FIGURE 3.

Induction of dispersion of refractoriness and conduction block in homogeneous 1D cable of the LR1 model. The S1 was applied at one end whereas S2 and S3 were applied at the other end. (A) APD gradient induced by S2 for normal Na⁺ recovery with ΔT_S1S2 = 280 ms (solid line) and for fivefold-slowed Na⁺ channel recovery with ΔT_S1S2 = 287 ms (dashed line). (B) Vulnerable window (shaded area) of conduction block of the S3 beat for different S1S2 coupling intervals with normal Na⁺ channel recovery. “S2 failure” indicates an S1S2 interval is too short for S2 to stimulate the S2 waves. (C) Vulnerable window size w versus the induced maximum APD difference Δa for normal Na⁺ channel recovery (▪) and slowed Na⁺ channel recovery (□). Data were obtained from different S1S2 coupling intervals.