In most LQTS cases, causative mutations have been identified in the KCNQ1 or KCNH2 gene, which encode the pore-forming subunits of the two physiologically important potassium channels required for the slow and rapid delayed rectifier currents, IKs and IKr, respectively [7,8]. The gene discussed is KCNQ1; the disease is familial long QT syndrome.