The current status of nitrites in the treatment of coronary artery disease

Abstract

The nitrites remain the cornerstone of treatment in the anginal syndrome despite unresolved questions regarding their mechanism of action. Although increase in coronary blood flow probably occurs in all subjects, this change is transient; and the effectiveness of nitrites in angina may be related to preferential effects on collateral vessels in which an increase of flow may not be reflected in total coronary flow as usually measured. The beneficial effects of nitrites in angina might also be explained on the basis of a reduction in left ventricular work and therefore oxygen requirements. The newer nitrates have not displaced the use of nitroglycerin in the treatment or prevention of acute anginal attacks. The question of whether chronic usage of nitrites can enhance the development of coronary collaterals in patients with angina remains unanswered. Although nitrites have traditionally been felt to be contraindicated in the presence of acute myocardial infarction, experiments involving coronary artery obstruction with ischemia have suggested that collateral blood flow may be enhanced by these agents if arterial blood pressure does not decline markedly. A number of hemodynamic studies have demonstrated enhanced left ventricular function after nitrites, supporting the clinical experience of their effectiveness in relieving paroxysmal nocturnal dyspnea. Further studies of a quantitative physiological nature are needed to evaluate the effects of nitrites on regional blood flow and metabolism within the myocardium, particularly in the presence of ischemia.