Coronary stenosis dilation by low dose intravenous nitroglycerin

In a randomized double-blind study, 40 patients with coronary heart disease received either 0.025 mg nitroglycerin or placebo intravenously. Before and 2-3 min after injection, the aortic and left ventricular pressures were recorded and coronary angiography was performed. Mean heart rate, systolic and diastolic aortic pressure, left ventricular filling pressure and the pre- and poststenotic coronary artery diameters, as well as the diameters of representative distal coronary artery segments showed no significant changes. Coronary artery stenosis diameters remained unchanged after placebo (1.01 +/- 0.5 to 1.13 +/- 0.49 mm; n.s.) but increased significantly after nitroglycerin from 1.15 +/- 0.68 to 1.32 +/- 0.73 mm (P less than 0.01). Since it has been demonstrated, on the other hand, that the same dose of nitroglycerin reveals antianginal activity, it can be hypothesized from these results that dilatation of coronary stenoses plays an important role in the antianginal action of nitroglycerin. Strong haemodynamic effects do not appear to be a prerequisite of the beneficial effects of nitroglycerin.