Parasympathetic impairment in the preclinical stage of chronic Chagas disease.

Dear Editor, We have read with great interest the paper by Vasconcelos and Junqueira-Júnior1 who showed that parasympathetic and sympathetic abnormalities occur in patients with chronic Chagas heart disease with no left ventricular systolic dysfunction. These abnormalities were observed in heart rate variability in the time and frequency domain. They concluded that “it is improbable that the marked cardiac autonomic dysfunction can merely be a phenomenon secondary to slight ventricular mechanic disturbance”. We agree. We have demonstrated that only parasympathetic impairment can be observed in heart rate variability in the frequency domain of patients with chronic Chagas disease with no left ventricular systolic dysfunction2. We studied 97 patients, the left ventricular ejection fraction being similar in patients with and in those without parasympathetic impairment. Nonetheless, 8 (8%) of 97 patients with no electrocardiographic abnormality in the 12-lead electrocardiogram and no left ventricular systolic dysfunction at echocardiography had parasympathetic impairment. By contrast, sympathetic derangement was not observed in any of the patients with normal 12-lead electrocardiogram and echocardiogram. However, in patients with chronic Chagas heart disease, as observed in the study by Vasconcelos e Junqueira-Júnior, the proportion of sympathetic and parasympathetic dysfunction was similar to that found in our study.