KCNH2 and familial long QT syndrome: Inherited long QT syndrome (LQTS) is a genetic heart disease caused predominantly by pathogenic variants in KCNQ1-encoded Kv7.1 channels (type 1 LQTS, LQT1), KCNH2-encoded Kv11.1 channels (type 2 LQTS, LQT2), and SCN5A-encoded Nav1.5 channels (type 3 LQTS).3,4,5 It is characterized by prolonged ventricular repolarization and an increased risk for torsadogenic syncope/seizures, sudden cardiac arrest, and sudden cardiac death.4