1. Department of Preventive Medicine, School of Medicine, The Catholic University of Korea, Seoul, Korea.
2. The Korean Cardiac Research Foundation, Seoul, Korea.
3. Department of Internal Medicine, Chungbuk National University Hospital, Chungbuk National University, College of Medicine, Cheongju, Korea.
4. Department of Internal Medicine, St. Vincent’s Hospital, The Catholic University of Korea, Suwon, Korea.