1. International Medical Center, Geriatric Department, National Clinical Research Center of Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan 410008, P.R. China
2. Department of Cardiology, Changsha Central Hospital, Changsha, Hunan 410000, P.R. China
3. Department of Cardiology, The Second Xiangya Hospital of Central South University, Changsha, Hunan 410011, P.R. China
4. Department of Cardiology, Xiangya Hospital of Central South University, Changsha, Hunan 410008, P.R. China