Transmural Conduction Is the Predominant Mechanism of Breakthrough During Atrial Fibrillation Evidence From Simultaneous Endo-Epicardial High-Density Activation Mapping

Background-Endo-epicardial dissociation (EED) of electric activations resulting in transmural conduction of fibrillation waves (breakthroughs) has been postulated to contribute to the complexity of the substrate of atrial fibrillation (AF). The aim of this study was to elucidate the correlation between EED and incidence of breakthrough and to test the plausibility of transmural conduction versus ectopic focal discharges as sources of breakthrough. Methods and Results-We analyzed high-resolution simultaneous endo-epicardial in vivo mapping data recorded in left atrial free walls of goats with acute AF, 3 weeks and 6 months of AF (all n=7). Waves were analyzed for number, size, and width and categorized according to their origin outside (peripheral wave) or within the mapping area (breakthrough). Breakthrough incidence was lowest (2.1 +/- 1.0%) in acute AF, higher (11.4 +/- 6.1%) after 3 weeks (P