The impact of escape mapping for roof line completion during BOX isolation for atrial fibrillation

Abstract Background and Aim The creation of complete roof line (RL) is often challenging due to the presence of epicardial myocardial bundle or fat interposition. The disconnecting the septopulmonary bundle from the Buchmann bundle arrays requires for RL completion. Therefore, the conduction time to the left atrial appendage (LAA) and the high right atrium (HRA) potentials under left superior pulmonary vein pacing (LSPVp), so-called •escape mapping•, should be significantly prolonged after the creation of the transmural RL. This study investigates whether the changes conduction times from LSPVp to LAA and HRA (∆LSPVp-LAA and ∆LSPVp-HRA) between before and after the creation of the line as the assessment of bi-directional RL block. Methods 76 de-novo non-paroxysmal atrial fibrillation (nPAF) patients underwent BOXI strategy ablation. We initially intended single ring protocol BOXI for all patients. The activation times were measured at LAA and HRA under LSPV pacing at baseline and after application for the RL. Then we compared the change of activation time at LAA (∆LSPVp-LAA) and at HRA (∆LSPVp-HRA) between 2 groups; the group that completed BOXI with the first-pass roof line (fp-RL group) and the other group (Nfp-RL group). Results In 47 patients, the first-pass roof line was successfully obtained and in patients was done with additional application for gap(s) on the roof line to complete BOXI. There was a stepwise increase in mean ∆LSPVp-HRA not ∆LSPVp-LAA. Increased LA diameter, lower LVEF, and thinner LA wall were associated with the first-pass roof line. ∆LSPVp-HRA ≥33ms predict roof line block with high specificity and sensitivity. Conclusions Our findings suggest that the changes conduction times between LSPV and HRA during LSPV pacing help in the assessment of RL block.