Success rates of catheter ablation in persistent atrial fibrillation (AF) remain suboptimal. The DECAAF study previously reported that among patients with AF undergoing catheter ablation, atrial tissue fibrosis, estimated by delayed enhancement cardiac magnetic resonance (CMR), was independently associated with the likelihood of recurrent arrhythmia.1
In a Hot Line session today, Professor Nassir Marrouche (Tulane University, New Orleans, USA) presented findings from the prospective DECAAF II trial, which investigated whether imaging-guided fibrosis ablation in addition to pulmonary vein isolation (PVI) is superior to PVI alone in improving ablation success rates in patients with persistent AF.
DECAAF II randomised 843 patients with persistent AF undergoing a first-time ablation procedure to either PVI plus imaging-guided fibrosis ablation (intervention group) or PVI alone (control group). Left atrial fibrosis and ablation-induced scarring were defined by late gadolinium enhancement (LGE)-CMR at baseline and at ~3 months postablation, respectively. “These unique data provide us with the opportunity to better understand the effect of ablation on the left atrium and what parameters influence the formation of an ablation lesion,” said Prof. Marrouche.
Participants were followed for the primary endpoint of atrial arrhythmia recurrence (including AF, atrial flutter or atrial tachycardia) for 12 to 18 months. Atrial arrhythmia recurrence was detected through 12-lead ECG recordings, Holter recordings and a smartphone ECG device given to all patients after ablation.
The average age of participants was 62.1 years and 78.8% were men. Regarding atrial fibrosis levels at baseline, 11.6% of patients had stage I (<10% of the total volume of the left atrial wall), 46.9% had stage II (10–20%), 33.3% had stage III (20–30%) and 8.2% had stage IV (>30%). Baseline fibrosis was predictive of AF ablation outcomes, especially at higher fibrosis levels, confirming the results of the initial DECAAF study.
The median follow-up was 12 months. The intention-to-treat analysis showed no significant difference in atrial arrhythmia recurrence, which occurred in 43.0% patients in the intervention group and 46.1% patients in the control group (hazard ratio [HR] 0.95; 95% confidence interval [CI] 0.77 to 1.17; p=0.63). In subgroup analyses, a trend was observed towards a lower rate of atrial arrhythmia recurrence in the intervention group for patients with stage I or II fibrosis at baseline.
As-treated analyses examined atrial arrhythmia recurrence according to the proportion of targeted and covered fibrosis (as assessed by the 3-month CMR). There was a significant benefit of substrate ablation in patients with stage I or II fibrosis at baseline, with HR 0.839 (95% CI 0.732 to 0.961; p<0.05) for targeted fibrosis and HR 0.841 (95% CI 0.732 to 0.968; p<0.05) for covered fibrosis. However, there was no benefit in patients with stage III or IV fibrosis at baseline.
The rate of complications, including post-ablation stroke, was higher in the image-guided ablation group, but was mainly driven by patients with high levels of fibrosis at baseline.
Summarising the findings, Prof. Marrouche said, “The results suggest that targeting atrial fibrosis in AF patients with low levels of fibrotic disease (less than 20%) may help improve ablation outcomes. In addition, the findings indicate that PVI should remain the mainstream ablation strategy in AF patients with high levels of fibrosis (more than 20%).”
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