Optimal safety of conduction through the Purkinje-ventricular junction

Slow conduction through the Purkinje-ventricular junction (PVJ) is thought to result in conduction block and ultimately re-entry under certain pathological conditions. The relationships between tissue structure, conduction velocity and the safety of conduction at such junctions however, are unknown. We developed an electrophysiologically detailed 3D model of the PVJ and varied the Purkinje fibre thickness and intercellular coupling to determine these relationships. We found that both very fast and very slow AP conduction is unsafe, and there exists an optimal velocity providing the maximum safety of conduction through the PVJ. The conduction time delay across the junction is a natural consequence of the electrophysiological and morphological differences between the two tissue types. The delay allows the PVJ to accumulate and pass through sufficient charge to excite the adjacent ventricular tissue.