1. Department of Cardiovascular Surgery, Kochi Medical School Hospital , 185-1, Kohasu, Okohcho , Nankoku-shi, Kochi Prefecture 783-8505, Japan
2. Department of Cardiology, Hosogi Hospital , 35, Daizenjicho , Kochi-shi, Kochi Prefecture 780-8535, Japan
3. Department of Surgery, Kochi Medical School Hospital , 185-1, Kohasu, Okohcho , Nankoku-shi, Kochi Prefecture 783-8505, Japan