Comparison of the effects of nitroprusside and nitroglycerin on coronary size

Nitroglycerin and nitroprusside are known to differ in their relative degree of systemic arterial and venous dilation. Nitroglycerin has been shown to be a potent large-vessel coronary dilator, but the effects of nitroprusside on coronary artery size are unclear. Accordingly, we studied coronary artery angiographic responses to both nitroprusside and nitroglycerin in 12 patients. Diameters Of left coronary artery segments were measured by quantitative angiography before and during an intravenous infusion of nitroprusside and after sublingual nitroglycerin when both drugs were administered in doses adjusted to achieve reductions in aortic pressure. Dilation of the left coronary artery was observed after nitroprusside and after nitroglycerin. Degrees of dilation were similar in the various left coronary artery segments after either nitroprusside or nitroglycerin. In general, segments located more proximally dilated less than those located more distally after either agent. We conclude that both nitroprusside and nitroglycerin are potent dilators of large epicardial and of smaller intramuscular coronary artery segments. The magnitude of dilation of all measured left coronary artery segments appeared remarkably similar with nitroprusside and nitroglycerin given in doses that produced a similar reduction in aortic pressure.