Alternans and period-doubling bifurcations in atrioventricular nodal conduction.

A theoretical model, formulated as a finite difference equation is proposed for rate-dependent conduction properties of the atrioventricular (AV) node. The AV nodal conduction time, which is defined as the time interval from the atrial activation to the activation of the bundle of His, depends on the history of activation of the node. The theoretical model, which incorporates physiological concepts of recovery, facilitation and fatigue, accurately predicts a variety of experimentally observed complex rhythms of nodal conduction. In particular, alternans rhythms, in which there is an alternation in conduction time from beat to beat, are associated with period-doubling bifurcations in the theoretical model.