KCNH2 and torsades de pointes: This case study indicates that AP recordings in hVT combined with analysis of pro-arrhythmic score can differentiate agents that inhibit hERG with significant QTc prolongation and associate with TdP risk, such as terodiline, from agents that inhibit hERG with significant QTc prolongation but not associated with TdP risk, such as tolterodine.