1 Department of Thoracic and Cardiovascular Surgery, St. Paul's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
2 Department of Thoracic and Cardiovascular Surgery, Bucheon St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Bucheon, Korea.
3 Department of Thoracic and Cardiovascular Surgery, Incheon St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Incheon, Korea.