Comparison of myocardial oxygen consumption indices in man

Abstract

Hemodynamic indices of myocardial oxygen consumption (MV̇O2) were examined in 13 patients with coronary heart disease. The specific aim of this study was to investigate whether clinical results agree with experimental findings in animals. During hemodynamic and respiratory steady-state conditions at rest, the MV̇O2 (7.6-14.2 ml/min/100 g) was measured directly by myocardial blood flow (argon method) and arteriocoronary venous oxygen content difference. MV̇O2 was compared with five indirect indices of MV̇O2. A complex additive parameter consisting of five components of MV̇O2 had the highest correlation with MV̇O2 (r = 0.97), as was also demonstrated in a recent experimental study at maximum changes in hemodynamics and MV̇O2. More easily measurable predictors of MV̇O2 such as tension-time index (r = 0.923), product of mean systolic aortic pressure and square root of heart rate (r = 0.928), pressure-rate product (r = 0.915), and triple product (r = 0.941) were less closely correlated with MV̇O2. The lower correlations of the readily obtainable indices of MV̇O2 are probably related to their failure to incorporate factors such as contractility and ventricular dimensions, which are known to exert an important influence on MV̇O2. The excellent correlation of the hemodynamic additive parameter with MV̇O2 supports the theoretical concept and the implications of the experimental study. The accurate prediction of MV̇O2 is based on adequate measurement of MV̇O2 for the velocity of tension development and maintenance of tension during systolic ejection period, both of which are integrated in the additive index.