Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Reexamination Certificate
1998-12-24
2001-02-06
Buiz, Michael (Department: 3731)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
Reexamination Certificate
active
06183507
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to stents for supporting lumens in living tissue in order to help hold those lumens open. The lumen may be a blood vessel, a bile duct, or any other similar body conduit that is tending to improperly constrict as a result of disease or malfunction. The lumen may be a graft (whether natural or artificial) in any type of body conduit.
It is known to insert hollow tube-defining structures (“stents”) into tubular body organs or structures such as blood vessels to help open and keep open those body structures. See Boneau U.S. Pat. No. 5,292,331 and Hillstead U.S. Pat. No. 5,135,536 for examples of metal stent structures. (These two references are hereby incorporated by reference herein.) Stents of these types are typically introduced into a blood vessel or other tubular body structure on the deflated balloon of a balloon catheter. When the stent is at the desired location in the tubular body structure, the balloon is inflated to circumferentially expand the stent. The balloon is then deflated and the catheter is withdrawn, leaving the circumferentially expanded stent in the tubular body structure, usually as a permanent prosthesis for helping to hold the tubular body structure open and prevent stenosis or restenosis of that body structure.
While stents and stent applications of the type described above have been found to work extremely well, there may be room for improvement (at least in some cases) in avoiding abrupt transitions between stented and unstented regions of a tubular body structure. Such abrupt transitions may trigger a body reaction at or near the transition. Avoiding abrupt transitions or reducing the abruptness of such transitions may therefore be more therapeutic.
In view of the foregoing, it is an object of this invention to provide improved structures and methods for stenting tubular body structures.
It is a more particular object of this invention to provide stent structures and methods which reduce the abruptness of the transitions between the stented region and the unstented regions in a tubular body structure in which the stent is employed.
SUMMARY OF THE INVENTION
These and other objects of the invention are accomplished in accordance with the principles of the invention by providing stent structures having at least one axial end portion which less strongly holds open or stents the surrounding portion of the tubular body structure in which the stent is being employed than a remaining portion of the stent holds open the portion of the tubular body structure that surrounds the remaining portion. Preferably both axial end portions of the stent are like the above-described end portion, with the above-described remaining portion being medial between the two axial end portions. The axial end portion or portions which less strongly hold open the tubular body structure can be provided in any of a large number of ways. For example, the axial end portion or portions can be made circumferentially weaker (elastically or plastically) than other portions of the stent. (As is explained in more detail below, terms like “plastic” and “plastically” are used herein to mean any type of non-elastic (e.g., permanent) deformation.) Or the axial end portion or portions can be made to recoil somewhat more after circumferential expansion and release than other portions of the stent recoil.
Methods of making stents in accordance with the invention include forming first and second axially spaced, annular stent portions so that the first portion is circumferentially stronger (elastically or plastically) than the second portion. Alternatively, the methods of making stents in accordance with the invention may include forming first and second axially spaced annular stent portions so that the second portion has a higher yield strength than the first portion. The first portion is preferably formed as an axially medial portion of the stent, while the second portion is preferably formed as an axial end portion of the stent. A third annular axial portion of the stent may be formed similarly to the second portion, and is preferably formed as another axial end portion of the stent that is axially remote from the second portion.
Methods of using stents in accordance with the invention include inserting the stent into a tubular body structure, circumferentially expanding the stent, and then releasing the stent so that the tubular body structure can circumferentially recompress a circumferentially weaker, second annular axial portion of the stent more than it recompresses a circumferentially stronger, first annular axial portion of the stent. The weaker portion can be elastically or plastically weaker than the stronger portion. Alternatively, methods of using stents in accordance with the invention include inserting the stent into a tubular body structure, circumferentially expanding the stent, and then releasing the stent so that a second annular axial portion of the stent which has a relatively high yield strength springs back more from circumferential expansion than a first annular axial portion of the stent which has a relatively low yield strength.
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Birdsall Matthew J.
Lashinski Robert D.
Buiz Michael
Medtronic Ave Inc.
Truong Kevin
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