KCNH2 and torsades de pointes: Certain marketed drugs, such as verapamil and ranolazine, block hERG but are not linked with TdP.11,12 There are therefore concerns that hERG block lacks specificity (gives false positives for TdP risk), preventing the development of potentially useful drugs.13 As such, elucidation of other factors that mediate TdP risk is needed.