Myocardial oxygen consumption in chronic heart disease: role of wall stress, hypertrophy and coronary reserve.

The relations between left ventricular mass, mass to volume ratio, systolic wall stress and myocardial oxygen consumption were analyzed in 187 patients with chronic heart disease. The degree of left ventricular hypertrophy is determined by mass, the mass to volume ratio, and pressure and, hence, systolic wall stress. For each condition an inverse relation exists between mass to volume ratio and peak systolic wall stress. In chronic heart disease at least two types of inappropriate left ventricular hypertrophy may occur: (1) low stress hypertrophy with an increased mass to volume ratio, normal left ventricular function and normal or reduced oxygen consumption (MVO₂), whereas (2) high stress hypertrophy has a normal or low mass to volume ratio, impaired left ventricular function and an increased MVO₂. The range of systolic wall stress was 100 to 450 × 10³, dynes/cm² and reflects the stress that could be altered by inotropic interventions and changes in systolic pressure. A similar reserve capacity is present for both the metabolic and the coronary reserves. Total left ventricular oxygen consumption is related to total left ventricular mass. This relation is influenced by the degree of viability of left ventricular mass, by the mass to volume ratio and by inotropic interventions. Left ventricular oxygen consumption per viable mass unit (MVO₂) is significantly correlated with the systolic force per unit cross-sectional area of the left ventricular wall, that is, to left ventricular systolic wall stress.It is concluded that peak systolic wall stress represents one of the major determinants of myocardial oxygen consumption and of ventricular performance. It closely relates to the appropriateness of left ventricular hypertrophy, which may be defined by the relation between systolic pressure, mass to volume ratio and peak systolic wall stress.