1. Department of Cardiovascular Medicine and Nephrology, Dokkyo Medical University, Nikko Medical Center, 145-1 Moritomo, Nikko 321-2593, Tochigi, Japan
2. Department of Cardiovascular Surgery, Yamanashi University, 1110 Shimokato, Chuo-shi 409-3839, Yamanashi, Japan
3. Department of Cardiovascular Surgery, Sakakibara Heart Institute, 3-16-1 Asahi-cho, Fuchu-shi 183-0003, Tokyo, Japan