1. Department of Cardiology, Japan Red Cross Yokohama City Bay Hospital, 3-12-1, Shinyamashita, Naka-ward, Yokohama City, Kanagawa 231-8682, Japan
2. Department of Cardiovascular Medicine, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ward, Tokyo 113-8510, Japan