Expandable stents and method for making same

Abstract

The invention is directed to an expandable stent for implantation in a body lumen, such as an artery, and a method for making it from a single length of tubing. The stent consists of a plurality of radially expandable cylindrical elements generally aligned on a common axis and interconnected by one or more interconnective elements. The individual radially expandable cylindrical elements consist of ribbon-like material disposed in an undulating pattern. Portions of the expanded stent project outwardly into engagement with the vessel wall to more securely attach the stent.

What is claimed is:  
     
         1 . A longitudinally flexible stent for implanting in a body lumen, comprising: 
 a plurality of cylindrical elements which are independently expandable in the radial direction and which are interconnected so as to be generally aligned on a common longitudinal axis;    a plurality of connecting elements for interconnecting said cylindrical elements, said connecting elements configured to interconnect only said cylindrical elements that are adjacent to each other; and    an outer wall surface on said cylindrical elements, said outer wall surface having a plurality of outwardly projecting edges which form as said stent is expanded radially outwardly from a first diameter to a second, enlarged diameter.    
     
     
         2 . The stent of  claim 1 , wherein said outer wall surface is substantially smooth when said stent in said first diameter configuration and said outwardly projecting edges form only as said stent is expanded radially outwardly from said first diameter to said second, enlarged diameter.  
     
     
         3 . The stent of  claim 1 , wherein said plurality of outwardly projecting edges extend a distance from said outer wall surface sufficient enough to embed in the vascular wall of the body lumen in order to more firmly attach said stent to the vascular wall.  
     
     
         4 . The stent of  claim 1 , wherein said plurality of cylindrical elements include a plurality of peaks and valleys having a serpentine pattern.  
     
     
         5 . The stent of  claim 4 , wherein said plurality of peaks and valleys include a plurality of U-shaped members, a plurality of Y-shaped members, and a plurality of W-shaped members, some of said U-shaped, Y-shaped, and W-shaped members being interconnected.  
     
     
         6 . The stent of  claim 5 , wherein at least some of said plurality of said U-shaped members tip radially outwardly to form said outwardly projecting edges upon radial expansion of said stent.  
     
     
         7 . The stent of  claim 5 , wherein at least some of said plurality of U-shaped, W-shaped, and Y-shaped members tip radially outwardly to form said outwardly projecting edges upon radial expansion of said stent.  
     
     
         8 . The stent of  claim 1 , wherein said cylindrical elements are capable of retaining their expanded condition upon the expansion thereof.  
     
     
         9 . The stent of  claim 1 , wherein said stent is formed of a biocompatible material selected from the group of materials consisting of stainless steel, tantalum, NiTi alloys, and thermoplastic polymers.  
     
     
         10 . The stent of  claim 1 , wherein said stent is formed from a single piece of tubing.  
     
     
         11 . The stent of  claim 1 , wherein said stent is coated with a biocompatible coating.  
     
     
         12 . A longitudinally flexible stent, comprising: 
 a plurality of cylindrical elements which are independently expandable in the radial direction and which are interconnected so as to be concentrically aligned on a common longitudinal axis; and    a plurality of generally parallel connecting elements for interconnecting said cylindrical elements, said connecting elements configured to interconnect only said cylindrical elements that are adjacent to each other, so that said stent, when expanded radially outwardly, retains its overall length without appreciable shortening.    
     
     
         13 . The stent of  claim 12 , wherein said cylindrical elements are capable of retaining their expanded condition upon the expansion thereof.  
     
     
         14 . The stent of  claim 12 , wherein said radially expandable cylindrical elements in an expanded condition have a length less than the diameter thereof.  
     
     
         15 . The stent of  claim 14 , wherein said stent is formed of a biocompatible material selected from the group consisting of stainless steel, tantalum, super-elastic NiTi alloys, and thermoplastic polymers.  
     
     
         16 . The stent of  claim 12 , wherein said connecting elements between adjacent cylindrical elements are in axial alignment.  
     
     
         17 . The stent of  claim 12 , wherein said connecting elements between adjacent cylindrical elements are circumferentially displaced with respect to said longitudinal axis.  
     
     
         18 . The stent of  claim 17 , wherein the circumferential displacement of said connecting elements between adjacent cylindrical elements is uniform.  
     
     
         19 . The stent of  claim 12 , wherein there are up to four of said connecting elements disposed between adjacent radially expandable cylindrical elements.  
     
     
         20 . The stent of  claim 12 , wherein said radially expandable cylindrical elements and said connecting elements are made of the same material.  
     
     
         21 . The stent of  claim 12 , wherein said stent is formed from a single piece of tubing.  
     
     
         22 . The stent of  claim 12 , wherein the stent is coated with a biocompatible coating.  
     
     
         23 . A kit of parts, comprising: 
 an elongated stent delivery catheter having a proximal end and a distal end, and an expandable member on the distal end; and    a longitudinally flexible stent which is adapted to be slidably mounted onto the expandable member of said catheter and which comprises a plurality of cylindrical elements which are independently expandable in the radial direction and which are interconnected so as to be concentrically aligned on a common longitudinal axis, wherein each said element is formed of a single elongated structural member forming a serpentine pattern having undulations with peaks and valleys, said elements being interconnected by a plurality of generally parallel interconnecting members between adjacent elements, each said interconnecting member configured to interconnect only said cylindrical elements that are adjacent to each other.    
     
     
         24 . A method of transluminally implanting a longitudinally flexible stent in a body lumen, said stent having a plurality of cylindrical elements which are independently expandable in the radial direction and which are interconnected so as to be concentrically aligned on a common longitudinal axis, wherein each said cylindrical element is interconnected a plurality of generally parallel connecting members between adjacent elements, the method comprising the steps of: 
 placing the stent on an expandable portion of a catheter which is adapted to radially expand the stent;  
 delivering the stent to a desired location within the body lumen;  
 expanding said cylindrical elements with the expandable portion of the catheter;  
 contracting the expandable portion of the catheter; and  
 withdrawing the catheter, leaving the expanded stent implanted in the body lumen.