1. Department of Cardiovascular Surgery, University of Tsukuba, Tsukuba, Japan
2. Department of Cardiovascular Surgery, Tokyo Metropolitan Children’s Medical Center, Tokyo, Japan
3. Department of Cardiovascular Surgery, Ibaraki Children’s Hospital, Mito, Japan
4. Department of Cardiovascular Surgery, Suetsugu Clinic, Tsukuba, Japan
5. Department of Biostatistics, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan