1. Department of Cardiovascular Surgery, Kochi Medical School Hospital , 185-1, Kohasu, Okohcho, Nankoku-shi, Kochi Prefecture 783-8505 , Japan
2. Department of Cardiology and Geriatrics, Kochi Medical School Hospital , 185-1, Kohasu, Okohcho, Nankoku-shi, Kochi Prefecture 783-8505 , Japan