Effect of resistive discontinuities on waveshape and velocity in a single cardiac fibre

A computer model of a one-dimensional cardiac fibre of resistively coupled cells is used to investigate the influence of the junction resistance on the nature of conduction. The results of the simulations are presented and indicate that the effect of the junction on both intracellular and extracellular waveshape and on the velocity of propagation depends on the size and frequency of the coupling resistance and the kinetics of the active membrane. Significant changes in these factors are not observed without the generation of prepotentials in the action potential upstroke. The absence of this ‘signature’ in microelectrode recordings of activity in ventricular muscle suggests that under normal conditions cardiac tissue behaves as a functional syncytium.