A blood analogue for the experimental study of flow-related thrombosis at prosthetic heart valves.

It is shown that a flowing mixture of unpasteurised cow's milk, rennet and calcium chloride will deposit solid clot in vitro in the neighbourhood of certain kinds of flow obstruction and hydrodynamic disturbance particularly associated with deposition and thrombus formation in a similar stream of blood. The milk and blood deposits are similar in physical structure, both on a microscopic and a gross scales. For established kinds of artificial heart valves, the growth sequence and developed patterns of milk clotting obtained in vitro with pulsatile flows at physiological rates closely resemble patterns of thrombus reported clinically for valves of the same type in vivo. It appears that these phenomena, for which a tentative explanation is outlined, can form the basis of a convenient and rapid experimental method for evaluating in vitro the effects of design changes on the thrombogenicity of artificial heart valves and other cardiovascular devices in vivo. The milk system also shows promise as an aid in fundamental experimental studies of mechanisms of flow-related thrombosis.