1. Department of Geriatrics, Gansu Institute of Traditional Chinese Medicine, Gansu Provincial Hospital of Traditional Chinese Medicine, Lanzhou, Gansu 730050, P.R. China
2. Department of Nephropathy, People's Hospital of Wuwei, Wuwei, Gansu 733000, P.R. China
3. ECG Room, Xi'an no. 3 Hospital, Xi'an, Shaanxi 710008, P.R. China
4. Department of Geriatrics, Baoji City People's Hospital, Baoji, Shaanxi 721000, P.R. China