HCN4 and familial long QT syndrome: These 49 rare variants were localized in 14 genes encoding ion channels or associated proteins: ABCC9 (two in BrS), AKAP9 (four in LQTS), ANK2 (one in LQTS), CACNB2 (two in BrS), HCN4 (three in BrS), KCND3 (one in BrS), KCNH2 (nine in LQTS), KCNJ2 (one in LQTS), KCNQ1 (seven in LQTS), RyR2 (seven in CPVT), SCN10A (one in BrS), SCN5A (seven in BrS and one in LQTS), SNTA1 (two in LQTS), and TRPM4 (one in BrS) (Fig. 1).