Figure 1. Time course of late Na⁺ current and its effects on AP.

A: Simulation of late Na⁺ current (I_NaL) using a voltage clamp protocol similar to that of the experimental measurements obtained by Maltsev et al. [26] (shown in the right inset) in ventricular myocytes at room temperature. The left inset shows an expanded view of the current between 480 ms and 2500 ms. B: Simulated action potentials (APs) at 1-Hz pacing rate using the GPB model, the GPB model modified with control I_NaL, and I_NaL enhanced 2-fold, 5-fold and 10-fold. C: APD₉₀ sensitivity to the I_NaL amplitude. APs were simulated at 0.5-Hz (square symbols) and 1-Hz (circle symbols) pacing rate by varying I_NaL/I_NaT ratio from 0.0298% to 1.26%. The range of experimental APD at 90% repolarization (APD₉₀) for human is represented by the two discontinuous lines. D: APD₉₀ sensitivity to the I_NaL amplitude (open symbols) taken from Grandi et al. [30] who used a rabbit model.