Quantitative evaluation of coronary perfusion in man.

The usefulness and limitations of currently available techniques for quantitating coronary flow in ischemic heart disease are summarized. There are appreciable difficulties in assessing coronary flow solely from an arteriographic evaluation of the epicardial arteries. There is a considerable reserve mechanism for vasodilation at the arteriolar level, and a proximal occlusive lesion produces a reduction in flow only after this distal reserve has been exhausted. In addition, small increments in the severity of established lesions sometimes cause profound reductions in flow. The development of clinically useful flow measurements has been impeded by methodological problems related to nonuniformity of flow within the left ventricle in coronary artery disease. Validation of specific techniques for abnormal situations is difficult but possible and should probably be a prerequisite to the clinical application of any technique. When a methodologically appropriate technique is employed, average left ventricular flow per unit weight is found to be reduced systematically at rest in patients with double- and triple-vessel disease. This reduction is a group difference, however, and is not always evident in individual patients. Accordingly, more recent measurements have concentrated on the assessment of regional perfusion, and two general approaches, selective venous sampling and selective precordial sampling are illustrated. While only preliminary measurements of regional flow are available, it is clear that these measurements offer a more sensitive tool for detecting abnormalities of flow in individual patients and thereby for contributing to the management of specific clinical problems. Measurements of regional flow need to be performed during stress as well as at rest. For the future, there is also need for techniques which can assess transmural variations of flow in man and relate measurements of regional flow to regional oxygen demand. Because of the complexity of current techniques which are methodologically adequate, measurements of coronary flow will, for the immediate future, probably remain confined to clinical centers which have a special interest in them. The effort in these centers will hopefully include significant emphasis on the refinement of existing techniques so that they are more widely applicable.