Measurements of coronary blood flow and degree of stenosis: current clinical implications and continuing uncertainties.

Initial measurements of coronary blood flow in human beings were limited by methodologic inadequacies causing clinically important areas of reduced perfusion to be incompletely represented or overlooked. More recent measurements have provided insight into clinically relevant pathophysiology. There has been increasing appreciation of the need for values of flow to be related to concomitant myocardial oxygen demand, and of the importance of evaluating perfusion in relation to coronary vascular reserve. Regional flow measurement techniques have progressed significantly during the past decade and have provided better insight into perfusion deficits in ischemic heart disease. A greatly improved understanding of the relation between the arteriographic degree of stenosis and perfusion limitation also has developed. In reviewing studies addressing these points, the present article attempts to highlight their current clinical implications and address continuing uncertainties meriting further attention.