SAECG was acquired in sinus rhythm with a Predictor-IIc equipment (ART Inc., Fitchburg, Massachusetts, USA) using modified XYZ Frank orthogonal leads and QRS-triggered coherent-averaged up to the noise level of 0.3 microvolt. SAECGs were analyzed in both time and frequency domains by an independent observer blinded to the study patients information. After signal average ECG acquisition, time domain analysis was carried out on vector magnitude (VM), using a bidirectional 4th order 40 Hz to 250 Hz band-pass Butterworth filter. The variables extracted from VM were: duration of VM (DUR [ms]), root-mean-squared voltage of last 40ms of VM (RMS40[microvolt]) duration of potentials below 40 microvolt at the terminal portion of VM (LAS40[ms]). Due to the presence of bundle branch block as a common finding in Chagas disease, normal cut-off point for DUR was defined at >150ms.