KCNH2 and familial long QT syndrome: Mutations associated with the LQTS phenotype have been found in at least 20 genes: AKAP9, ANK2, CACNA1C, CALM1, CALM2, CALM3, CAV3, KCNE1, KCNE2, KCNH2, KCNJ2, KCNJ5, KCNQ1, KCNQ2, RYR2, SCN1B, SCN4B, SCN5A, SNTA1 and TRDN (genes and their function are described in Table 1).