SCN5A and long QT syndrome 3: LQT1 and LQT2 are associated with mutations in the potassium voltage-gated subfamily Q member 1 (KCNQ1) and potassium voltage-gated channel subfamily H member 2 (KCNH2) genes, respectively; whereas LQT3 is linked with mutations in the sodium voltage-gated channel alpha subunit 5 (SCN5A) gene that codes for the alpha subunit of the sodium channel Nav1.5 [18].