Reviewer: Dr. Elif Hande Özcan Çetin

Name of the Study: DECAAF II: efficacy of DE-MRI-guided fibrosis ablation vs. conventional catheter ablation of persistent atrial fibrillation

Published Congress: ESC

Background:

The DECAAF study, published in 2014, showed that atrial fibrotic tissue detected by delayed contrast magnetic resonance imaging (MRI) was associated with the likelihood of recurrent arrhythmias in AF patients undergoing catheter ablation. Therefore, evaluating the atrial fibrotic tissue before the procedure and performing atrial fibrosis targeted ablation in addition to pulmonary vein isolation (PVI) may reduce AF recurrence.

Objective:

The DECAAF II study aimed to evaluate the hypothesis that imaging-guided fibrosis ablation in addition to conventional PVI is superior to PVI alone in improving ablation success rates in patients with persistent AF.

Methods:

In the DECAAF II study, 1024 patients with permanent AF from 44 centers worldwide were examined, and 843 eligible patients were included. Participants were randomized into either PVI plus imaging-guided fibrosis ablation (intervention group) or PVI alone (control group). All patients underwent late gadolinium enhancement (LGE)-MRI before ablation and approximately three months after the procedure. This imaging technique creates a 3D fibrosis map of the left atrium with diseased or fibrotic tissue highlighted in green and healthy tissue highlighted in blue. Baseline images were used during the procedure to guide ablation of fibrotic tissue in the intervention group—operators were instructed to cover or surround the fibrotic tissue in the images during ablation in addition to PVI. Operators in the control group were advised to surround only the pulmonary veins without adding additional lesions.

Lesion formation secondary to ablation was evaluated on MRI performed in the third month. The primary endpoint was atrial arrhythmia recurrence (including AF, atrial flutter, or atrial tachycardia) during 12 to 18 months of follow-up. All patients were followed up for atrial arrhythmia recurrence with multiple ECG methods such as 12-lead ECG recordings, Holter recordings, and smartphone ECG devices after ablation.

Results:

The mean age of the participants was 62.1 years, and 78.8% were male. When atrial fibrosis levels were evaluated at baseline, 98 patients (11.6%) were stage I (less than 10% of the total volume of the left atrial wall), 395 (46.9%)patients were stage II (10-20% of the volume of the left atrial wall), 281 (33.3%) participants were stage III (atrial fibrosis covers 20-30% of the volume of the left atrium), and 69 (8.2%) were stage IV (atrial fibrosis >30% of the volume of the left atrium).

Confirming results from the first DECAAF study, baseline fibrosis, particularly at higher levels of fibrosis, was a predictor of AF ablation outcomes.

Median follow-up duration was 12 months. There was no statistically significant difference in the primary endpoint between intervention and control groups in the intention to treat analysis. Atrial arrhythmia recurrence occurred in 175 (43%) patients in the intervention group and 188 (46.1%) patients in the control group (hazard ratio [HR] 0.95; 95% confidence interval [CI] 0.77-1.17; p=0.63).

Subgroup analysis showed a lower rate of atrial arrhythmia recurrence in the PVI plus imaging-guided fibrosis ablation group for patients with stage I or II fibrosis at baseline.

In the as-treated analysis, atrial arrhythmia recurrence was examined according to the proportion of targeted and covered fibrosis assessed by third-month MR images. Imaging-guided fibrosis ablation was significantly beneficial in the group with stage 1 and stage 2 fibrosis at baseline. The HR for targeted fibrosis was 0.839 (95% CI 0.732-0.961; p<0.05) and the HR for the covered fibrosis was 0.841 (95% CI 0.732-0.968; p< 0.05). However, image-guided fibrosis ablation had no benefit on atrial arrhythmia recurrence in patients with stage III or IV fibrosis at baseline.

The complication rate, including stroke, was higher in the image-guided fibrosis ablation group. The higher rates were primarily driven by patients with a high level of fibrosis at baseline.

Conclusions:

According to the intention to treat analysis, image-guided fibrosis ablation in addition to PVI does not improve post-ablation recurrence rates comparing with PVI alone. However, in as-treated analysis, image-guided fibrosis ablation yields a significant improvement in ablation success rates in patients with low-grade fibrosis at baseline.

Interpretation:

The DECAAF II trial results suggest that targeting atrial fibrosis in AF patients with low levels of fibrotic disease (less than 20% of left atrial volume) may improve ablation outcomes. In addition, the findings highlight that PVI should remain the primary ablation strategy in AF patients with high levels of fibrosis at baseline.