In patients with chronic valvular or myocardial disease, chronic increases in resting ventricular metabolic requirements appear to be met by myocardial hypertrophy rather than by increased myocardial oxygen consumption per unit of mass.
Thirty-eight adults with valvular and/or myocardial disease had heart catheterization with coronary blood flow and myocardial O2 consumption (MVO2) per 100 g measured by the nitrous oxide washout technique. Quantitative biplane angiocardiography was performed to assess left ventricular volume, mass, ejection fraction and work. Left ventricular efficiency was calculated from work, MVO2/100 g and mass. Efficiency ranged from 4 to 40% and was normal in some patients with severe ventricular pressure-volume work overloads. Total left ventricular MVO2 ranged up to 461 ml/min. Neither total MVO2 nor MVO2/100 g was significantly related to ventricular work, ejection fraction, or tension-time index. These data suggest 1) a relationship between left ventricular efficiency and myocardial function in chronic valvular or myocardial disease, 2) that efficiency may be normal in hypertrophied ventricles, and 3) that chronic increases in resting ventricular metabolic requirements are met by hypertrophy rather than by increased MVO2/100 g.
Baxley et al. (Fri,) studied this question.