Described embodiments are directed toward prosthetic valves having leaflets (140) that move asymmetrically in that a leaflet second side region ( 184b ) of the leaflet initially moves toward the open position before a leaflet first side region ( 184a ) and the leaflet first side region initially moves toward the closed position before the leaflet second side region. In the fully open position, the leaflet first side region opens less than the leaflet second side region. Asymmetric opening and final open position, in synchrony with the other leaflets having the same motion and final open position creates spiral flow exiting the open valve that increases blood flow on the downstream side of the leaflet and thus reduces stagnation of the blood that might lead to thrombus formation. Controlled asymmetric movement of the leaflet reduces closing volume by initiating closure on the leaflet first side region and finishing closures on the leaflet second side region.
