1. Department of Internal Medicine, Hebei Medical University, Shijiazhuang, Hebei 050011, P.R. China
2. Department of Internal Medicine, Qian'an Hospital of Traditional Chinese Medicine, Qian'an, Hebei 064400, P.R. China
3. Department of Cardiology, Tangshan Workers Hospital, Tangshan, Hebei 063000, P.R. China