Actually, the largest study to date, conducted on a cohort of SIDS victims [12] identified a disease-causing mautation in LQTS genes in about 10% of cases, and one of those mutations, the KCNQ1-I274V causes a gain of function in IKs predicting a short QT phenotype [13]. This evidence concerns the gene KCNQ1 and familial long QT syndrome.