1. Department of Thoracic and Cardiovascular Surgery, Keimyung University Dongsan Hospital, Keimyung University School of Medicine, Daegu, Korea
2. Department of Thoracic and Cardiovascular Surgery, Kyungpook National University Hospital, School of Medicine, Kyungpook National University, Daegu, Korea
3. Department of Thoracic and Cardiovascular Surgery, Konyang University Hospital, Konyang University College of Medicine, Daejeon, Korea