SCN5A and familial long QT syndrome: Nav1.5 (the pore-forming, ion-conducting α-subunit of the cardiac sodium channel) is encoded by SCN5A, and variants in this gene have been implicated in a wide range of cardiac diseases such as Brugada syndrome, LQTS, AF, SND, dilated cardiomyopathy, and others (Wilde and Amin, 2018).