Method: At entry, as well as at the end of the study all subjects underwent a cardiopulmonary exercise testing (estimation of aerobic capacity-VO2peak), an echocardiographic study (LV ejection fraction -LVEF evaluation), an ambulatory 24-hour Holter monitoring for cardiac autonomic nervous system activity evaluation by time- and frequency- domain heart rate variability (HRV) calculation (measurement of SDNN, mean RR and low to high frequency ratio-LF/HF), a signal-averaged ECG (late potentials-LP documentation) and a submaximal exercise test for microvolt-T-wave alternans (TWA) detection.