Differences in Post Ablation Cardiac MRI Scar Between Radiofrequency and Cryoballoon Ablation: A DECAAF II Sub-analysis.

INTRODUCTION: Pulmonary vein isolation (PVI) using radiofrequency (RF) and cryoballoon (Cryo) ablation are standard approaches for rhythm control in patients with symptomatic atrial fibrillation. Both strategies create scar in the left atrium (LA). There have been few studies investigating the difference in scar formation between patients undergoing RF and Cryo using cardiac magnetic resonance imaging (CMR).

METHODS: The current study is a sub-analysis of the control arm of the Delayed-Enhancement MRI Determinant of Successful Catheter Ablation of Atrial Fibrillation study (DECAAF II). The study was a multicenter, randomized, controlled, single blinded trial that evaluated atrial arrhythmia recurrence (AAR) between PVI alone and PVI plus CMR atrial fibrosis guided ablation. Pre-ablation CMR and 3-6-month post ablation CMR were obtained to assess baseline LA fibrosis and scar formation respectively.

RESULTS: Of the 843 patients randomized in the DECAAF II trial, we analyzed the 408 patients in the primary analysis control arm that received standard PVI. Five patients received combined RF and Cryo ablations so were excluded from this sub-analysis. Of the 403 patients analyzed, 345 underwent RF and 58 Cryo. The average procedure duration was 146 minutes for RF and 103 minutes for Cryo (p = 0.001). The rate of AAR at ~15 months occurred in 151 (43.8%) patients in the RF group and 28 (48.3%) patients in the Cryo group (p = 0.62). On 3-month post CMR the RF arm had significantly more scar (8.8% vs. 6.4%, p = 0.001) compared to Cryo. Patients with ≥ 6.5% LA scar (p < 0.001) and ≥ 2.3% LA scar around the PV antra (p = 0.01) on 3-month post CMR had less AAR independent of ablation technique. Cryo caused a greater percentage of right and left pulmonary vein (PV) antral scar (p = 0.04, p = 0.02) and less non-PV antral scar (p = 0.009) compared to RF. On Cox regression Cryo patients free of AAR had a greater percentage of left PV antral scar (p = 0.01) and less non-PV antral scar (p = 0.004) compared to RF free of AAR.

CONCLUSION: In this sub-analysis of the control arm of the DECAAF II trial, we observed that Cryo formed a greater percentage of PV antral scar and less non-PV antral scar compared to RF. Post ablation LA scar ≥ 6.5% predicted freedom from AAR, independent of ablation technique. These findings may have prognostic implications in ablation technique selection and freedom from AAR. This article is protected by copyright. All rights reserved.