Effects of metabolic and pharmacologic interventions on myocardial infarct size following coronary occlusion

A number of hemodynamic, pharmacologic, and metabolic interventions were found to change the extent of acute ischemic injury of the myocardium and subsequent necrosis following experimental coronary artery occlusion. Reduction in myocardial damage occurred by decreasing myocardial oxygen demands (beta-adrenergic blocking agents, intra-aortic balloon counterpulsation, nitroglycerin, decreasing afterload in hypertensive patients, inhibition of lipolysis, and digitalis in the failing heart); by increasing myocardial oxygen supply either directly (coronary artery reperfusion or elevating arterial pO2), or through collateral vessels (evevation of coronary perfusion pressure by alpha adrenergic agonists, intra-aortic balloon counterpulsation); or by increasing plasma osmolality (manitol, hypertonic glucose); presumably by augmenting anaerobi metabolism (glucose-insulin-potassium, hypertonic glucoxe insulin potassium, hypertonic glucose); by enhancing transport to the ischemic zone of substrates utilized in energy production (hyaluronidase); by protecting against autolytic and heterolytic damage (hydrocortisone, cobra venom factor, aprotinin). Augmentation of myocardial ischemic damage occurred as a consequence of increasing myocardial oxygen requirements (isoproterenol, glucagon, ouabain, bretylium tosylate, tachycardia); by decreasing myocardial oxygen supply either directly (hypoxia, anemia), through reduction of collateral flow (hemorrhagic hypotension, minoxidil), or by decreasing substrate availability (hypoglycemia). Pilot studies have been carried out in patients with hyaluronidase, nitroglycerin intra-aortic balloon counterpulsation, beta-blocking agents and Arfonad and have shown that these interventions may also reduce myocardial damage, which suggests that the concept of reduction in infarct size following coronary occlusion is applicable clinically.