1 Department of Thoracic, Cardiovascular and General Surgery, Kanazawa University, 13-1 Takaramachi, Kanazawa 920-8641, Japan. Electronic address: knj.iino@gmail.com.
2 Department of Healthcare Quality Assessment, University of Tokyo, Tokyo, Japan.
3 Department of Cardiovascular Surgery, Toho University, Sakura Medical Center, Sakura, Japan.
4 Department of Cardiovascular Surgery, NewHeart Watanabe Institute, Tokyo, Japan.
5 Department of Thoracic, Cardiovascular and General Surgery, Kanazawa University, Kanazawa, Japan.
6 Japan Cardiovascular Surgery Database Organization, Tokyo, Japan.