KCNH2 and familial long QT syndrome: Because of their typical genotype-phenotype associations, LQTS attributable to pathogenic variants in KCNQ1, KCNH2, and SCN5A have long been categorized as LQTS1-3.7,9 This nomenclature has been extended to LQTS4-17 as further genes associated with LQTS were reported.