The anatomy of the sinus of Valsalva.

The anatomy of the aortic root has been studied in different species, and common structural features of importance have been detailed. The findings confirm the universal presence of a wellmarked ridge limiting the distal extent of the aortic sinuses. Redefining the sinuses in this way shows that normally the coronary ostia lie within the sinus proximal to the ridge and it appears that their position relative to the ridge is related to an animal's fleetness. Aortic cusps in the fresh state have no recoil tendency to bring them into apposition but lie in a collapsed open position. It is suggested that prosthetic outflow valves should imitate the normal valve in this important respect.