KCNH2 and torsades de pointes: In addition to being of interest in drug-induced TdP, the IKr potassium current is also involved in LQT2, and is also linked to EADs.9 Loss-of-function mutations in hERG cause a reduction in the IKr current of up to 97%,32 which causes QT prolongation, and usually increases risk of TdP.