[Endothelial dysfunction in ischemic syndromes].

Several studies have shown evidence of the key role of the endothelium in modulating the tone of epicardial coronary vessels, in the different manifestations of coronary artery disease. Recently, the role of endothelium-dependent vasodilation has been focused, because clinical observations have suggested that myocardial ischemia might be caused or aggravated by inappropriate vasoconstriction of resistance vessels. An abnormal endothelium-dependent vasodilation, either of epicardial and of coronary microvasculature, has been documented in patients with syndrome X and in patients with history of hypertension and left ventricular hypertrophy. Vasoconstriction of the small coronary vessels is probably the mechanism underlying the impaired increase of coronary blood flow during atrial pacing and the wide variations of the ischemic threshold in some patients with chronic stable angina. In patients with variant angina, the endothelial function seems abnormal only in the conductance vessels. It is likely that the endothelial dysfunction of the small coronary arteries be present in many clinical situations in which a discrepancy between a mild atherosclerosis of epicardial coronary artery and signs of ischemia exists, as it has been observed early after successful angioplasty and after coronary artery reperfusion during acute myocardial infarction.