1. Division of Cardiology, Department of Internal Medicine, Kangwon National University School of Medicine, Kangwon National University Hospital, Chuncheon, Korea.
2. Department of Cardiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.
3. Division of Biostatistics, Center for Medical Research and Information, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.
4. Department of Cardiology, Chungnam National University Hospital, Daejeon, Korea.