Effect of aspirin and epinephrine on experimentally induced thrombogenesis in dogs. A parallelism between in vivo and ex vivo thrombosis models.

Thrombosis on the damaged or ruptured vascular wall in a stenotic coronary artery is believed to be the precipitating factor leading to unstable angina. Little is known about the nature of the interactions among platelets, fluid dynamic factors, and vessel wall properties under such conditions. In the present investigation we have compared two experimental models of thrombosis simultaneously in anesthetized dogs. The first was an in vivo model of unstable angina, in which a fixed circumflex coronary artery stenosis was produced and the resultant cyclic blood flow reductions (CFRs) through the vessel were investigated after infusion of aspirin and a combination of aspirin and epinephrine. As previously reported, aspirin inhibited the CFRs, but the continuous infusion of epinephrine reestablished the appearance of CFRs. The second was an ex vivo model, in which thrombus formation on a type III collagen surface was investigated in a parallel-plate perfusion system under controlled conditions of exposure time...