1 Department of Cardiovascular Surgery, Sakakibara Heart Institute, 6-22-9, Seijo, Setagaya, Tokyo, 157-0066 Japan.
2 Department of Cardiovascular Surgery, Sakakibara Heart Institute, 6-22-9, Seijo, Setagaya, Tokyo, 157-0066 Japan. Electronic address: zbn25716@nifty.com.