Avaliação da reserva de fluxo coronariano na forma indeterminada da doença de Chagas

Abstract

Introduction: Chagas disease is an important cause of heart failure in Brazil, with high socio-economic impact. Most infected individuals are in the indeterminate form, with the potential for developing heart disease. Previous studies have shown that there are changes in coronary microcirculation in Chagas disease, which is a mechanism involved in the genesis of heart disease. The coronary flow reserve (CFR), which expresses the coronary vasomotor function, is related to the microcirculation, endothelial and autonomic function. Early detection of microcirculatory changes can identify subgroups of asymptomatic patients in the indeterminate who are at risk of progression to heart disease. Objectives: The purpose of this study was to evaluate the coronary flow reserve in patients with Chagas disease in the indeterminate form, compared to a healthy control group. Additionally, we aimed to establish the main determinants of changes in the CFR in Chagas disease. Methods: This is an observational study, conducted between March 2010 and September 2012, which included 64 patients with a mean age of 49.9 ± 11.5 years, 37% men. Patients eligible for the study should have two positive tests for T. cruzi, asymptomatic and without changes in cardiovascular clinical examination, electrocardiogram, chest X-ray, barium enema and esophagram, classified as indeterminate form. A control group of 28 healthy subjects with similar age and gender of cases were selected for comparison of all variables. Patients underwent clinical examination and after documentation of all exams (performed at most 3 months before the clinical evaluation), were referred for transthoracic stress echocardiography with dipyridamole. The RFC was obtained by pulsed Doppler, measuring the peak diastolic flow baseline and after dipyridamole infusion (0.84 mg / kg in 6 minutes) in the distal left anterior descending coronary artery. A random sample of 15 individuals was selected to test the interobserver and intraobserver variability of FRC. Results: The patients were similar to controls in relation to body surface area, blood pressure, basal heart rate (HR) and the mean HR in 24- hour Holter. The maximum HR and the HR in the first minute of recovery in exercise testing was higher in cases than in controls, with no difference in VO2 peak and exercise time. Echocardiographic parameters including heart chamber dimensions, systolic and diastolic function were not different between cases and controls. The RFC was significantly lower in patients with Chagas disease compared to the control group (1.9 ± 0.4 vs. 2.6 ± 0.5, p <0.001). Several factors correlated with CFR in the univariate analysis, including age, echocardiographic variables of left ventricular systolic and diastolic function, right ventricular systolic function, HR in the 1 ° minute of recovery in exercise test and the absolute reduction of HR in the 1° minute of recovery. In multivariate analysis, age and positive serology for Chagas disease were independent factors associated with the RFC. Conclusions: The study demonstrated that coronary flow reserve is impaired in patients in the indeterminate form of Chagas disease when compared to a group of healthy subjects with similar age and sex to the cases. The age and positive serology for Chagas disease were independent factors associated with changes in the RFC.