FIGURE 1.

Dynamic movement of nodal lines when alternans is V_m-driven and spatially discordant alternans is induced via steep CV restitution. (A) Spatial distribution of alternans on a 3-cm cable paced at the left end at a fixed PCL for 150 beats after which the PCL was decremented by 2 ms. The solid lines correspond to ΔAPD and dashed lines to ΔCa_i, measured after steady state has been reached. (B) Plot of nodal line position (x_node) versus beat number for the simulation in A. (C) Nodal lines in a simulated 2.25 × 2.25 cm² homogeneous tissue. The tissue is paced at the top left-hand corner using a dynamic pacing protocol where the PCL is decremented by 2 ms every 50 beats. The nodal lines are computed from ΔCa_i measured from the 49th and 50th beat. (D) Same dynamic pacing protocol applied to the bottom left-hand corner of a tissue with a fixed electrophysiological gradient in which the time constant of recovery (τ_f) of the L-type Ca_i channel increased linearly along the y axis.