1. Department of Cardiology, The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150086, P.R. China
2. Department of Cardiology, The Third Affiliated Hospital, Harbin Medical University, Harbin, Heilongjiang 150086, P.R. China
3. Department of Cardiology, The Central Hospital of Handan, Handan, Hebei 056000, P.R. China
4. Department of Cardiology, The Second Hospital of Harbin, Harbin, Heilongjiang 150086, P.R. China