KCNH2 and familial long QT syndrome: Moreover, 17 genes have been identified as responsible of LQTS, with 3 major genes such as KCNQ1 (LQT1), KCNH2 (LQT2), and SCN5A (LQT3) responsible for 75% of cases and 14 minor genes such as AKAP9, CACNA1C, CALM1, CALM2, CALM3, CAV3, KCNE1, KCNE2, KCNJ2, KCNJ5, SCN4B, SCN5A, SNTA1, and TRDN responsible for less than 5% of cases (Figure 3) [41].