Pathological decreases in IKs are generally mediated by congenital mutations in KCNQ1 (LQT1) or KCNE1 (LQT5), with loss-of-function mutations in KCNQ1 accounting for ~30–45% of all inherited LQT cases (Tester et al., 2005). Here, KCNQ1 is linked to long QT syndrome 5.