1. From the Cardiovascular Division, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan (Y.N., H.T., A.S., T.H., Y.S., K.A.); Cardiovascular Division, Tsukuba Medical Center Hospital, Tsukuba, Ibaraki, Japan (Y.H., Y.N.); and Cardiovascular Division, Ibaraki Prefectural Central Hospital, Kasama, Ibaraki, Japan (M.I.).