a cardiac valve prosthesis having a frame and two or more leaflets attached to the frame . the leaflets are attached to the frame between posts , with a free edge which can seal the leaflets together when the valve is closed under back pressure . the leaflets are created in a mathematically defined shape allowing good wash - out of the whole leaflet orifice , including the area close to the frame posts , thereby relieving the problem of thrombus deposition under clinical implant conditions .