[Coronary-dilating effect of minimal doses of nitroglycerin]

A previous study verified the antianginal efficacy of 0.025 mg nitroglycerin without it having any effect on heart rate and blood pressure. In a randomized double-blind study, 40 patients with coronary heart disease received intravenously either 0.025 mg nitroglycerin or placebo. Before and 1-2 min after injection, the aortic and left ventricular (n = 20) pressures were recorded and coronary angiography performed. Mean heart rate, systolic and diastolic aortic pressure, left ventricular filling pressure and the pre- and poststenotic diameter of the coronary arteries, as well as the diameter of a distal coronary artery segment, showed no significant changes (p greater than 0.05). The stenotic segment diameter of the coronary artery remained unchanged after placebo administration (1.01 +/- 0.5 to 1.13 +/- 0.49 mm; p greater than 0.05) but increased significantly after the injection of nitroglycerin (from 1.15 +/- 0.68 to 1.32 +/- 0.73 mm; p less than 0.01). These results support the hypothesis that dilatation of coronary stenoses is an important aspect of the antianginal action of nitroglycerin. This may have practical consequences in the treatment of patients with angina and low blood pressure or severe headaches after the administration of conventional doses of nitroglycerin.