Abstract 1363: Endo-epicardial Dispersion of Refractoriness in the Goat model of AF
Background: Conduction of fibrillation waves during atrial fibrillation (AF) is a three-dimensional process. Endo-epicardial dispersion in refractoriness might increase electrical dissociation between the subepicardial layer and the endocardial bundle network facilitating unidirectional block and promoting AF.
Methods and Results: We developed a clamp-like mapping tool with 156 epicardial and 90 endocardial electrodes (spacing 1.6mm) allowing simultaneous epi-endocardial high density mapping and pacing of the atria. This tool enabled us to determine effective atrial refractory periods (AERP) at exactly opposing endo- and epicardial sites. 8 control goats and 8 goats with 3 weeks of artificially maintained AF were included. In all animals multiple sites of the left and right atrial free walls were mapped during sinus rhythm (SR), atrial pacing at 400 and 250ms cycle length and AF. During sinus rhythm and atrial pacing, there was uniform and rapid conduction in the epi- and the endocardium with similar conduction velocities during SR in controls (epi: 104±9cm/s endo: 93±14cm/s, n.s.) and AF group (epi 97±16cm/s endo 86±15cm/s, n.s.). In both groups, AERPs were significantly longer endocardially compared to epicardially (Δ epi-endo AERP Control 22±10ms, AF group 17±8ms, p=0.001). This was true for all sites and both cycle lengths tested.
Conclusion: Effective atrial refractory periods differ significantly between endo- and epicardium at exactly opposing sites. This holds true for control animals as well as animals in persisting AF. Endo-epicardial dispersion of refractoriness might promote AF by enhancing electrical dissociation between the subepicardial layer and the endocardial bundle network.