MYOCARDIAL ANAEROBIC METABOLISM DURING ISOPRENALINE INFUSION IN A CYANOTIC ANIMAL-MODEL - POSSIBLE CAUSE OF MYOCARDIAL DYSFUNCTION IN CYANOTIC CONGENITAL HEART-DISEASE

Summary: Mongrel dogs were made acutely cyanotic by anastamosis of the inferior vena cava to the left atrium and measurements of high fidelity left ventricular pressure, arterial pressure, blood gases, and myocardial lactate arteriovenous differences were determined before pacing, with atrial pacing at a rate of approximately 240 per minute, and during an infusion of isoprenaline to increase myocardial oxygen demands. The animals were divided into two groups on the basis of the arterial PO2 during isoprenaline: acyanotic or control dogs (n =4, PO2, ≥ 6.7 kPa [50 mmHg], x = 52) and cyanotic dogs (n =5, PO2, ≤ 4.7 kPa (35 mmHg), x = 32). Myocardial lactate arterio-venous difference showed no significant changes in the control dogs with pacing or isoprenaline, but myocardial lactate production occurred in all five cyanotic dogs with isoprenaline infusion. These studies demonstrate that myocardial anaerobic metabolism can be produced during times of stress with isoprenaline infusion in a cyanotic animal model at systemic oxygen levels that can occur clinically.