Figure 1. Mechanisms of scar re-entry.

Heterogeneously distributed scar forms electrical conduction barriers but also facilitate the formation of critical isthmuses of viable myocytes that support re-entrant circuits (Panels A and B, collagen bundles shown in blue on Masson’s trichrome staining). Panel C: Wavefronts can enter the proximal end of the isthmus (entrance), exiting from the distal end (exit) and then propagating throughout the ventricle to form the QRS complex. The wavefront can re-enter the isthmus from channels within the infarct (inner loop) or via an outer loop at the border of the infarct zone with the normal myocardium. Reprinted with permission from: Danciu M.²¹ and Ajijola A. et al.²²