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Abstract

A method and apparatus for selectively engaging and disengaging an anchor to fix a medical device at a selected site within a patient's body. A shape memory alloy (SMA) such as Nitinol is used to fabricate one or more anchors for the medical device. The shape memory effect exhibited by the SMA is thermally activated. One embodiment of the anchor has a substantially circular shape when at its martensite temperature and reverts to an elliptical shape at its austenite temperature. Another embodiment is a substantially straight strip at its martensite temperature and has an end that curls to engage tissue when at its austenite temperature. Still another embodiment includes a pair of anchors that extend outwardly from each side of an elongate probe at their austenite temperature and retract inwardly against the sides of the probe at their martensite temperature. The change in the shape of the SMA elements tends to anchor the medical device or probe at the treatment site. To change the temperature of the SMA elements, an electrical current is selectively energized to provide heat, or thermal conduction between the SMA and a heat source or a heat sink is employed.

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First Claim