1. School of Clinical Medicine, Ningxia Medical University, Yinchuan, Ningxia 750004, P.R China
2. Department of Cardiovascular Internal Medicine, General Hospital of Ningxia Medical University, Yinchuan, Ningxia 750004, P.R China
3. School of Basic Medicine, Ningxia Medical University, Yinchuan, Ningxia 750004, P.R China