Local Impedance Drop Predicts Durable Conduction Block in Patients With Paroxysmal Atrial Fibrillation

Objective: This study was performed to evaluate the performance of local impedance (LI) during pulmonary vein isolation (PVI) in paroxysmal atrial fibrillation patients. Acute analysis demonstrated that LI drop was predictive of PVI segment conduction block. Subsequent analysis of durable block based on a 3-month mapping procedure was performed to assess the translation to mature lesion formation. Methods: Fifty-eight patients who had undergone LI-blinded de novo PVI returned for a 3-month mapping procedure. PVI ablation circles were divided into 16 anatomical segments for classification (durable block or gap) and the median LI drop within segments with inter-lesion distance (ILD) ≤6mm was compared. The association between starting LI and optimal LI drops was also examined. Results: LI drop outperformed generator impedance drop as a predictor of durable conduction block (AUC: 0.79 vs 0.68, p=0.003). Optimal LI drops were identified as a marker for durable block that suitably balanced sensitivity and specificity by region (Anterior/Superior:16.9Ω [Sensitivity:69.1%, Specificity:85.0%, Positive Predictive Value (PPV) for durable conduction block:97.7%] and Posterior/Inferior:14.2Ω [Sensitivity:73.8%, Specificity:78.3%, PPV:96.9%]). LI prior to RF application was significantly different between healthy, gap and mature scar tissue, and was also a contributing factor to achieving an optimal LI drop (85.2% of RF applications with a starting LI ≥110Ω achieved at least the optimal drop). Conclusion: This study demonstrates that LI drop is predictive of durable PV segment isolation and supports a regional approach to RF energy titration guided by LI drop combined with careful ILD control. (NCT03232645)