1. From the Hypertrophic Cardiomyopathy Center, Division of Cardiology, Tufts-New England Medical Center, Boston, Mass (M.S.M., J.E.U., M.S.L., J.T.K., N.G.P.); Regional Referral Center for Myocardial Diseases, Azienda Ospedaliera Careggi, Florence, Italy (I.O., S.N., F.C.); and Hypertrophic Cardiomyopathy Center, Minneapolis Heart Institute Foundation, Minneapolis, Minn (A.G.Z., B.J.M.).