1. Department of Clinical Internal, Anesthesiologic and Cardiovascular Sciences, Sapienza University of Rome , 00161 Rome , Italy
2. Cardiology Department, Luigi Sacco Hospital , 20157 Milan , Italy
3. St. David’s Medical Center, Texas Cardiac Arrhythmia Institute , Austin, TX 78705 , USA
4. Cardiology Department, Policlinico Casilino , 00169 Rome , Italy
5. Cardiology Division, Giovan Battista Grassi Hospital , Via Gian Carlo Passeroni 28, 00122 Rome , Italy