Intracoronary administration of isosorbide dinitrate induced severely slow flow and transient ST-segment elevation.

Nitroglycerin is one of the most widely used drugs in the treatment of angina. However, nitroglycerin fails to relieve angina in patients with syndrome X who have microvessel dysfunction. Microvessel function is impaired in several diseases. In this article, the authors report that despite normal coronary angiograms at control, intracoronary administration of isosorbide dinitrate induced severe coronary slow flow and transient ST-segment elevation with mild chest pain in a patient with congestive heart failure. The authors speculated that functional stenosis and a delay in the dilatation of microvessels less than 100 microm in diameter because of their dysfunction resulted in a severely slow flow after intracoronary administration of isosorbide dinitrate.