Myocardial Metabolism in Progressive Muscular Dystrophy

Abstract

Myocardial metabolism was studied in 11 patients with progressive muscular dystrophy. Coronary blood flow was measured in four, the cardiac output in six patients. The blood concentrations of oxygen, glucose, inorganic phosphate, pyruvate, and lactate, and the serum activities of malic dehydrogenase and aldolase were determined in simultaneously drawn coronary sinus and arterial blood samples. The cardiac outputs were elevated in all patients. Myocardial extractions of pyruvate and lactate were negative in two patients. Inorganic phosphate concentrations in blood were elevated. Malic dehydrogenase and aldolase were released by the heart in several patients. Differences in oxidation-reduction potential between arterial and coronary venous blood were positive, suggesting glycolysis in the heart muscle. This was accompanied by increased myocardial extraction of glucose. Apparently aerobic glycolysis occurred, since sufficient oxygen was present to account for all glucose extracted. Stimulation of glycolysis by inorganic phosphate was suggested by the relationship between the elevated inorganic phosphate concentration in blood and the myocardial glucose extraction. This suggests the possibility of uncoupling of oxidative phosphorlyation in the myocardium.