Measurements: At entry and the end of the study, in all participants aerobic capacity (VO2peak) and left ventricular ejection fraction (LVEF) were estimated, late potentials and T-wave alternans were detected and heart rate variability was calculated. Specifically, from the 24-h Holter monitoring the standard deviation of all the normal R-R intervals (SDNN), the mean R-R intervals (mean RR), the low (LF) and high (HF) frequency components of the autoregressive power spectrum of the NN intervals and their ratio (LF/HF) were recorded.