1. Division of Cardiovascular Surgery, Tohoku University Hospital
2. Department of Thoracic and Cardiovascular Surgery, Hirosaki University Hospital
3. Department of Cardiovascular Surgery, Aomori Prefectural Central Hospital
4. Department of Cardiovascular Surgery, Akita University Hospital
5. Department of Cardiovascular Surgery, Iwate Medical University Hospital
6. Department of Cardiovascular Surgery, Iwate Prefectural Central Hospital
7. Second Department of Surgery, Yamagata University Hospital
8. Department of Cardiovascular Surgery, Yamagata Prefectural Central Hospital
9. Department of Cardiovascular Surgery, Nihonkai General Hospital
10. Department of Cardiovascular Surgery, Tohoku Medical and Pharmaceutical University Hospital
11. Department of Cardiovascular Surgery, Sendai Kosei Hospital
12. Department of Cardiovascular Surgery, Fukushima Medical University Hospital
13. Department of Cardiovascular Surgery, Southern Tohoku General Hospital