Electrical connection between the left atrium and the pulmonary veins: a study to understand the contribution of myocardial fibers along the standard ablation circumference

Abstract Funding Acknowledgements Type of funding sources: None. Background Pulmonary vein (PV) isolation with circumferential ablation around ipsilateral PVs is the standard strategy for atrial fibrillation ablation. The electrical connection between the left atrium (LA) and the pulmonary veins (PV) is determined by the heterogeneous arrangement of myocardial fibers along the PV-LA junction. Purpose We sought to assess which regions of the standard ablation circumference are the main contributors to the venoatrial electrical connection. Methods Forty-one patients underwent a specific atrial fibrillation ablation protocol in which the anterior and posterior segments of the standard circumference were ablated first. If PV isolation was not achieved, ablation was extended superiorly or inferiorly, based on the earliest atrial activation recorded during pacing from the PV. Complete PV isolation and the length of the areas non-requiring ablation (ANRA) at the time of electrical isolation were evaluated. Results Ablation of the anterior and posterior segments of the standard circumference led to isolation of 77% left-PV pairs and 51% right-PV pairs (p=0,015). A superior extension was required in 23% left-PV pairs and in 46% right-PV pairs, while an inferior extension was required only in 10% left-PV pairs and in 11% right-PV pairs. PV isolation was achieved before completing the standard ablation circumference in 97% left-PV pairs and in 94% right-PV pairs, with an ANRA of 35.8±9.0mm in left PVs (16.1±5.2 mm superior and 19.7±5.6 mm inferior, p<0,01), and 35.5±9.5 mm in right PVs (15.2±5.7 mm superior and 20.9±5.3mm inferior, p<0,01). Conclusion The myocardial fibers along the anterior and posterior regions of the standard ablation circumference are the main contributors to the electrical connection between the LA and the PVs. Ablation of these regions results in PV isolation in the majority of patients.