Devices configured from heat shaped, strain hardened nickel-titanium
View Patent ↗Cold worked nickel-titanium alloys that have linear pseudoelastic behavior without a phase transformation or onset of stress-induced martensite as applied to a medical device having a strut formed body deployed from a sheath is disclosed. In one application, an embolic protection device that employs a linear pseudoelastic nitinol self-expanding strut assembly with a small profile delivery system for use with interventional procedures is disclosed. The expandable strut assembly is covered with a filter element and both are compressed into a restraining sheath for delivery to a deployment site downstream and distal to an interventional procedure. Once at the desired site, the restraining sheath is retracted to deploy the embolic protection device, which captures flowing emboli generated during the interventional procedure. Linear pseudoelastic nitinol is used in the medical device as distinct from non-linear pseudoelastic (i.e., superelastic) nitinol.
1. An embolic protection filter system for use in a body lumen, comprising:
a tubular body with self-expanding struts having a compressed state and an expanded state;
the tubular body including a nickel-titanium alloy, wherein said nickel-titanium alloy:
further comprises platinum;
has a transformation temperature greater than about 37 degrees C.; and
is always in the martensitic phase and exhibits linear pseudoelasticity when deployed with the body lumen;
a shaft extending distally from a distal end of the tubular body; and
a filter element joined to the tubular body, the filter element extending proximally from a shaft distal end, the filter element configured to expand radially outwardly from the shaft and extend about a portion of the shaft when the self-expanding struts of the tubular body are in the expanded state.
2. The embolic filter system of claim 1 , wherein the system includes a sheath at least partially overlying and holding the tubular body in a compressed state and maintaining the tubular body in the martensitic phase.
3. The embolic filter system of claim 1 , wherein a Young's Modulus for the linear pseudoelastic nickel-titanium alloy is less than steel and greater than non-linear pseudoelastic nickel-titanium.
4. The embolic filter system of claim 1 , wherein the shaft comprises a guidewire.