1. Departments of Thoracic Surgery, Liao Cheng People’s Hospital , Liaocheng 252000 , P. R. China
2. Departments of Thoracic Surgery, Qi Lu Hospital Affiliated to Shandong University , Jinan 250021 , P. R. China
3. Departments of Thoracic Surgery, The Affiliated Taian City Centeral Hospital of Qingdao University , Taian 271000 , P. R. China
4. The Affiliated Taian City Centeral Hospital of Qingdao University , Taian 271000 , P. R. China
5. Departments of Cardiac Surgery, Liao Cheng People’s Hospital , Liaocheng 252000 , P. R. China