Unusual vasomotor coronary arterial responses after nitroglycerin

Angiographic evidence of unusual vasomotor responses occurred in two patients after administration of sublingual nitroglycerin. In these patients, right coronary arterial segments that appeared angiographically normal before the administration of nitroglycerin showed narrowing after nitroglycerin. Adjacent segments in each of these vessels, as well as the other coronary arteries, dilated as expected. Both patients remained asymptomatic. Repeated administration of nitroglycerin did not alter the anglographic appearance of these vessels. No reason for the localized reduction of coronary arterial diameter was apparent. The possibility that nitroglycerin was associated with these unusual changes is an additional argument against the routine administration of nitrates before coronary arteriography.