1. Department of Cardiothoracic Surgery, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, P.R. China
2. Department of Cardiothoracic Surgery, Peace Hospital of Changzhi Medical College, Changzhi, Shanxi 046000, P.R. China
3. Department of Anesthesiology, Peace Hospital of Changzhi Medical College, Changzhi, Shanxi 046000, P.R. China