Endothelin. Key to coronary vasospasm?

In 1959, Prinzmetal and colleagues described a new form of chest pain that developed at rest and very often occurred in the early morning hours.12 The pain was associated with ST segment elevations in the electrocardiogram and relieved by nitroglycerin. They named the syndrome "variant angina" and suggested that it was caused by a spasm of a major epicardial coronary artery. Subsequently, coronary spasm has been documented angiographically in patients with variant angina.3-7 In addition, coronary vasomotion has been recognized as an important factor in the pathogenesis of most ischemic coronary syndromes.8'9 Although the phenomenon has been well characterized clinically and angiographically, the cause of coronary spasm remains enigmatic. Moreover, it even appears uncertain whether all increases in coronary vascular tone occurring in acute ischemic syndromes can be explained by a single factor or represent a heterogenous entity ranging from normal coronary vasomotion in a narrowed vascular segment to "true spasm" (i.e., variant angina) with total or near-total occlusion of an angiographically normal or mildly atherosclerotic coronary artery.8