Oxygen metabolism and oxygen debt repayment after myocardial ischemia

Abstract

Coronary blood flow, myocardial oxygen usage, and coronary venous lactate and pyruvate concentrations before and after release of left coronary or left circumflex artery occlusions (10–120 sec) were studied in anesthetized, open-chest dogs. Flow and oxygen theoretical debts were calculated from control blood flow and oxygen usage and compared to the repayments. Flow debts were usually overpaid for all durations of occlusion. Oxygen debts were repaid with an average excess of 1.0 and 3.5 cc after 15 and 30 sec but with a deficit of 0.4 cc for 10-sec left coronary artery occlusions. Excess lactate, as a measure of oxygen debt, was present after 50% of the 30-sec left coronary artery occlusions and after all of the 120-sec circumflex artery clampings. It was demonstrated that ischemia stimulates blood flow and myocardial oxygen consumption and increases oxygen availability. Results indicate that the myocardium can tolerate only brief periods of arterial occlusion but can develop and repay small oxygen debts.