Current ablation practices in patients with durably isolated PVs
The fact that a large portion of patients with recurrent AF have durably isolated PVs indicates that the source of AF must partially be located outside the PVs. The mechanisms of AF in this specific subset of patients are unknown. Although, ablation strategies targeting extra-pulmonary AF foci/triggers have been effective in certain sub-groups of patients, current evidence does not indicate that any individual strategy is more effective than PVI, whether used alone or in combination. This uncertainty explains the lack of consensus on the best ablation strategy for treating these patients, suggesting that an individualized approach may be necessary.
In the recent retrospective PARTY-PVI study, Benali et al. compared outcomes of various ablation strategies during repeat ablation for AF in 367 patients with durably isolated PVs from 39 centers.(10) The majority of patients were male (67%) with persistent AF as dominant recurrence type (56.4%). Most patients received only one ablation strategy (54.5%), followed by two or three (37.1% and 6.5%). Similar to our study, they observed no significant difference in AF-free survival across strategies, with LA size being the only independent predictor of recurrence. In their analyses Benali et al. clustered similar strategies to increase statistical power and therefore did not investigate the individual effect of ablation strategies. Additionally, they did not report data on the incidence of durably isolated PVs relative to all patients undergoing repeat ablation, nor did they specify how many patients received no additional ablation.
Recently, preliminary findings from the ASTRO-AF study were presented.(13) This multicenter, prospective, randomized study compared substrate modification and left atrial appendage isolation in 161 patients with durably isolated PVs.(13) They found no statistically significant difference in AF/AT recurrence at one year between the two ablation strategies. Of note, more than half of the patients had undergone more than one prior ablation procedure. Due to futility, the study was prematurely terminated after randomizing 63% of the planned patient population.
In our study, posterior wall isolation was the predominant strategy (58.4%) employed in patients with durably isolated PVs. The posterior wall is widely accepted as a major extra-PV harbor for AF triggers and drivers, partly attributed to the shared embryological development with the PVs.(22,23) However, conclusive evidence regarding its efficacy beyond PVI alone remains inconsistent and inconclusive, with currently available data showing contrasting results.(24,25)
To date, few studies have reported on the outcomes of repeat ablation in patients with durably isolated PVs. We observed a high rate of atrial arrhythmia recurrence after ablation in these patients (52.8%). In the PARTY-PVI study, Benali et al. observed a recurrence rate of 43.3% at 2 years after repeat ablation, which did not differ significantly between different types of ablations or combinations of them.(10) In the ASTRO-AF study, the recurrence rates of atrial arrhythmias at 1 year were 48.3% for low-voltage area ablation and 44.5% for empirical left atrial appendage isolation, showing no significant difference between the two approaches.(13) De Pooter et al. observed a 39% recurrence rate at 1 year after repeat ablation in patients with durably isolated PVs.(11) During repeat ablation they performed either empirical trigger ablation, which involved isolating the superior vena cava and/or antralization of the PVI lesions, or substrate ablation, which included creating linear lesions at the roof, mitral isthmus, and/or anterior wall. Small single-center series showed similar recurrence rates, with patients undergoing diverse strategies, including extra-pulmonary trigger ablation, CFAE ablation, and linear ablation.(26,27) In contrast to our study, none of the afore-mentioned investigations included a control group of patients who did not undergo additional re-ablation. The lack of evidence so far supporting a particular ablation strategy highlights the importance of including such a control group in future research.