Extracorporeal circulation system for coronary artery perfusion in the closed-chest dog

An adjustable constant-flow coronary artery perfusion system has been developed for use in the anesthetized closed-chest dog. Coronary flow and perfusion pressure measurements are obtained over the entire autoregulatory range. Coronary flow was briefly diverted to a bypass cannula and then returned to its original level. Coronary vasodilatation resulted in a fall of perfusion pressure below its preocclusion value, but recovery of vascular tone was complete in about twice the time required during unrestricted reactive hyperemia. It is concluded that no flow debt repayment is required for the restoration of vascular tone after brief occlusions. In the measurements made with this system, intramyocardial pressure distribution is not influenced by thoracotomy, pericardotomy, or positive-pressure respiration, and surgical trauma is minimal.