1. Department of Cardiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
2. Department of Cardiology, Kyung Hee Medical Center, University of Kyung Hee College of Medicine, Seoul, Korea.
3. Department of Cardiology, Dong-A University Hospital, University of Dong-A College of Medicine, Busan, Korea.
4. Department of Thoracic and Cardiovascular Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.