1. First Department of Surgery, Yokohama City University, School of Medicine, Yokohama
2. Division of Surgery, Department of Veterinary Medicine, Tokyo University of Agriculture and Technology, Tokyo
3. Division of Cardiovascular Surgery, Second Department of Surgery, Teikyo University School of Medicine, Teikyo
4. Department of Cardiovascular Surgery, Tokyo Women's Medical College, Tokyo
5. Second Department of Surgery, Kyoto Prefectural University of Medicine, Kyoto, Japan