Stepwise Catheter Ablation Named Winner for Persistent Afib

Among catheter ablation strategies for persistent atrial fibrillation (Afib or AF), the stepwise electro-anatomical guided approach emerged victorious based on head-to-head comparisons in a small randomized trial.

After a single ablation procedure and without anti-arrhythmic drugs, 72% of patients subject to the stepwise ablation strategy achieved 12-month freedom from Afib lasting longer than 30 seconds, which was significantly more than the 54% of peers receiving anatomical-guided ablation (P=0.002). The extensive electro-anatomical strategy also trended better than electrogram-guided ablation without reaching significance (72% vs 64%, P=0.116).

Afib termination was more likely with the stepwise (66.7%) and electrogram-guided approaches (56.7%) compared with the anatomical strategy (20.7%). This is notable because achievement of Afib termination was associated with lower Afib recurrence at 12 months (30.1% vs 42.7% without Afib termination, P=0.008), suggesting it is a reliable ablation endpoint.

"We found that, among the three strategies, electro-anatomical guided ablation achieved the highest rate of AF termination and the lowest rate of AF recurrence despite a longer procedure time being required," reported study authors Xu Liu, PhD, of Shanghai Chest Hospital, Shanghai Jiao Tong University, and colleagues in Europace.

"Based on our findings, we concluded that extensive ablation targeting electro-anatomical mechanisms to pursue AF termination is the optimal strategy for [persistent Afib]," the investigators wrote.

Electrophysiologists have long sought to improve the performance of catheter ablation of persistent Afib, a setting in which the technology has not replicated the success for paroxysmal Afib.

This gave rise to the anatomically- and electrogram-guided adjuncts to basic pulmonary vein isolation (PVI) assessed by Liu and colleagues in their trial:

• The anatomically-guided protocol comprised linear left atrial posterior box isolation and mitral isthmus linear ablation, with some patients in this group also getting vein of Marshall ethanol infusion
• In atrial electrogram-guided ablation, point-by-point radiofrequency applications were performed to achieve a complete flattening of the bipolar signal amplitude
• Finally, the extensive ablation group received stepwise electrogram-guided ablation followed by anatomical-guided ablation; if Afib terminated during the former approach, the operator still went forward with the latter

The downside of stepwise combination ablation is that it may create unnecessary proarrhythmic scars.

However, Liu's group reported that the extensive ablation strategy (50%) fell between electrogram-guided ablation (60%) and anatomical ablation (37.3%) in terms of combined Afib and atrial tachycardia recurrence. Moreover, safety endpoints did not differ significantly among the three groups.

"Currently, there are still no large-scale, multicenter, randomized studies that directly compare the efficacies of the three ablation strategies, and ablation strategies remain uncertain in the present guidelines," the authors wrote.

Recently, linear posterior wall isolation was found to be no better than PVI alone for persistent Afib in the CAPLA study.

The older STAR AF II trial had shown no improvement in outcomes between PVI alone, PVI with linear ablation, and PVI with electrogram ablation. Notably, the combined stepwise approach was not tested in this study.

For the present study, Liu's group enrolled 450 persistent Afib patients from 2019 to 2020 and randomized them to one of the three ablation protocols of the study.

The three groups were well balanced at baseline. Age was 65.8 years on average, with nearly 70% of the cohort being men. Approximately half of participants had longstanding Afib.

Outpatient visits and 48-h Holter monitoring were scheduled at 1, 3, 6, 9, and 12 months, and every 6 months thereafter if the patient remained asymptomatic. Recurrent atrial arrhythmia was defined as any episode lasting 30 seconds or more on ECG or Holter monitoring.

Without the use of implantable event recorders, however, some asymptomatic Afib episodes may have gone undetected, investigators acknowledged.

Furthermore, the study did not capture late arrhythmias beyond 12 months and lacked a PVI-alone group for control.

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