ELECTRICAL COUPLING AND IMPULSE PROPAGATION IN ANATOMICALLY MODELED VENTRICULAR TISSUE

Computer simulations were used to study the role of resistive coupling s on flat-wave action potential propagation through a thin sheet of ve ntricular tissue. Unlike simulations using continuous or periodic stru ctures, this unique electrical model includes random size cells with r andom spaced longitudinal and lateral connections to simulate the phys iologic structure of the tissue. The resolution of the electrical mode l is ten microns, thus providing a simulated view at the subcellular l evel. Flat-wave longitudinal propagation was evaluated with an electri cal circuit of over 140,000 circuit elements, modeling a 0.25 mm by 5. 0 mm sheet of tissue. An electrical circuit of over 84,000 circuit ele ments, modeling a 0.5 mm by 1.5 mm sheet was used to study flat-wave t ransverse propagation. Under normal cellular coupling conditions, at t he macrostructure level, electrical conduction through the simulated s heets appeared continuous and directional differences in conduction ve locity, action potential amplitude and V-max were observed. However, a t the subcellular level (10 mu m) unequal action potential delays were measured at the longitudinal and lateral gap junctions and irregular wave-shapes were observed in the propagating signal. Furthermore, when the modeled tissue was homogeneously uncoupled at the gap junctions c onduction velocities decreased as the action potential delay between m odeled cells increased. The variability in the measured action potenti al was most significant in areas with fewer lateral gap junctions, i.e ., lateral gap junctions between fibers were separated by a distance o f 100 mu m or more.