Based on the comparison of hERG or IKr activity, cardiac action potential duration, and QT prolongation against QT effects and reports of arrhythmogenic (torsade de pointes) potential of 100 drugs, a margin of at least 30-fold between hERG IC50 and Cmax was proposed to an acceptable degree of safety from arrhythmogenesis19. Here, KCNH2 is linked to torsades de pointes.