1. School of Medicine, Nankai University, Tianjin 300071, P.R. China
2. Department of Cardiology, The First College of Clinical Medical Science, China Three Gorges University, Yichang, Hubei 443000, P.R. China
3. Department of Cardiology, Beijing Tsinghua Changgeng Hospital, School of Clinical Medicine, Tsinghua University, Beijing 100084, P.R. China