a prosthetic heart valve including a supporting structure comprising a substantially semi - circular base or armature of semi - rigid but somewhat flexible material with two upwardly projecting struts . the armature and struts may be encased with plastic or other suitable material ; and are covered with soft flexible material including a strip which connects the free ends of the semi - circular base to form a complete ring . a membrane of biological or biologically acceptable material is shaped about the supporting structure so as to define a cylindrical orifice having lips which overlap , over a significant part of their inside surfaces , to provide a complete and effective closure against and under the force of back - flow . when said lips open the flow is relatively unobstructed . the soft strip of material which completes the armature ring permits the valve to respond more readily to movements of the heart while the semi - rigid section provides adequate support for the valve . the armature and struts may be formed to either a semi - oval or , preferably , semi - circular configuration and made from wire , metal strip , or plastic , or a combination of metal and plastic , all depending upon the application . the struts may be of equal height or different heights . if required the base may be formed completely from metal or plastic .