1. Department of Cardiovascular Medicine, Omihachiman Community Medical Center, 1379 Tsuchidacho, Omihachiman, Shiga 523-0082, Japan
2. Department of Cardiovascular Surgery, University Hospital, Kyoto Prefectural University of Medicine, 465 Kaji-cho, Kamigyo-ku, Kyoto-shi, Kyoto 602-8566, Japan