Comparison of coronary endothelial dynamics with electrocardiographic and left ventricular contractile responses to stress in the absence of coronary artery disease

Coronary artery endothelial dysfunction has been proposed as a cause of myocardial ischemia and symptoms in patients with angina-like chest pain despite normal coronary angiograms, especially those with ischemic-appearing ST-segment depression during exercise (syndrome X). We measured coronary vasomotor responses to acetylcholine (3 to 300 μg/min) in 42 patients (27 women and 15 men) with effort chest pain and normal coronary angiograms who also had normal electrocardiograms and echocardiograms at rest. All patients underwent treadmill exercise testing and measurement of systolic wall thickening responses to dobutamine (40 μg/kg/min) during transesophageal echocardiography. There were no differences in the acetylcholine-stimulated epicardial coronary diameter (+5 ± 13% vs + 1 ± 13%, p = 0.386) and flow (+179 ± 90% vs +169 ± 96%, p = 0.756), or in the systolic wall thickening responses (+134 ± 65% vs +118 ± 57%, p = 0.445) from baseline values in the 12 syndrome X patients compared with the 30 patients with negative exercise test results. In patients in the lowest quartile of coronary flow responses to acetylcholine, dobutamine increased systolic wall thickening by 121 ± 73%; 3 had ischemic-appearing ST-segment depression during this stress. This contractile response to dobutamine was no different than the increase in systolic wall thickening (129 ± 48%, p = 0.777) in patients in the highest quartile of coronary flow responses, 3 of whom also had ischemic-appearing ST-segment depression during this stress. Thus, coronary endothelial dysfunction in the absence of coronary artery disease does not account for ischemic-appearing ST-segment depression in patients with chest pain despite normal coronary angiograms. Further, coronary endothelial dysfunction is not associated with myocardial contractile responses to stress consistent with myocardial ischemia.