Lesion Delivery and Scar Formation in Catheter Ablation for Atrial Fibrillation The DECAAF II Trial.

Abstract

Background: The DECAAF-II randomized trial showed no difference in AF recurrence with additional delayed enhancement MRI (DE-MRI) fibrosis-targeted ablation to pulmonary vein isolation (PVI) in persistent AF.

Objectives: We evaluated the impact of lesion delivery on ablation-induced scarring and AF recurrence.

Methods: Lesions delivered, targeting fibrotic and non-fibrotic areas identified from pre-ablation DE-MRI, were studied in relation to ablation-induced scarring on 3-months DE-MRI, including their association with arrhythmia recurrence.

Results: 593 patients, treated with radiofrequency were analyzed: 293 underwent PVI and 300 underwent additional fibrosis-guided ablation. Lesion analysis showed that 80.9% in the MRI fibrosis-guided group vs 16.5% in the PVI group (p<0.001), had ≥ 40% of baseline fibrosis targeted. MRI assessment of ablation-induced scar showed that 44.8% of fibrosis-guided ablation and 15.5% of PVI had ≥ 40% of their fibrosis covered by scar (P<0.001), demonstrating a significant attenuation from lesions delivered to scar formed. In the overall population, fibrosis coverage with scar was not associated with recurrence (HR 0.90, 95% confidence interval [CI] 0.80-1.01, p = 0.08 per 20% increase). In patients with baseline fibrosis <20%, fibrosis coverage with scar was associated with lower recurrence than PVI (HR 0.85; 95% CI [0.73-0.97]; p=0.03), whereas the association was not significant when baseline fibrosis ≥20% (HR 0.97; [0.80-1.17], p=0.77). Significant center variation was observed in fibrosis targeting and coverage with scarring.

Conclusions: Radiofrequency ablation lesions do not uniformly result in scar formation. Post hoc analysis suggests reduced arrhythmia recurrence when ablation-induced scarring covers fibrotic regions in patients with low baseline fibrosis.