1. Department of Surgery, Yokosuka General Hospital, Uwamachi, Kanagawa 238-8567, Japan
2. Department of Cardiovascular Internal Medicine, Yokosuka General Hospital, Uwamachi, Kanagawa 238-8567, Japan
3. Department of Cardiovascular Surgery, Yokosuka General Hospital, Uwamachi, Kanagawa 238-8567, Japan
4. Department of Surgery, Jichi Medical University, Tochigi, Japan