AND BRAUNWALD, E.: Left ventricular performance during muscular exercise in patients with and without cardiac dysfunction. Circulation 34: 597

output and total body oxygen consump-tion (V02) which occur during muscular exercise provide important information con-cerning the overall ability of the cardiovascu-lar system to meet the demands of this com-mon form of stress. It is evident, however, that when a less than normal rise in the cardiac output occurs relative to a given in-crease in V09, it cannot necessarily be con-cluded that the performance of the ventricular myocardium is impaired. Clearly, other factors such as pericardial disease, cardiac arrhyth-mias, or abnormal function of the cardiac valves can markedly impair the cardiac output response to exercise, even when myocardial function is quite normal. Although a number of clinical studies have been reported in which changes in cardiac output and V02 during exercise have been correlated with right heart dynamics,1- ' only a few investigations have made efforts to assess the performance of the left ventricular myocardium during exercise in patients with cardiac disease.6 '0 Moreover, in all but one of the latter studies,10 pulmonary arterial dia-stolic or wedge pressures were utilized as indices of left ventricular end-diastolic pres-sure (LVEDP), and the limitations of these indirect techniques are now generally recog-nized. The mean ejection rate of the left ventricle has also been employed as a measure of left ventricular performance, " and while this index may be useful under certain condi-tions, recent studies indicate that it can be influenced profoundly by changes in heart rate and stroke volume alone.12 It, therefore