1. Department of Cardiovascular Surgery, National Cerebral and Cardiovascular Center, 6-7 Kishibeshinmachi, Suita, Osaka 564-8565, Japan
2. Department of Cardiovascular Surgery, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan
3. Department of Pediatric Cardiovascular Surgery, National Cerebraland Cardiovascular Center, Osaka, Japan