1. Division of Cardiology, Department of Internal Medicine, Gachon University Gil Medical Center, Incheon, Korea.
2. Division of Cardiology, Department of Internal Medicine, Korea University Guro Hospital, Seoul, Korea.
3. Division of Cardiology, Department of Internal Medicine, Chungbuk National University Hospital, Cheongju, Korea.
4. Division of Cardiology, Department of Internal Medicine, Korea University Anam Hospital, Seoul, Korea.
5. Division of Cardiology, Department of Internal Medicine, Sejong General Hospital, Bucheon, Korea.