1. Division of Cardiology, Department of Internal Medicine, Seoul National University Boramae Medical Center, Seoul National University College of Medicine, Seoul, Korea.
2. Division of Cardiology, Department of Internal Medicine, Korea University Anam Hospital, Seoul, Korea.
3. Division of Cardiology, Department of Internal Medicine, Chonnam National University Hospital, Gwangju, Korea.
4. Division of Cardiology, Department of Internal Medicine, Gachon University Gil Medical Center, Incheon, Korea.
5. Division of Cardiology, Department of Internal Medicine, Hallym University Medical Center, Chuncheon, Korea.