1. Division of Prevention and Community Health, National Center for Cardiovascular Disease, Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
2. Department of Ultrasound Diagnosis, Tibet Second People's Hospital, Lhasa, Tibet, China.
3. Department of Internal Medicine, People's Hospital of Duilongdeqing County, Lhasa, Tibet, China.
4. Department of Cardiology, Chinese PLA General Hospital, Beijing, China.