolled expansion of the balloon against the vessel wall can cause trauma to the vessel wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter can be removed therefrom.

#In such angioplasty procedures, there may be restenosis of the artery, i.e. reformation of the arterial blockage, which necessitates either another angioplasty procedure, or some other method of repairing or strengthening the dilated area. To reduce the restenosis rate and to strengthen the dilated area, physicians frequently implant an intravascular prosthesis, generally called a stent, inside the artery at the site of the lesion. Stents may also be used to repair vessels having an intimal flap or dissection or to generally strengthen a weakened section of a vessel. Stents are usually delivered to a desired location within a coronary artery in a contracted condition on a balloon of a catheter which is similar in many respects to a balloon angioplasty catheter, and expanded to a larger diameter by expansion of the balloon. The balloon is deflated to remove the catheter and the stent left in place within the artery at the site of the dilated lesion. Stent covers on an inner or an outer surface of the stent have been used in, for example, the treatment of pseudo-aneurysms and perforated arteries, and to prevent prolapse of plaque. Similarly, vascular grafts comprising cylindrical tubes made from tissue or synthetic materials such as DACRON may be implanted in vessels to strengthen or repair the vessel, or used in an anastomosis procedure to connect vessels segments together.

#FIG. 1 is an elevational view, partially in section, of a balloon catheter for delivering a stent that embodies features of the invention.

#FIG. 2 is a transverse cross-section of the catheter shown in FIG. 1 taken at line 2-2.

#FIG. 3 is a transverse cross-section of the catheter shown in FIG. 1 taken at line 3-3, showing the stent disposed over the inflatable balloon.

#FIGS. 1-3 illustrate an over-the-wire type stent delivery balloon catheter 10 embodying features of the invention. Catheter 10 generally comprises an elongated catheter shaft 12 having an outer tubular member 14 and an inner tubular member 16. Inner tubular member 14 defines a guidewire lumen 18 adapted to slidingly receive a guidewire 20. The coaxial relationship between outer tubular member 14 and inner tubular member 16 defines annular inflation lumen 22. An inflatable balloon 24 disposed on a distal section of catheter shaft 12 having a proximal end sealingly secured to the distal end of outer tubular member 14 and a distal end sealingly secured to the distal end of inner tubular member 16 so that its interior is in fluid communication with inflation lumen 22. An adapter 26 at the proximal end of catheter shaft 12 is configured to direct inflation fluid through arm 28 into inflation lumen 22 and provide access to guidewire lumen 18.

#In the embodiment illustrated in FIG. 1, an expandable stent 30 is mounted on balloon 24. The distal end of catheter may be advanced to a desired region of a patient's body lumen 32 in a conventional manner and balloon 24 may be inflated to expand stent 30, seating it in the lumen.

#In the embodiment illustrated in FIG. 1, the balloon 24 has a layer 34 formed from an elastomeric material, such as polyurethane elastomers, silicone rubbers, styrene-butadiene-styrene block copolymers, and polyamide block copolymers, and the like. In a preferred embodiment, elastomeric layer 34 is on the interior of balloon 24, although in other embodiments it may be on the exterior or the balloon 24. Elastomeric layer 34 expands elastically to facilitate deflation of the balloon 24 to its preinflation diameter and shape, and can also limit or prevent leakage of inflation fluid through the microporous polyethylene.