1. Department of Cardiology, Liaocheng People's Hospital of Shandong University, Liaocheng, Shandong 252000, P.R. China
2. Shandong Institute for Endemic Disease Control, Jinan, Shandong 250014, P.R. China
3. Department of Cardiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, P.R. China