AUGMENTATION OF LEFT CORONARY INFLOW WITH ELEVATION OF LEFT VENTRICULAR PRESSURE AND OBSERVATIONS ON THE MECHANISM FOR INCREASED CORONARY INFLOW WITH INCREASED CARDIAC LOAD

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Abstract
Left coronary inflow is found to increase significantly in the anesthetized open-chest dog, when the load upon the left ventricle is increased by constriction of the aorta (central to the coronary orifices). This flow response is similar to that obtained previously in the right coronary artery in the presence of pulmonary artery constriction. Measurement of cardiac input and O2 consumption in the presence of an augmented load on either right or left ventricle has demonstrated an increase in the work and metabolism of the respective ventricle. In consideration of the increased coronary inflow observed, the 2 ventricles have at their disposal a compensatory means by which their blood supply can, at least in part, be adjusted to their work and metabolic requirements. It is suggested that the coronary dilatation arises from an increased local production of metabolites and/or the creation of local relative anoxia due to increased O2 utilization. If the expts. are intentionally prolonged (for several hrs.) and the coronary artery is perfused at constant pressure, the coronary flow response ultimately becomes a sustained decrease. As observed under these conditions, and by others using heart-lung and isolated heart preps., the decrease in coronary inflow is regarded as an abnormal response to an increased cardiac load.