1. Key Laboratory of Education of the Ministry for Myocardial Ischemia, Division of Cardiovascular Surgery, The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150086, P.R. China
2. Division of Epidemiology and Biostatistics, School of Public Health, Harbin Medical University, Harbin, Heilongjiang 150000, P.R. China
3. Division of Thoracic Surgery, Tang Du Hospital, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
4. Department of General Surgery, The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150000, P.R. China