Relation Between Myocardial Blood Flow and the Severity of Coronary-Artery Stenosis

Abstract

Comment: At rest (the condition during this study) metabolic demands of the myocardium will be the major determinant of blood flow. Thus the finding that, up to the limits of the coronary artery disease in the patients studied, basal flow was independent of degree of coronary artery stenosis is not surprising. To anesthetists, the study indicates how, in a situation in which myocardial oxygen demand is raised–tachycardia for example, a degree of stenosis that was sufficient for basal oxygen supply needs may be unable to provide flow requirements under the new conditions of oxygen supply and demand, hence the need for careful evaluation of the limited clinical evidence that most of us have of myocardial

function during management of our cases. Clearly, few of us have the sophisticated tools used in this study. Only in some parts of the world is intraoperative echocardiography available. Many of us must rely on the relatively insensitive electrocardiogram or else try to avoid situations in patients with known coronary artery disease that we know increase myocardial oxygen demands. Finally, note that this study had to be limited to patients with single-vessel coronary artery disease only. Where there is multiple vessel disease, the situation is likely to be even more critical. On the other side of the coin is the reassurance that a major degree of vessel stenosis is needed before all coronary vasodilator capacity is lost.