Loss‐of‐function hERG mutations underpin the LQT2 form of congenital long QT syndrome (LQTS), whilst gain‐of‐function mutations underlie the SQT1 form of congenital short QT syndrome (SQTS); both conditions predispose to malignant arrhythmias and sudden death (Hancox, Whittaker, Du, Stuart, & Zhang, 2018; Sanguinetti & Tristani‐Firouzi, 2006). Here, KCNH2 is linked to familial long QT syndrome.