Measurements of coronary flow reserve: defining pathophysiology versus making decisions about patient care.

THE POTENTIAL ATTRACTIVENESS of measure- ment of coronary flow reserve in an area ofmyocardium supplied by a stenosed coronary artery has long been recognized.As options for quantifying flow reserve in man have improved, there has been increasing interest in the use of flow reserve measurements to make indi- vidual patient care decisions as well as to define pathophysiology in patient groups.The requirements for effective use in individual patients are in many ways more stringent than in patient groups.Factors that must be considered on an individual rather than group basis include effects of variables potentially affecting flow reserve independently of degree of stenosis, theoretical and practical limitations of specific measurement tech- niques, and confidence limits for procedurally satis- factory measurements. Factors underlying interest in measurements of flow reserve in manLimitations of arteriographic estimates of stenosis severity.Despite the acknowledged pivotal role of coronary arteriography in management decisions in patients with coronary heart disease, the functional significance of an arteriographic lesion often cannot be settled from the arteriogram alone.This point has been emphasized by a number of experimental studies of stenosis behavior, particularly those of Gould.1 It is generally agreed that limitations of arteriographic measurements are most troublesome for stenoses ofmoderate-to-severe degree, i.e., 50% to 90% diameter narrowing.Because