SCN5A and familial long QT syndrome: KCNQ1 (LQT1) and KCNH2 (LQT2) encode the pore-forming subunits of voltage-gated repolarizing K+ channels conducting IKs and IKr, respectively, whereas SCN5A (LQT3) encodes the pore-forming subunit, NaV1.5, of the cardiac sodium channel conducting INa and the pathological late INa,L in LQTS [31].