The role of endothelial dysfunction in development of myocardial ischemia in patients with ischemic heart disease and unchanged or minimally changed coronary arteries

Myocardial perfusion after intracoronary acetylcholine was studied in 23 patients with coronary risk factors and unchanged or minimally changed coronary arteries. Acetylcholine was infused in the left coronary artery in 3 incremental concentrations (5x10(-7), 5x10(-6) and 5x10(-5) mmol/l, each for 2 min). Changes of diameter of proximal and median segments of left anterior descending and circumflex coronary arteries were evaluated by repetitive contrast angiography. Technetium-99m-MIBI was injected intravenously either simultaneously with the last dose of acetylcholine or when clinical or ECC sign of ischemia appeared. According to results of scintigraphy patients were divided into 2 groups: with (n=12) and without (n=11) transitory myocardial perfusion defects. All patients with perfusion defects had alterations of endothelium-dependent vasodilation evidenced by vasoconstriction (n=10) or lack of dilation (n=2) in response to intracoronary acetylcholine while only 5 of patients without transitory myocardial perfusion defects produced signs of disturbed endotheliumdependent vasodilatation. These results show that in patients with unchanged or minimally changed coronary arteries myocardial ischemia can be caused by disturbances of endothelium-dependent vasodilation.