Abstract 2890: The Incidence of ‘Breakthrough’ During Atrial Fibrillation Correlates With the Degree of Endo-Epicardial Dissociation in the Goat
Background: The high incidence of transmural conduction of fibrillation waves (breakthroughs) in a complex substrate for atrial fibrillation (AF) implies the presence of electrical dissociation between the subepicardial layer (Epi) and the endocardial bundle network (Endo). The degree of this Endo/Epi dissociation (EED) in remodeled atria and its role in the development of a substrate for AF has not been studied yet.
Methods: Left atrial high resolution simultaneous endo-epicardial activation maps were obtained in three groups of goats (acute, 3 weeks, and 6months AF, each n=7). Single fibrillation waves were identified as areas surrounded by lines of block and categorized according to their origin in peripheral waves (from outside the mapping area) or ‘breakthrough’ (originating inside the mapping area). Dissociation between endo- and epicardial waves was quantified according to their differences in activation time and direction of propagation.
Results: The number of waves increased with AF duration (p<0.001). At the same time, the size of waves decreased (p<0.001) while the percentage of endo-epicardially dissociated waves and the incidence of ‘breakthrough’ increased (p<0.001). There was a positive correlation between the degree of EED and the incidence of ‘breakthroughs’ for all individual animals (R=0.71).
Conclusion: During AF, pronounced endo-epicardial electrical dissociation occurs. Endo-epicardial dissociation and the incidence of ‘breakthrough’ increase over time, contributing to the progressive complexity of the substrate of AF. Enhanced endo-epicardial dissociation might well explain the high incidence of transmural conduction (breakthroughs) in a complex substrate for AF.