1. From the Unit for Inherited Heart Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark (M.K.J., H.B.); Karolinska University Hospital, Stockholm, Sweden (L.J., M.J.E.); Oslo University Hospital, Rikshospitalet, Oslo, Norway (V.A., S.A.); Heart and Diabetes Center NRW, Bad Oeynhausen, Germany (F.v.B., L.F.); and Gentofte Hospital, Hellerup, Denmark (P.R.H., T.F.H.).