Loss of function mutations in hERG1 are a common cause of LQTS (Curran et al., 1995), a disorder of ventricular repolarization that is associated with potentially life threatening arrhythmia and ventricular fibrillation (Jervell and Lange-Nielsen, 1957; Schwartz et al., 1991). Here, KCNH2 is linked to familial long QT syndrome.