1. From the Hypertrophic Cardiomyopathy Center, Minneapolis Heart Institute Foundation, Minneapolis, MN (B.J.M., S.A.C., T.S.H., R.F.G., J.R.L.); Hypertrophic Cardiomyopathy Center, Tufts Medical Center, Boston, MA (E.J.R., J.E.U., M.S.M.); PERFUSE Core Laboratory and Data Coordinating Center, Harvard Medical School, Boston, MA (R.H.M.C., E.A.); and Department of Medicine, Cardiovascular Division, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA (W.J.M.).