1. Cardiovascular Center, Department of Internal Medicine, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Korea.
2. Cardiovascular Center, Department of Internal Medicine, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Korea.
3. Division of Cardiology, Department of Internal Medicine, Kangwon National University College of Medicine, Kangwon National University School of Medicine, Chuncheon, Korea.
4. Department of Cardiology, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea.