KCNH2 and familial long QT syndrome: While there are currently 17 different LQTS types based on the gene implicated, the most common three LQTS are: LQT1 involving mutations in the KCNQ1 gene (30–35% of patients), LQT2 involves mutations in the KCNH2 gene (25–30% of patients) and LQT3 involves mutations in the SCN5a gene (10% of patients) (Cerrone et al., 2012; Priori et al., 2013).