1. Department of Cardiology, Ibaraki Prefectural Central Hospital, Kasama, Japan
2. Department of Cardiology, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8575, Japan
3. Department of Cardiology, Nippon Medical School Hospital, Tokyo, Japan
4. Department of Pathology, Ibaraki Prefectural Central Hospital, Kasama, Japan