Coronary Blood Flow and Myocardial Oxidative Metabolism at Rest and during Exercise in Subjects with Severe Aortic Valve Disease.

AVAILABLE data concerning coronary flow in intact human subjects have indicated that there is a strong tendency for the blood flow per unit weight of myocardium to fall in the usual range under a wide variety of circumstances and for the coronary vessels to be capable of adapting themselves to most situations sufficiently well to maintain usual coronary flow as long as myocardial metabolism is not deranged.' When myocardial metabolism is deranged, the coronary circulation adapts to these derangements as, for example, in thyrotoxicosis2 and thiamine deficiency.3 The question of adaptation of human coronary flow to mechanical interference prompted the present study of coronary blood flow in subjects with aortic valve disease because of the following considerations. The best current estimates from animal studies indicate that the major portion of coronary flow occurs during diastole, even though flow during systole is considerable.4' It has been emphasized repeatedly, however, that the time of flow into the coronary arteries, as measured by a flowmeter near their aortic origin, may bear little if any relation to flow through the capillary bed and circulatory exchange within the myocardium. Indeed, blood flow out of the coronary sinus is maximal during systole4 and hence during passage through the myocardium the phase of flow shifts 180 degrees. The nitrous oxide meth-