SCN5A and familial long QT syndrome: It is estimated that 75%–80% of congenital LQTS are caused by pathogenic variations in either KCNQ1‐encoded Kv7.1 (LQT1), KCNH2‐encoded Kv11.1 (LQT2), or SCN5A‐encoded Nav1.5 (LQT3).