ABSTRACT
392The interaction between regional and global myocardial function, oxygen consumption, and energy production was examined in the left ventricle during pacing, isoproterenol infusion, hypopneic respiration, and noradrenaline infusion. Regional myocardial work was estimated using tension and length recording, and external work from aortic pressure and flow measurement. Coronary sinus blood flow as well as tissue blood flow (microspheres and thermistor techniques) were measured, together with estimation of intracellular oxygen balance by a NADH fluorescence technique. Regional and coronary sinus hemoglobin O2 saturations were determined microspectrophotometrically and by blood gas analysis, respectively. Myocardial O2 consumption and utilization of glucose, pyruvate, lactate, and free fatty acids were estimated. It was found that changes in both regional and global MVO2 closely followed those observed in regional work and left ventricular work, but not external cardiac work. Isoproterenol increased regional work more than regional MVO2, but decreased external work. Noradrenaline increased the proportion of ATP produced from fatty acids as compared with carbohydrates. Hypopneic respiration significantly increased oxygen consumption and substrate utilization, without elevating cardiac work. NADH redox levels were not always correlated with the measured supply/demand data.
