Figure 3.

Modeling of the Electrophysiological Consequences of Pitx2c Deficiency

(A) Propagated action potentials (top) simulated with the Courtemanche–Ramirez–Nattel model modified to reflect the more positive RMP of murine Pitx2c^+/– atria and the effect of 60% sodium current (I_Na) block at pacing cycle lengths of 500 and 1,000 ms, with 2-min pre-pacing, and corresponding time courses of the product of the 2 inactivation gates h and j of I_Na(bottom), reflecting I_Na availability. (B) Reduced sodium conductance (g_Na) increased post-repolarization refractoriness (PRR) in the reference model and the Pitx2c deficiency model. After reducing g_Na, PRR was greater in the Pitx2c deficiency model than in the reference model (grey lines). Lines denote APD₆₀(blue) and ERP (orange: with 100% gNa; grey: with 40% gNa). Abbreviations as in Figures 1 and 2.