Anaerobic myocardial metabolism

Metabolic changes occurring during coronary insufficiency were studied in ten dogs by progressively reducing the rate of blood flow to the perfused left main coronary artery, while maintaining aortic pressure constant. Seven animals exhibited a net myocardial lactate production at low coronary flows, averaging 2.8 mg/min. The remaining animals showed a decreased lactate uptake which fell from an average 40 to 1.8% at the lowest flows. A rise in left atrial pressure occurred coincident with the alteration of lactate metabolism in all animals. Calculated coronary vascular resistance fell from an average 2.33 to 1.24 units, and in each case reached the minimum value at the onset of the metabolic changes. These results indicate that left ventricular failure, anaerobic myocardial metabolism, and maximal coronary arteriolar dilatation occur at the same time during inadequate myocardial blood flow.