A prosthesis (10, 300) is provided for implantation at a native semilunar valve(140, 310) of a native valve complex. The prosthesis (10, 300) includes a distalfixation member (14), configured to be positioned in a downstream artery (160,314), and shaped so as to define exactly three proximal engagement arms (22) thatare configured to be positioned at least partially within respective ones ofsemilunar sinuses (164), and, in combination, to apply, to tissue that definesthe semilunar sinuses (164), a first axial force directed toward a ventricle.The prosthesis (10, 300) further includes a proximal fixation member (12) coupledto the distal fixation member (14), the proximal fixation member (12) configuredto be positioned at least partially on a ventricular side of the native semilunarvalve (140, 310), and to apply, to the ventricular side of the native valve complex,a second axial force directed toward the downstream artery (160, 314), such thatapplication of the first and second forces couples the prosthesis (10, 300) tothe native valve complex.
