1. International Medical Center, Geriatric Department, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital of Central South University, Changsha, Hunan 410008, P.R. China
2. Department of Cardiovascular Medicine, Changsha Central Hospital, Changsha, Hunan 410001, P.R. China
3. Department of Cardiovascular Medicine, Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, P.R. China
4. Department of Cardiovascular Medicine, Xiangya Hospital of Central South University, Changsha, Hunan 410008, P.R. China