1. Department of Thoracic and Cardiovascular Surgery, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Korea.
2. Department of Thoracic and Cardiovascular Surgery, Yongin Severance Hospital, Yonsei University College of Medicine, Yongin, Korea.
3. Department of Thoracic and Cardiovascular Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.