A prosthetic venous valve having a two-piece housing which includes upstream and downstream sections. The upstream section contains a circular seat against which an occluder comes in sealing contact when the valve is in its closed position. The downstream housing section is shaped so as to prevent escape...http://www.google.com.au/patents/US6315793?utm_source=gb-gplus-sharePatent US6315793 - Prosthetic venous valves
