NUTRITIONAL CIRCULATION IN HEART .2. A REAPPRAISAL OF EFFECT OF NITROGLYCERIN ON MYOCARDIAL HEMODYNAMICS, OXYGEN CONSUMPTION AND NUTRITIONAL BLOOD FLOW IN ISOLATED SUPPORTED HEART PREPARATION

The effect of intracoronary administration of 2 to 80 μg doses of nitroglycerin (GTN) was investigated in the isovolumic supported dog heart preparation. In the beating heart preparation, GTN produced a fall in coronary artery perfusion pressure (CAPP), a decrease in left ventricular systolic pressure (LVSP) and an increase in the coronary sinus oxygen tension (VpO2). The increase in VpO2 was primarily due to a decreased myocardial oxygen consumption and not due to a redistribution of blood through A-V shunts. This conclusion is reached on the basis of the observations that GTN had no effect on 86Rb clearance by the myocardium. In the myocardial homogenate preparation, GTN produced a dose-dependent decrease in the rate of myocardial oxygen utilization in the dosage range of 1 × 10-7 to 1 × 10-3 molar/ml. These observations suggest that GTN exerts a direct effect upon myocardial work and oxygen consumption. In the fibrillating heart preparation, GTN produced a slightly greater decrease in CAPP. There was also an increase in the VpO2, but GTN concurrently decreased 86Rb clearance in these experiments. © 1969.