1. Department of Cardiology, Faculty of Medicine; University of Tsukuba; Ibaraki Japan
2. Department of Cardiology; St. Luke's International Hospital; Tokyo Japan
3. Department of Cardiology; Hiratsuka Kyosai Hospital; Kanagawa Japan
4. Department of Cardiology; Yokosuka Kyosai Hospital; Kanagawa Japan
5. Department of Cardiology; Tokyo Medical and Dental University; Tokyo Japan