[5-isosorbide mononitrate at rest and on exercise in coronary heart disease: acute and long-term effect]

Haemodynamic effects of 5-isosorbide mononitrate (5-ISMN) were studied at rest and on exercise in 31 patients with angiographically confirmed coronary heart disease. A decrease in arterial blood pressure and mean pulmonary artery pressure without significant change in heart rate, cardiac output and stroke volume occurred both at rest and on exercise after 20 mg of 5-ISMN to 12 patients. Administration of 50 mg 5-ISMN to 19 patients achieved greater decrease in mean pulmonary artery pressure; cardiac output and stroke volume were highly significantly reduced at rest, while on exercise both cardiac output and stroke volume remained unchanged. Ten patients, in whom after a single dose of 50 mg 5-ISMN the mean pulmonary artery pressure at rest and on exercise had decreased 28% and 45%, respectively, with a definite rise in exercise tolerance, repeat acute administration of a single dose of 50 kmg 5-ISMN produced a fall in mean pulmonary artery pressure at rest by 20% after 50 mg three times daily for four weeks. On exercise the fall was only 14% below the control levels before treatment. In addition, exercise tolerance was reduced. These results indicate that acute administration of 5-ISMN at rest and on exercise decreases cardiac work load. But on chronic administration of high doses, tolerance to the drug may develop.