1. Department of Nursing, Xian'yang Vocational and Technical College, Fengxi New Town United Avenue, Xi'an, Shaanxi 712000, P.R. China
2. Department of Cardiology, Shaanxi Provincial People's Hospital and The Third Affiliated Hospital, Xi'an Jiaotong University, Xi'an, Shaanxi 710068, P.R. China
3. Department of Cardiology, Affiliated Hospital of Shaanxi Traditional Chinese Medicine University, Xianyang, Shaanxi 712000, P.R. China