Cardiacautonomic modulation and long-term use of amiodarone in patients with chronic Chagasic cardiopathy.

Abstract

Patients with chronic Chagas cardiopathy (CCC), which may be associated with cardiac arrhythmias, frequently use amiodarone, an antiarrhythmic drug that, experimentally, appears to modulate the cardiac autonomic function. The present cross-sectional observational study aimed to evaluate autonomic cardiac modulation in patients with CCC undergoing chronic amiodarone therapy. Three groups were investigated: Group 1 included patients with CCC not treated with amiodarone (n=27); Group 2 included patients with CCC with prolonged use (at least 6 months) of amiodarone (n=16); and Group 3 included non-Chagasic control patients (n=23). All patients underwent a complete clinical and laboratory assessment, followed by autonomic function tests, consisting of a basal continuous electrocardiogram in the resting supine position for 10 minutes, followed by a change the orthostatic posture for a further 5 minutes. Heart rate variability (HRV) parameters (median and interquartile interval) were quantified using linear methods in the time- and frequency-domains (autoregressive spectral analysis) and nonlinear methods, including symbolic analysis. Patients with CCC using amiodarone had changes in HRV suggestive of an offset in the sympatho-vagal balance with a vagal modulation predominance (normalized HF, 49.7[27.4] vs 31.1[22.8] [P<0.05]; and percentage 2V, 40.1 [14.6] vs 21.5 [13.4] [P<0.05] vs untreated CCC group). These changes were further accompanied by increases in parameters indicative of greater complexity of HRV. The deviation in the sympatho-vagal balance and the increase in the complexity of HRV strongly suggest that amiodarone may have a cardioprotective effect, in addition to its antiarrhythmic effects, which could increase the survival of these patients.