1. Department of Thoracic and Cardiovascular Surgery, Kangnam Sacred Heart Hospital, Hallym University Medical Center, Hallym University College of Medicine, Seoul, Korea.
2. Department of Thoracic and Cardiovascular Surgery, Bucheon Sejong Hospital, Bucheon, Korea.
3. Division of Cardiology, Department of Internal Medicine, Bucheon Sejong Hospital, Bucheon, Korea.
4. Department of Thoracic and Cardiovascular Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.