[1] S Croce Hosp, Dept Cardiac Surg, I-12100 Cuneo, Italy
[2] Ist Super Sanita, Natl Ctr Epidemiol Surveillance & Hlth Promot, I-00161 Rome, Italy
[3] IRCCS Policlin S Donato, Unit Cardiac Surg & Translat Res, San Donato Milanese, Italy
[4] Reg Hlth Serv, Dept Epidemiol, Rome, Italy
[5] Univ Milan, IRCCS Policlin S Donato, Unit Cardiac Surg, Milan, Italy