1. Department of Cardiothoracic Surgery, First Affiliated Hospital of Chengdu Medical College, Chengdu, Sichuan 610500, P.R. China
2. Department of Cardiothoracic Surgery, Chengdu Fifth People's Hospital, Chengdu, Sichuan 611130, P.R. China
3. Department of Cardiothoracic Surgery, The First People's Hospital of Neijiang, Sichuan 641000, P.R. China