Asymptomatic or borderline LQTS mutation carriers are highly represented in the LQTS population [36 and 19%, respectively, for LQT1 and LQT2 (Schwartz et al, 2012)], and they are particularly susceptible to hERG blockers (Fitzgerald & Ackerman, 2005). This evidence concerns the gene KCNQ1 and familial long QT syndrome.