1 Teine Keijinkai Hospital, Department of Cardiovascular Surgery, 1-40 Maeda 1 Jo 12 Chome, Teine-ku, Sapporo, Japan 006-8555. Electronic address: kurimoto-spr@umin.ac.jp.
2 Teine Keijinkai Hospital, Department of Cardiovascular Surgery, 1-40 Maeda 1 Jo 12 Chome, Teine-ku, Sapporo, Japan 006-8555.