KCNH2 and familial long QT syndrome: Inherited LQTS has been linked to mutations in several cardiac ion channels with KCNQ1 (LQTS1), KCNH2 (LQTS2), and SCN5A (LQTS3) being the most common LQTS genes, accounting for ∼90% of all genotype-positive cases (Schwartz et al., 2012).