Among these mutations, LQT1 (KCNQ1) and LQT2 (KCNH2) are the most common types of LQTS, accounting for more than 70  % of LQTS, whilst LQT3 (SCN5A) is responsible for less than 10 % of the cases. This evidence concerns the gene KCNQ1 and familial long QT syndrome.