From the Cardiovascular Division, Institute of Clinical Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki (Y.N., H.T., A.S., K.Y., Y.S., K.A.); the Cardiovascular Division, Tsukuba Medical Center Hospital, Tsukuba, Ibaraki (Y.H., Y.N.); and the Cardiovascular Division, Ibaraki Prefectural Central Hospital, Kasama, Ibaraki, Japan (M.H.).(2012-06時点)