This review provides a brief background on the initial phenotypic identification of congenital LQTS and discusses the different mechanisms by which KCNQ1 (Kv7.1) or KCNH2 (Kv11.1) mutations can impact K+ currents and channel function to cause LQT1 and LQT2, respectively. This evidence concerns the gene KCNQ1 and familial long QT syndrome.