Arritmia esforço-induzida em pacientes chagásicos sem cardiopatia aparente e fatores associados à sua ocorrência

Abstract

Chagas disease is a major cause of cardiopathy in Brazil, with great socioeconomic impact. Despite the current control of the transmission through vector and blood transfusions, it is still a serious public health problem due to the significant number of infected individuals who have the potential to develop severe forms. The aim of this study was to evaluate the prevalence and factors associated with the occurrence of ventricular extrasystoles induced by cardiac stress tests on individuals with Chagas disease without apparent heart disease, compared with non-chagasic control subjects. This is a transversal observational study conducted between August 2009 and December 2010, in which 75 asymptomatic individuals with positive serology for T. cruzi, without apparent heart disease and 38 healthy subjects with age and sex similar to the cases were selected. All patients underwent a 12-lead electrocardiogram, analyzed according to standardized criteria for Chagas disease. A conventional echocardiography was done with measurement and evaluation of the ventricular function according to established criteria. All participants were submitted to cardiac stress tests according to the Bruce protocol for assessment of exercise-induced arrhythmia and analysis of other variables such as double product, functional capacity through the maximal oxygen consumption, blood pressure response, and chronotropic response. Tests to evaluate the autonomic function such as the Valsalva manoeuvre and the test of the respiratory sinus arrhythmia were also performed. Furthermore, the patients with positive serology for T. cruzi were submitted to Holter monitoring for 24 hours. They were aged 44.7 ± 8.5 years old, in which 36 were men (48%) and the control subjects were aged 44 ± 9.2 years old in which 22 were men (58%). The total number of isolated supraventricular and premature ventricular contractions during exercise and recovery phase of the cardiac stress tests was higher in cases, as compared to controls. In patients with Chagas disease, there was correlation between the total number of isolated ventricular premature contractions during the tests with the total number of ventricular isolated dynamic electrocardiography (r = 0.47, p <0.001). All conventional echocardiographic parameters used to analyse the diameter, the systolic and diastolic functions of the left ventricle were similar between cases and controls. Five individuals with Chagas disease (7%) presented contractibility deficit in the two-dimensional echocardiogram. There was no association between the number of isolated premature ventricular contractions in the cardiac stress test and the Holter, between chagastic patients disease with segmental changes in the echocardiography. In the test of the respiratory sinus arrhythmia, an index of vagal activity, the ratio between the highest and lowest cardiac exhaling and inhaling intervals was lower in the patients with Chagas disease compared to the non-chagasic controls, correlating with maximum heart rate reached during the cardiac stress test (r = 0.36, p <0.001). It was observed that patients with Chagas disease without apparent heart disease have a higher frequency of exercise-induced arrhythmia, in association with the presence of arrhythmias in Holter and lower values of the vagal indices in the respiratory sinus arrhythmia test