Primary prevention of death from ischemic heart disease requires further understanding of the pathogenesis of this disorder. Cellular defects of cholesterol metabolism may be more significant markers that serum lipid levels for the identification and treatment of atherosclerotic risk. Coronary spasm has been shown to be an important cause of ischemia in the presence and absence of atherosclerotic lesions. Careful manipulation of physiologic variables with vasodilator agents during cardiopulmonary bypass can substantially alter the myocardial oxygen supply-demand relation, thereby minimizing ischemic injury. The cellular basis for loss of mechanical function during ischemia and the factors that determine irreversible injury are yet unknown.