Fig. 9.

Effect of heterogeneities in myofibroblast (Myofib) density on propagation when myofibroblasts are located on top of myocytes and exert a purely paracrine effect on myocytes by reducing gap junctions and cell-to-cell conductance. A: propagation of a premature impulse (S1S2 = 196 ms) in a preparation with a myofibroblast density of ∼50%. The propagating impulse does not block. B: block of a premature impulse (S1S2 = 196 ms) at the boundary between an area with myofibroblasts (density 50%) and an area without myofibroblasts.