Atrial bipolar voltage analysis to assess vein of Marshall ethanol infusion acute effectiveness and its implication in predicting mitral isthmus block.

backgroundThe vein of Marshall (VoM) is a promising therapeutic target for persistent atrial fibrillation (PeAF) treatment. Ethanol infusion into the VoM (VoM-EI) has demonstrated high effectiveness in facilitating mitral isthmus (MI) block, a fundamental part of the anatomical ablation setup for the treatment of PeAF. However, reliable indexes for optimal ethanol delivery are still lacking, and the role of voltage analysis after VoM-EI in predicting MI block has been poorly explored. PURPOSE: To evaluate the role of voltage analysis after VoM-EI in predicting acute bidirectional MI block and the need of coronary sinus (CS) radiofrequency (RF) applications.

methodsFifty-three PeAF patients who underwent catheter ablation were retrospectively enrolled. Left atrial (LA) high-density bipolar voltage mapping was performed before and after VoM-EI. Low voltage areas (LVA) were assessed for all LA maps using the area measurement tool, and the difference in area width between pre- and post-VoM-EI was defined as ∆LVA. An anatomical lesion set including VoM-EI, pulmonary vein isolation (PVI) and linear lesion for dome, lateral MI, and cavo-tricuspid isthmus (CTI) was performed. In case of residual conduction across MI, additional endocardial and/or epicardial ablations approaching the CS musculature were performed. The time required to achieve bidirectional MI block (AblTime-MI) was collected and the VoM length was measured.

resultsForty-eight out of 53 patients enrolled (90.5%) achieved acute bidirectional MI block. After VoM-EI, mean bipolar ∆LVA was 6.6 ± 4.4 cm

conclusionsVoM-EI-induced LA lesions align with VoM trajectory and anatomy. Larger ∆LVA correlates with shorter ablation time for bidirectional MI block and predicts fewer residual epicardial MI gaps requiring RF application in CS musculature. ∆LVA represents a reliable indicator of VoM-EI effectiveness, predicting MI block failure due to epicardial gaps.