RESUMEN
BACKGROUND: Previous studies suggest that microvascular abnormalities may contribute to the pathogenesis of Chagas' heart disease. Coronary flow reserve (CFR) expressed by the maximum achievable flow relative to baseline flow in the coronary microcirculation, may be useful in identifying patients who may be developing cardiac manifestations of the disease. This study aims to assess the CFR in patients with indeterminate form of Chagas' disease, and also to identify the determinants of CFR. METHODS: Sixty-four asymptomatic patients (37% male; age 49.9 ± 11.5 years) with normal cardiovascular exams classified as in indeterminate form of Chagas' disease underwent transthoracic dipyridamole (0.84 mg/kg in 6 min) stress echocardiography, and were compared with a control group of healthy patients. Coronary flow reserve was assessed on left anterior descending artery using pulsed Doppler as the ratio of maximal peak vasodilation (dipyridamole) to rest diastolic flow velocity. A treadmill exercise test was performed to rule out ischemia. RESULTS: All patients had good functional capacity assessed by exercise testing with peak oxygen consumption (VO2 ) of 28 ± 11 mL/kg per minute, similar to the controls. There were no differences in the echocardiographic parameters of diastolic and systolic left ventricular function and right ventricular function between the patients and controls. Coronary flow reserve was significantly lower in Chagas' disease patients than those in healthy individuals (1.9 ± 0.4 vs. 2.6 ± 0.5; P < 0.001). Several factors were correlated with the CFR, including age, ejection fraction, left ventricular diastolic function, heart rate recovery, and the presence of Chagas' disease. In a multivariate analysis, age and positive serology for Chagas' disease were independent factors associated with the CFR. CONCLUSIONS: Coronary flow reserve was impaired in Chagas' disease patients in the indeterminate form compared with healthy individuals with similar clinical features. Among all variables tested, age and positive serology for Chagas' disease were independent factors associated with the CFR.