In accordance with one embodiment, a helical anchor is provided in a relaxed state. During deployment, a distal portion of the helical anchor is superelastically deformed to protrude longitudinally. The longitudinally protruding distal portion of the helical anchor is longitudinally advanced to cause the distal portion to pierce a prosthesis and a vessel wall. The distal portion returns to the relaxed state after passing through the prosthesis and the vessel wall. By superelastically deforming the distal portion during deployment, it is easier to cause the anchor to penetrate the prosthesis and the vessel wall. Further, by having the anchor return to its relaxed state after passing through the prosthesis and vessel wall, better clamping of the prosthesis to the vessel wall is achieved.