Contribution of the Purkinje network to wave propagation in the canine ventricle: insights from a combined electrophysiological-anatomical model

The heart includes a specialized conduction system that ensures the necessary activation sequence and timing of the ventricles to produce an effective contraction. The role of this system, called the Purkinje network, during ventricular tachyarrhythmias remains unclear. To understand how the Purkinje network interacts with ventricular muscle, we develop the first combined electrophysiology-structural model of the canine Purkinje network based on microelectrode recordings and a digitized reconstruction of the Purkinje system. For the Purkinje electrophysiology model, we construct a new model of canine Purkinje electrophysiology based on action potentials recorded from canine tissue and designed to reproduce the important phenomenon of alternans. In addition, we use digital photographs of canine ventricular endocardium stained with Lugol's solution to develop a structural model of the Purkinje network. We combine these electrophysiological and anatomical models of the Purkinje system with a model of canine ventricular electrophysiology to study how the Purkinje network can interact with the ventricular muscle during arrhythmias. Using our combined model, we find that two different results can occur: The long-range connections provided by the Purkinje network can depolarize the tissue more quickly, thereby promoting arrhythmia termination, but if termination does not occur, the Purkinje system can increase the dispersion of refractoriness in the tissue, thereby sustaining the arrhythmia. The different behaviors result from the two competing effects contributed by the Purkinje network: effective reduction in tissue size and increased spatial heterogeneity.