Mutual influence between dyssynchrony and transmural conduction maintains atrial fibrillation

Atrial fibrillation (AF) and other structural heart diseases cause structural remodeling in the atria. Structural remodeling leads to local heterogeneities of conduction between muscle bundles as well as between the epicardium and endocardial bundle network which enhances endo-epicardial electrical activation time differences and breakthroughs. In order to investigate the mutual influence between endo-epicardial activation time differences, breakthrough rates, and stability of AF episodes, a novel dual-layer computer model was developed. This model was composed of two layers connected by randomly distributed connection points. Two groups of simulations were selected: dual-layer and single-layer. In the dual-layer group, the amount of dyssynchrony and breakthrough rate was calculated during the course of the simulation and good correlations between dyssynchrony and breakthrough rate were observed. Stability of AF episodes was significantly higher in the dual-layer group. We conclude that transmural conduction, or `breakthrough', can be an explanation for the larger AF stability in the dual-layer group.