1. Department of Pediatrics National Defense Medical College 3‐2 Namiki Tokorozawa Saitama 359‐8513 Japan
2. Department of Pediatric Cardiology Tokyo Women's Medical University 8‐1 Kawada‐cho Shinjuku‐ku Tokyo 162‐8666 Japan
3. Department of Preventive Medicine and Public Health National Defense Medical College 3‐2 Namiki Tokorozawa Saitama 359‐8513 Japan
4. Division of Pediatric Cardiology Department of Pediatrics Okayama University 2‐5‐1 Shikata‐cho Okayama 700‐8558 Japan
5. Department of Pediatrics Toho University Medical Center Omori Hospital 6‐11‐1 Omori‐nishi Ota‐ku Tokyo Japan