US Patent 8021417 Prosthetic valve that permits retrograde flow

A prosthetic valve for regulating fluid flow through a body vessel is provided. The valve includes an expandable support frame and a valve leaflet, and includes at least one opening that permits a controlled amount of retrograde flow through the valve when the valve is in a closed configuration. A flap disposed adjacent the opening is able to temporarily and substantially close the opening to contribute to the regulation of retrograde flow proceeding through the valve.