KCNH2 and familial long QT syndrome: The most common types of LQTS are LQTS1 (30–35% of patients; Ackerman et al., 2011), LQTS2 (25–40%), and LQTS3 (5–10%), due to defects in KCNQ1 (KV7.1 channel), KCNH2 (KV11.1), and SCN5A (Nav1.5) genes, respectively.