Impaired Endothelium-Dependent Vasodilation of Coronary Resistance Vessels Is Associated With Exercise-Induced Myocardial Ischemia

Background The release of endothelium-derived relaxing factors has been shown experimentally to be of pivotal importance for the maintenance of coronary blood flow during increased demand. In humans with coronary atherosclerosis, endothelial vasodilator dysfunction is not confined only to epicardial conductance vessels but may also extend into the coronary microcirculation. We therefore tested the hypothesis that endothelial vasodilator dysfunction of the coronary resistance vasculature is associated with myocardial ischemia during exercise in patients without hemodynamically significant epicardial artery stenoses. Methods and Results Coronary vasodilator function was assessed by subselective infusion of the endothelium-dependent dilator acetylcholine (0.036 to 3.6 μg/mL) and the endothelium-independent dilator papaverine (7 mg). Coronary blood flow responses were evaluated by intracoronary Doppler flow velocity recordings and quantitative angiography. Exercise-induced myocardial perfusion was determined ...