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.