Symptoms of myocardial ischemia, such as chest pain (sometimes with anginal features), acute myocardial infarction, and segmental wall motion abnormalities (including left ventricular apical aneurysm), frequently occur in patients with Chagas' heart disease. Because these clinical findings occur in the presence of normal coronary arteries, it is possible that an abnormality of the coronary vascular reactivity could be present in these patients. Therefore the current study was undertaken to determine whether endothelium-dependent coronary vasodilation is abnormal in Chagas' heart disease. Coronary endothelial function was assessed by infusing the endothelium-dependent vasodilator acetylcholine (10(-8) to 10(-6) mol/L) and the endothelium-independent vasodilator adenosine (10(-4) mol/L) into the left anterior descending coronary artery of nine patients (age 43 +/- 4 years) with Chagas' heart disease. Coronary blood flow was measured with a Doppler flow velocity catheter and by quantitative coronary cineangiography. The left ventricular ejection fraction was 39% +/- 5%; eight patients had a left ventricular apical aneurysm; and one had an area of anteroapical hypokinesis. An impairment of the endothelium-dependent coronary vasodilation was demonstrated by a reduction in coronary blood flow of 41.2% +/- 12.8% produced by the infusion of acetylcholine at 10(-6) mol/L and by a blunted but preserved increase in coronary blood flow of 114.6% +/- 65.0% with the infusion of adenosine at 10(-4) mol/L (p = 0.03). In conclusion, patients with Chagas' heart disease have an abnormality of the coronary endothelium-dependent vasodilation, and this abnormality may play a role in their chest pain syndrome and in the development of segmental wall motion abnormalities.