Effect of external compression on the postocclusion hyperaemic response of the coronary arteries in the isolated fibrillating dog heart.

The effect of external compression on the postocclusion hyperaemic responses (occlusion time 15, 30, 60 sec) has been studied on the fibrillating canine heart. The heart was placed in a closed organ box containing physiological saline solution, and the coronaries were perfused with blood from a donor dog using a constant volume perfusion technique at 150 mmHg perfusion pressure. The pressure in the organ box varied between 0--50 mmHg. As the compression pressure increased in the organ box, coronary blood flow, basal conductance as well as the parameters of the postocclusion hyperaemic reaction (peak conductance, reactivity, mean transit time of hyperaemia, postocclusive conductance area, and repaymen) decreased. The factors (tissue diffusion, tissue pressure, transmural pressure) at the capillary level can influence the regulation of the postocclusion vasodilatation and the results cannot be explained by metabolic and/or myogenic processes alone.