Stents for supporting lumens in living tissue

DETAILED DESCRIPTION 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