Radiopaque super-elastic intravascular stent

Abstract

The intravascular stent is formed from a composite wire includes an inner core of radiopaque metal, a polymer layer coaxially disposed about the inner core, and an outer metal layer coaxially disposed about the polymer layer. The intermediary polymer layer acts as a barrier material between the inner core and the outer sheath, so that the inner core and outer sheath may be made of dissimilar metallic layers, and the intermediary polymer layer will prevent a galvanic reaction between the inner core and the peripheral metal layer. The intravascular stent has ends flared radially outwardly to prevent radially and longitudinally inward deformation of the ends of the stent when the stent is disposed in a desired location in a patient's vasculature.

1 . A cylindrical mandrel, comprising:
 a cylindrical main body having first and second opposing ends and a longitudinal axis;   a first set of four orthogonally arranged pegs extending from the cylindrical main body at the first end of the cylindrical main body;   a second set of four orthogonally arranged pegs extending from the cylindrical main body at the second end of the cylindrical main body;   a first conical end cap mounted to said first end of said cylindrical main body; and   a second conical end cap mounted to the second end of the cylindrical main body.   
     
     
         2 . The mandrel of  claim 1 , wherein said first and second conical end caps have conically tapered surfaces forming a tapered angle at the first and second ends of the cylindrical main body. 
     
     
         3 . The mandrel of  claim 2 , wherein said tapered angle is about 30° with respect to the longitudinal axis of the cylindrical main body. 
     
     
         4 . A method for forming an intravascular stent, comprising:
 a) providing a cylindrical mandrel including a cylindrical main body having first and second opposing ends and a longitudinal axis, a first set of four orthogonally arranged pegs extending from the cylindrical main body at the first end of the cylindrical main body, a second set of four orthogonally arranged pegs extending from the cylindrical main body at the second end of the cylindrical main body, a first conical end cap mounted to said first end of said cylindrical main body, and a second conical end cap mounted to the second end of the cylindrical main body;   b) winding a single composite wire about a first peg of the first set of pegs at the first end of the cylindrical mandrel to form a first end loop portion at a first end of a stent, and thereafter transitioning to form an intermediate circumferential loop;   c) winding the composite wire about a first peg of the second set of pegs at the second end of the cylindrical mandrel to form a first end loop portion at a second end of the stent, and thereafter transitioning to form an intermediate circumferential loop; and   d) repeating steps b) and c) alternatingly, beginning with one of steps b) and c), to continue sequentially to form a plurality of intermediate circumferential loops between a plurality of end loop portions at the first and second ends of the cylindrical mandrel.   
     
     
         5 . The method of  claim 4 , wherein said plurality of intermediate circumferential loops between said plurality of end loop portions form an intermediate tubular body portion, said intermediate tubular body portion having a first diameter, an enlarged first end and an enlarged opposing second end, and said enlarged first and second ends having a second diameter greater than the first diameter of the intermediate tubular body portion. 
     
     
         6 . The method of  claim 4 , wherein said single composite wire comprises a spirally wound composite wire including an elongated inner core having a selected length and an outer metal layer coaxially disposed around said elongated inner core along the length of said elongated inner core. 
     
     
         7 . The method of  claim 6 , wherein said elongated inner core and said outer metal layer are made of dissimilar metals, and a continuous intermediate polymer layer is disposed between said outer metal layer and said elongated inner core, said continuous intermediate polymer layer being configured to prevent current flow between said elongated inner core and said outer metal layer. 
     
     
         8 . The method of  claim 4 , wherein said intravascular stent takes on a linear shape when stretched, without the ends shrinking to a diameter less than the diameter of the central body of the stent when disposed in a desired location in a patient's vasculature. 
     
     
         9 . The method of  claim 5 , wherein a plurality of said end loop portions flare radially outward with respect to the intermediate tubular body portion of the stent. 
     
     
         10 . The method of  claim 7 , wherein said continuous intermediate polymer layer is formed from a polymer selected from the group consisting of polytetrafluoroethylene, poly-para-xylylene, a fluorine substituted poly-para-xylylene, and combinations thereof. 
     
     
         11 . The method of  claim 7 , wherein said outer metal layer is formed of a superelastic alloy. 
     
     
         12 . The method of  claim 7 , wherein said outer metal layer is formed of nitinol. 
     
     
         13 . The method of  claim 7 , wherein said composite wire is formed as a cylindrical wire.