Multi-property nitinol by heart treatment

Abstract

Medical devices may be made of shape-memory materials portions of which have been heat treated to exhibit spatial variations in the stiffness of the material. Devices including stents, vena cava filters and guidewires may be constructed from such materials. Devices may also be made from shape-memory materials which have been locally heat treated such that the superelasticity of the treated portion is destroyed while the remainder of the shape-memory material can transition between the martensitic and austenitic states.

1 - 23 . (canceled)  
     
     
         24 . A medical guidewire having a proximal end and a distal end, the guidewire having been formed at least in part of a shape-memory metal and wherein different portions of the shape-memory metal have been treated differently to have different shape-memory properties.  
     
     
         25 . The guidewire of  claim 24  wherein different portions of the shape-memory metal are characterized by different stiffnesses.  
     
     
         26 . The guidewire of  claim 24  wherein the shape-memory metal includes a first portion and a second portion, the first and second portions having been annealed in a first annealing step at a first temperature, the second portion having been annealed for an additional period of time at a second temperature in excess of the first temperature.  
     
     
         27 . The guidewire of  claim 24  wherein the distal end of the guidewire has a lower stiffness than the proximal end of the guidewire.  
     
     
         28 . The guidewire of  claim 24  wherein at least a portion of a region extending from the distal end of the guidewire to about 50 cm from the distal end of the guidewire has a lower stiffness than adjacent regions of the guidewire.  
     
     
         29 . The guidewire of  claim 24  wherein a portion of the shape-memory metal has been heat treated to destroy the shape-memory properties of the portion.  
     
     
         30 . The guidewire of  claim 24  wherein the shape-memory metal is a Nickel-Titanium alloy.  
     
     
         31 . The guidewire of  claim 30  wherein the Nickel-Titanium alloy further comprises a dopant selected from the group consisting of Chromium, Niobium, Vanadium and combinations thereof.  
     
     
         32 . A medical device formed at least in part of a shape-memory material wherein at least a first portion of the shape-memory material may transform between a martensitic state and an austenitic state and at least a second portion of the shape-memory material is incapable of transforming to the austenitic state at the same time as the first portion.  
     
     
         33 . The medical device of  claim 32  wherein the second portion has been heat treated to be incapable of transforming to the austenitic state.