Figure 1

(Color online) Space-time voltage plots of complete block (a) and unidirectional block (b) on the second premature wave S3. Horizontal axis is cell number and vertical is time in ms. The 1D fiber is $10\mathrm{cm}$ long (400 cells $0.025\mathrm{cm}$ apart). Symmetric block in (a) was induced by launching waves in the midspan of the fiber (cell 200) so that the propagation is undisturbed by the far boundaries while unidirectional block in (b) was induced by stimulating at cell 340 so that the right-hand boundary at cell 400 ($1.5\mathrm{cm}$ to the right of the stimulus) was in the vicinity. The ionic model was the 3V-SIM and the range of normalized voltage values, (0,1.3), was rescaled to $(-100,100)$. The interstimulus intervals were determined from the effective refractory period (ERP) of the previous wave: (${\mathrm{ERP}}_{\mathrm{S}1}+1\mathrm{ms}$, ${\mathrm{ERP}}_{\mathrm{S}2}+6\mathrm{ms}$) for (S2, S3).Reuse & Permissions

Figure 2

(Color online) (a) APD differences between cells near the wall and in the bulk extracted from Fig. 1b for S1 and S2. (b) Space-time plot of deposited diffusion current during S2. The plot shows the contribution to ${\partial }_{t}V$ from the first term on the right-hand side of Eq. (1), ${\nabla }^{2}V$. The results were obtained from the simulation shown in Fig. 1b and the values were rescaled to ($-100$, 100).Reuse & Permissions

Figure 3

(Color online) Influence of a boundary on diffusive currents. Schematics of the wave-back in a space-time voltage plot when a wall is present (right-hand column) and absent (left-hand column). The wave back moves towards the right in the top panels and towards the left in the bottom. Blue arrows represent diffusion currents (proportional to $-\nabla V$). The wall reduces the amount of current that is drawn into tissue near a wall when the wave back moves towards the wall (b), and reduces the current lost from tissue near a wall when the wave back moves away from the wall (d).Reuse & Permissions

Figure 4

Comparison of the APD-DI relation between cells near the wall and cells to the left of the stimulus site. (a) Procedure to construct the spatial restitution plot shown in (b). (b) Relation between APD and DI for S2 obtained from Fig. 1b. APD for cells near the wall (thin line, left and horizontal axes) are plotted together with the corresponding APD for cells on the other side of the site of stimulation that share the same DI (thick line, left-hand axis, unspecified cell number). The common DI for each pair of APDs is shown as a bar (right-hand axis).Reuse & Permissions

Figure 5

(Color online) Simulation similar to that in Fig. 1a except that four premature stimuli were delivered. The sequence was short-long-short-short: (${\mathrm{ERP}}_{\mathrm{S}1}+1$, ${\mathrm{ERP}}_{\mathrm{S}2}+31$, ${\mathrm{ERP}}_{\mathrm{S}3}+1$, ${\mathrm{ERP}}_{\mathrm{S}4}+6$) in ms for (S2, S3, S4, S5).Reuse & Permissions

Figure 6

(a) Same analysis as that shown in Fig. 2a for premature waves up to S4 extracted from Fig. 5b. (b) Same analysis as that in Fig. 4b for S3 obtained from Fig. 5b.Reuse & Permissions

Figure 7

(Color online) (a)–(c) Anisotropic block during S5 in two dimensions. The domain was $400\times 400$ cells (cell $\text{spacing}=0.025\mathrm{cm}$) and waves were launched at cells $(x,y)=(340,200)$ in such a way that the boundary at $x=400$ is near the stimulus site. The variable $t$ denotes time lapsed since stimulation of S5 and the voltage range ($-100\mathrm{mV}$, $20\mathrm{mV}$) was rescaled to ($-100$, 100). Only the portion of the domain near the right-hand wall is being shown. The sequence was short-long-short-short: (${\mathrm{ERP}}_{\mathrm{S}1}+1$, ${\mathrm{ERP}}_{\mathrm{S}2}+31$, ${\mathrm{ERP}}_{\mathrm{S}3}+1$, ${\mathrm{ERP}}_{\mathrm{S}4}+9$) in ms for (S2, S3, S4, S5). (d) Time space plot for S4 and S5 recorded from the 2D simulation through the line $y=200$.Reuse & Permissions