(A,B) Endocardial and Purkinje AP used as an AP clamp (5th beat of the simulation shown). (C) IKr produced by the endocardial AP. (D) IKr produced by the Purkinje AP. Shown are data manually extracted from Lu et al. (2001), as well as simulations using ORd and ToR-ORd (L-V, coding for Lu-Vandenberg hERG model). A normalisation was performed in (C), (D) to facilitate the relative loss of IKr using the low-plateau AP shape. In (C), the three traces were normalised to 0–1 range via division by maxima of the traces: maxData, maxORd, maxLV. Subsequently, in (D), the data trace was divided by maxData, ORd simulation by maxORd, and the ToR-ORd model simulation by maxLV. Thus, both traces produced by a given model (or measured experimentally) are divided by the same number, allowing the assessment of relative reduction of IKr at the low-plateau AP.