Time course and mechanisms of endo-epicardial electrical dissociation during atrial fibrillation in the goat.
OBJECTIVE
This study aims to determine the degree and mechanisms of endo-epicardial dissociation of electrical activity during atrial fibrillation (AF) and endo-epicardial differences in atrial electrophysiology at different stages of atrial remodelling.


RESULTS
Simultaneous high-density endo-epicardial mapping of AF was performed on left atrial free walls of goats with acute AF, after 3 weeks, and after 6 months of AF (all n = 7). Endo-epicardial activation time differences and differences in the direction of conduction vectors were calculated, endocardial and epicardial effective refractory periods (ERP) were determined, and fractionation of electrograms was quantified. Histograms of endo-epicardial activation time differences and differences in the direction of conduction vectors revealed two distinct populations, i.e. dissociated and non-dissociated activity. Dyssynchronous activity (dissociated in time) increased from 17 ± 7% during acute AF to 39 ± 17% after 3 weeks, and 68 ± 13% after 6 months of AF. Dissociation was more pronounced in thicker parts of the atrial wall (thick: 49.3 ± 21.4%, thin: 42.2 ± 19.0%, P < 0.05). At baseline, endocardial ERPs were longer when compared with epicardial ERPs (ΔERP, 21.8 ± 18 ms; P < 0.001). This difference was absent after 6 months of AF. The percentage of fractionated electrograms during rapid pacing increased from 9.4 ± 1.9% (baseline) to 18.6 ± 0.6% (6 months).


CONCLUSIONS
During AF, pronounced dissociation of electrical activity occurs between the epicardial layer and the endocardial bundle network. The increase in dissociation is due to owing to progressive uncoupling between the epicardial layer and the endocardial bundles and correlates with increasing stability and complexity of the AF substrate.
Department of Physiology, Maastricht University, Maastricht, The Netherlands. ecksteinj@uhbs.ch
Jens
J
Eckstein
Bart
B
Maesen
Dominik
D
Linz
Stef
S
Zeemering
Arne
A
van Hunnik
Sander
S
Verheule
Maurits
M
Allessie
Ulrich
U
Schotten
D000818:Animals; D001281:Atrial Fibrillation / Q000473:pathology / Q000503:physiopathology*; D004699:Endocardium / Q000503:physiopathology*; D006041:Goats; D010496:Pericardium / Q000503:physiopathology*; D012032:Refractory Period, Electrophysiological