Jing Liu1,2, Changsheng Ma3. 1. Department of Epidemiology, Beijing Anzhen Hospital, Capital Medical University, National Clinical Research Center for Cardiovascular Diseases, Beijing, China. 2. Beijing Institute of Heart, Lung and Blood Vessel Diseases, Beijing, China. 3. Department of Cardiology, Beijing Anzhen Hospital, Capital Medical University, National Clinical Research Center for Cardiovascular Diseases, Beijing, China. chshma@vip.sina.com.