Flow-regulated vs pressure-regulated and pulsatile vs nonpulsatile coronary perfusion in the fibrillating heart were studied in dogs. Conventional total cardiopulmonary bypass was employed and coronary perfusion was achieved via the aortic root. The coronary sinus and right and left ventricles were separately cannulated for drainage and blood sampling for the calculation of oxygen consumption and coronary vascular resistance. It was found that thebesian shunt flow fluctuated widely during coronary perfusion. When shunt flow increased suddenly, flowregulated coronary perfusion could not meet the flow requirements, resulting in inadequate perfusion, in contrast to pressureregulated perfusion.
With pulsatile coronary perfusion it was found that (1) fluctuation of thebesian shunt flow was less, and (2) myocardial oxygen consumption and coronary vascular resistance were more stable than with nonpulsatile coronary perfusion.