1. Department of Cardiology, Zaozhuang Municipal Hospital, Zaozhuang, Shandong 277100, P.R. China
2. Department of Cardiology, Zaozhuang Hospital of Zaozhuang Mining Group, Zaozhuang, Shandong 277100, P.R. China
3. Nursing Department, Zaozhuang Hospital of Traditional Chinese Medicine, Zaozhuang, Shandong 277100, P.R. China