Implantable medical devices of shape memory alloy

A method of deploying a medical device within the human body, the medical device comprising a shape memory alloy (SMA) portion having an austenitic and a martensitic state with a different configuration in each of these states and having associated M.sub.s, M.sub.f, A.sub.s and A.sub.f temperatures, being start and finish temperatures of the SMA's martensitic transformation and the start and finish temperature of the SMA's austenitic transformation, respectively, A.sub.s having the value A.sub.s .degree. which being less than body temperature, when the medical device is in an undeformed state, and M.sub.s being less than A.sub.s, the method comprising the steps of:

• heating the SMA to a temperature greater than A.sub.s, thereby placing the SMA in at least a partial austenitic state;
• cooling the medical device to a temperature between A.sub.s and M.sub.s ;
• deforming the medical device from an undeformed first configuration assumed by it in the austenitic state to a deformed second configuration, said deforming resulting in an increase in A.sub.s from A.sub.s .degree. to A.sub.s ', the SMA portion being in a martensitic or partial martensitic state after said deforming;
• positioning the medical device to a target location within the body, the SMA portion remaining in the martensitic or partial martensitic state during said positioning;
• and
• transforming the SMA portion from the martensitic or partial martensitic state to at least a partial austenitic state by heating it to a temperature higher than A.sub.s ', said transforming resulting in a change in the configuration of the SMA portion from the deformed second configuration towards the undeformed first configuration, the change in configuration resulting in a decrease in A.sub.s from A.sub.s ' to A.sub.s .degree. such that the medical device is stable in at least a partially austenitic state while deployed in the body.

A method of deploying a medical device within the human body, the medical device comprising a shape memory alloy (SMA) portion having an austenitic and a martensitic state with a different configuration in each of these states and having associated M.sub.s, M.sub.f, A.sub.s and A.sub.f temperatures, being start and finish temperatures of the SMA's martensitic transformation and the start and finish temperature of the SMA's austenitic transformation, respectively, A.sub.s having the value A.sub.s .degree., which is less than body temperature, when the medical device is in an undeformed state, the method comprising the steps of:

• deforming the medical device by transforming it from an undeformed first configuration assumed by it in the austenitic state to a deformed second configuration, said deforming resulting in an increase in A.sub.s from A.sub.s .degree. to A.sub.s ', the SMA portion being in a strain-induced martensitic or partial martensitic state after said deforming;
• positioning the medical device to a target location within the body, the SMA portion remaining in the strain-induced martensitic or partial martensitic state during said positioning;
• and
• transforming the SMA portion from said martensitic or partial martensitic state to at least a partial austenitic state by heating it to a temperature higher than A.sub.s ', said transforming resulting in a change in the configuration of the SMA portion from the deformed second configuration towards the undeformed first configuration, the change in configuration resulting in a decrease in A.sub.s from A.sub.s ' to A.sub.s .degree. such that the medical device is stable in at least a partially austenitic state while deployed in the body.