Application of nitrates in coronary artery disease and acute myocardial infarction

Nitroglycerin and its derivatives are among the most potent drugs to treat angina pectoris. The compounds relax all smooth muscle cells by stimulating the soluable guanylate cyclase. The clinical application takes advantage of the different sensitivities of the vascular smooth muscles (veins > arteries > arterioles) to nitrates. Selective vasodilation of capacity veins and coronary arteries leads to reduced myocardial oxygen consumption and improved myocardial perfusion. Hypotension due to effective dilation of resistance arteries limits the antianginal effects because of reduced coronary perfusion. Treatment of symptoms in stable angina is well established and unquestioned as long as the dose regimen avoids tolerance; however, there is no evidence of reducing mortality with nitrates in these patients. In acute coronary syndromes such as unstable angina pectoris and acute myocardial infarction nitrates, but not nitroprusside, can be applied safely to relief symptoms and to treat vasospasm, if the dose is titrated to avoid hypotension. Recent large multicenter trials (GISSI-3, ISIS-4) have not confirmed the postulate derived from previous studies, that nitrates reduce the mortality from acute myocardial infarction within the first month.