Risk factors are represented by the location and type of mutation (with higher risk in case of transmembrane missense mutations) and the LQTS genotype (10- and 8-fold increase in the risk of life-threatening events in case of LQTS1 and LQTS3 genotypes, respectively, compared with the LQT2 genotype in normal-QTc individuals). This evidence concerns the gene KCNH2 and familial long QT syndrome.