1. Department of Cardiovascular Surgery, National Cerebral and Cardiovascular Center , 6-1 Kishibe-Shinmachi, Suita, Osaka 564-8565 , Japan
2. Department of Pathology, National Cerebral and Cardiovascular Center , 6-1 Kishibe-Shinmachi, Suita, Osaka , Japan
3. Department of Transplant Medicine, National Cerebral and Cardiovascular Center , 6-1 Kishibe-Shinmachi, Suita, Osaka , Japan
4. Department of Pathology, National Institute of Infectious Diseases , Toyama 1-23-1, Shinjuku-ku, Tokyo , Japan