FAILURE OF IMPULSE PROPAGATION IN A MATHEMATICALLY SIMULATED ISCHEMICBORDER ZONE - INFLUENCE OF DIRECTION OF PROPAGATION AND CELL-TO-CELL ELECTRICAL COUPLING

Introduction: It is suggested that heterogeneous extracellular potassi um concentration, cell-to-cell coupling, and geometric nonuniformities of the ischemic border zone contribute to the incidence of unidirecti onal block and subsequent development of lethal ventricular arrhythmia s. Method and Results: A discrete electrical network was used to model a single cardiac fiber with a [K+](e) gradient characteristic of an i schemic border zone, Directional differences in propagation were evalu ated by creating discrete regions with increased gap junctional resist ance within the [K+](e) gradient, Furthermore, the effect of homogenei ty/heterogeneity of cell length on impulse propagation through the [K](e) gradient in the presence of increased gap junctional resistance w as evaluated, The results indicate that failure of impulse propagation occurs at the junction between partially uncoupled and normally coupl ed cells, Furthermore, propagation failure was more likely to occur as the impulse propagated from a region of high [K+](e) to low [K+](e). Heterogeneity in cell length contributes to the variability in the occ urrence of unidirectional and bidirectional block. Conclusions: The on set of cellular uncoupling in an ischemic border zone may interact wit h the inherent [K+](e) gradient leading to unidirectional conduction b lock, This mechanism may be important for the generation of reentrant arrhythmias at the ischemic border zone.