A computer model of endo-epicardial electrical dissociation and transmural conduction during atrial fibrillation

Structural alterations during atrial fibrillation (AF) not only lead to electrical dissociation within the epicardial layer, but also between the epicardial layer and the endocardial bundle network. The aim of the study was to investigate the role of transmural conduction in the stability of AF episodes using a dual-layer computer model.

A proof-of-principle dual-layer model was developed in which connections between the layers can be introduced or removed at any time during the simulation. Using an S1-S2 protocol, a spiral wave was initiated in one of the layers, which degenerated into a complex AF pattern after connection with the other layer at six randomly chosen sites. After 6 s, connections were either retained (dual-layer simulations) or removed (single-layer simulations). Dual-layer simulations were more complex, as indicated by the higher number of waves and phase singularities. Tracking waves through both layers revealed that the number of waves in dual-layer simulations was significantly higher than in the single-layer simulations, reflecting more opportunities for reentry and a concomitant increase in AF stability. In the dual-layer model, only 12% of the AF episodes died out within 6 s, while 59% died out in the single-layer model.

Atrial fibrillation patterns are more complex and AF episodes are more stable in a dual-layer model. This study indicates an important role for endo-epicardial conduction for the stabilization of AF.