1. Division of Cardiology, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
2. Division of Cardiology, Department of Internal Medicine, Severance Cardiovascular Hospital, Cardiovascular Research Institute, Yonsei University College of Medicine, Seoul, Korea.
3. Division of Cardiology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University College of Medicine, Seoul, Korea.