Regional myocardial metabolism during subtotal and total coronary artery occlusion

Regional myocardial metabolism was examined by means of coronary venous sampling in dogs having acute nonsimultaneous occlusions of the left anterior descending (LAD) and circumflex (CIRC) coronary arteries. Regional coronary venous metabolic sampling was not found to separate ischemic from nonischemic myocardium in LAD occlusion and did so imperfectly in isolated CIRC occlusion. Myocardial metabolic consequences of subtotal and total coronary artery occlusion were compared in dogs during LAD and CIRC occlusion and in human subjects with subtotal and total anterior coronary artery occlusion. In spite of ECG evidence of greater myocardial ischemia during total coronary artery occlusion in the dog, transmyocardial metabolic changes were more consistent during subtotal occlusion. Human subjects stressed during cardiac catheterization exhibited a similar apparent paradox. This suggests variable coronary venous washout from ischemic myocardium during total coronary artery occlusion and, in humans, may also reflect the presence of scar tissue. Caution is advised when interpreting myocardial metabolic information in the presence of total coronary artery occlusion, since underestimation of the extent of myocardial ischemia is more likely than with an occlusion of lesser degree.