High strength member for intracorporeal use

Abstract

This invention is directed to an intracorporeal device formed of a high strength Co—Ni—Cr alloy and is particularly suitable for forming a composite product with a pseudoelastic member formed of NiTi alloy. Suitable intracorporeal products include guidewires and stents. The high strength alloy consists essentially of about 28 to about 65% cobalt, about 2 to about 40% nickel, about 5 to about 35% chromium, up to about 12% molybdenum, up to about 20% tungsten, up to about 20% iron and the balance inconsequential amounts of impurities and other alloying constituents, with a preferred alloy composition including about 30 to about 45% cobalt, about 25 to about 37% nickel, about 15 to about 25% chromium and about 5 to about 15% molybdenum. Intravascular devices such as guidewires, stents and the like can be formed of this high strength Co—Ni—Cr alloy.

Description

RELATED APPLICATIONS[0001]This is a continuation application of co-pending application having U.S. Ser. No. 10 / 154,474, filed May 23, 2002; which is a continuation of U.S. Ser. No. 09 / 071,680, filed May 1, 1998; which is divisional of U.S. Ser. No. 08 / 829,465, filed Mar. 28, 1997; which is a continuation of U.S. Ser. No. 08 / 280,209, filed on Jun. 25, 1994; all of whose contents are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]This invention relates to the field of intracorporeal medical devices, and more particularly to elongated intravascular members such as guidewires for percutaneous transluminal coronary angioplasty (PTCA) and stents for maintaining body lumen patency after the body lumen has been dilated with a balloon.[0003]In PTCA procedures a guiding catheter is percutaneously introduced into the cardiovascular system of a patient in a conventional Seldiger technique and advanced therein until the distal tip of the guiding catheter is seated in the ostiu...

AI Technical Summary

Benefits of technology

[0019]The stent of the invention generally includes a plurality of radially expandable cylindrical elements which are relatively independent in their ability to expand and to flex relative to one another. The individual radially expandable cylindrical elements of the stent are dimensioned so as to be longitudinally shorter than their own diameters. Interconnecting elements or struts extending between adjacent cylindrical elements provide increased stability and are preferably positioned to prevent warping of the stent upon the expansion thereof. The resulting stent structure is a series of radially expandable cylindrical elements which are spaced longitudinally close enough so that small dissections in the wall of a body lumen may be pressed back into position against the lumenal wall, but not so close as to compromise the longitudinal flexibility of the stent. The individual cylindrical elements may rotate slightly relative to adjacent cylindrical elements without significant deformation, cumulatively giving a stent which is flexible along its length and about its longitudinal axis but which is still very stiff in the radial direction in order to resist collapse.

[0021]The presently preferred structure for the expandable cylindrical elements which form the stents of the present invention generally have a circumferential undulating pattern, e.g. serpentine. The transverse cross-section of the undulating component of the cylindrical element is relatively small and preferably has an aspect ratio of about two to one to about 0.5 to one (e.g., the ratio of the height to the width of an undulation). A one to one aspect ratio has been found particularly suitable. The open reticulated structure of the stent allows for the perfusion of blood over a large portion of the arterial wall which can improve the healing and repair of a damaged arterial lining.

[0024]The number and location of elements interconnecting adjacent cylindrical elements can be varied in order to develop the desired longitudinal flexibility in the stent structure both in the unexpanded as well as the expanded condition. These properties are important to minimize alteration of the natural physiology of the body lumen into which the stent is implanted and to maintain the compliance of the body lumen which is internally supported by the stent. Generally, the greater the longitudinal flexibility of the stent, the easier and the more safely it can be delivered to the implantation site.

Problems solved by technology

Other methods for determining the stress-strain relationship, e.g., applying a bending moment to a cantilevered specimen, provide a different relationship from the relationship determined by tensile testing, because the stresses which occur in the specimen during bending are not as uniform as they are in tensile testing.

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