Figure 5. Simulated action potentials and reentry in WT and TG hearts.

A, simulated mouse ventricular action potential and main currents involved in repolarization. I_K1 is multiplied by a factor of 10 for illustration purposes. B, action potentials and respective underlying I_K1 for WT (black) and TG (red) hearts. The conductance of I_K1 in TG is 12 times greater than in the WT hearts. C, spatial distribution of transmembrane voltage (top) and inactivation gating variables (‘hj’ gates, bottom) of the I_Na during stable reentry in a 2 cm × 2 cm cardiac cell sheet. The diastolic potential is more hyperpolarized over a wider area in the TG heart sheet (∼−94 mV), compared to the WT case (∼−90 mV). The ‘hj’ gate map shows that the maximum availability of Na⁺ channels in TG (0.808) exceeds that of the WT heart (0.684), and occupies a larger area during the excitable gap.