Evidence of endothelial dysfunction of epicardial coronary arteries in patients with immunohistochemically proven myocarditis

Background Recent reports indicate that myocarditis can be associated with acute myocardial ischemia and even myocardial infarction in patients with normal arteriograms. We therefore tested the hypothesis that patients with biopsy-proven myocarditis have endothelial dysfunction despite angiographically smooth epicardial coronary arteries. Methods and Results Graded concentrations of the endothelium-dependent vasodilator acetylcholine (10 -6 to 10 -4 mol/L) and for comparison, the non-endothelium-dependent vasodilator nitroglycerin (0.3 mg intracoronary), were infused into the left coronary arteries of 18 patients (mean age 47 ± 9 years, 8 women and 10 men) with biopsy-proven myocarditis but without angiographically demonstrable coronary artery disease. Vascular responses were analyzed by quantitative coronary angiography. Three patients had an intact vasodilator response to acetylcholine concentrations of up to 10 -4 mol/L in all segments of the left coronary artery, with a mean dilatation of +9.9% ± 2%. In contrast, paradoxical constriction by acetylcholine occurred in 9 patients, who showed a mean change in coronary artery diameter of –11% ± 3%. Six patients had no significant change in any segments in response to acetylcholine (–2.5% ± 4%). There was a significant inverse correlation between the number of T-lymphocytes in the myocardium and the response of the epicardial coronary arteries to acetylcholine (Pearson correlation coefficient –0.49, P = .03). Conclusions It can be assumed that the process of myocarditis is associated with impairment of endothelium-dependent vasodilation in response to acetylcholine in most patients. Vasoconstriction in the presence of acetylcholine in myocarditis is likely to reflect an abnormality of endothelial function. Endothelial dysfunction of coronary arteries may explain the occurrence of myocardial ischemia in patients with myocarditis. (Am Heart J 1998;136:389-97.)