The standard-deviation of all consecutive normal interbeat intervals in 24h (24h SDNN) was employed to assess heart rate variability. Normal cut-off point was defined at >=100ms. During follow-up, 24h ambulatory ECG were performed at the discretion of attending physician's judgment in order to assess cardiac rhythm and arrhythmia. One trained specialist blind to Los Andes classification groups analyzed all tape recordings immediately after their acquisition.