However, only 20–30% of patients with SQTS have an identifiable mutation.5,6 To date, only four genes encoding potassium channels (KCNQ1, KCNH2, and KCNJ2) and the chloride-bicarbonate exchanger AE3 (SLC4A3) have been clearly associated with pathogenic SQTS.7–9 However, we still lack detailed information about the factors responsible for the relative malignancy and specific arrhythmogenic mechanisms of each of the known mutations. This evidence concerns the gene KCNJ2 and Familial short QT syndrome.