KCNH2 and acquired long QT syndrome: ERG1 is highly susceptible to open channel block (Vorperian et al., 1996; Mohammad et al., 1997; Drolet et al., 1999; Zhang et al., 1999; Zhou et al., 1999; Sanchez-Chapula et al., 2002; Rajamani et al., 2006; Sanguinetti and Tristani-Firouzi, 2006), and off-target ERG1 block is the primary cause of acquired long QT syndrome (Sanguinetti et al., 1995).