Provocation of Microvessel Spasm by Low-Dose Acetylcholine in Patients with Suspected Coronary Artery Disease

Abstract

Endothelial dysfunction plays an important role in the pathogenesis of cardiac syndrome X, and intracoronary low-dose acetylcholine infusion is a widely used diagnostic modality for studying the coronary artery endothelial function. The authors herein report 2 cases of cardiac syndrome X with coronary artery endothelial dysfunction and microvessel spasm. The findings of non invasive testing were positive for ischemia. Coronary angiograms appeared entirely normal in both cases. However, the intracoronary infusion of low-dose (1.5-15 µg/minute) acetylcholine demonstrated an impairment of the coronary blood flow response and consequently provoked an ST-segment elevation in an electrocardiogram. The coronary angiograms showed no spasm in the epicardial arteries. These patients are thus suggested to have cardiac syndrome X with microvessel spasms associated with coronary artery endothelial dysfunction.