LAUSR

Ablation of persistent atrial fibrillation remains a challenge for electrophysiologists. Although various techniques have been proposed in several prospective or retrospective studies, on the test of randomized trials, pulmonary vein isolation (PVI) remains the first‐line strategy for the treatment of patients even with persistent atrial fibrillation. The Star AF 2 study, as well as the Capla study, demonstrated that techniques considered to be established, such as empirical linear ablation, electrogram ablation, or empirical posterior wall isolation, do not improve outcomes compared to a strategy focused solely on PVI. An exception among randomized studies on the subject is the Belief study, which demonstrated that empirical isolation of the left atrial appendage (LAA), as part of a diffuse substrate modification strategy, can improve success rates in patients with long‐standing persistent atrial fibrillation. Despite these promising results, the observation that LAA isolation increases the risk of thromboembolism dampened the enthusiasm. This is the background to the article by Ghannam et al. in this issue of the Journal of Cardiovascular Electrophysiology. In a retrospective study, they report on patients with persistent atrial fibrillation in whom the LAA was accidentally isolated. Their ablation strategy includes several targets in addition to the pulmonary veins: the posterior wall, the mitral isthmus region, and the region surrounding the LAA are ablated with the aim to terminate AF or to reduce the rate of LAA activation. If the LAA is electrically disconnected, ablation is immediately interrupted to allow for reconnection. Nevertheless, in 41 patients, the LAA got electrically isolated, sometimes during ablation of the periauricular region, but more often during ablation even of remote regions from the LAA itself. During follow‐up, despite excellent results with regard to persistent sinus rhythm at 1 year (but multiple procedures were often required), 7 of the 41 patients had thromboembolic complications, mostly during sinus rhythm, in some cases associated with suboptimal anticoagulation. Another patient had to undergo surgical removal of a large LAA thrombus. the rate of cardioembolic complications was significantly higher compared with 82 control patients treated with the same technique but without achieving LAA isolation, regardless of the permanence of sinus rhythm or of the baseline cardioembolic risk profile. The authors conclude that isolation of the LAA can also be achieved by ablation at a relative distance from the LAA itself, and that patients with an isolated LAA should pay particular attention to anti‐coagulation, possibly preferring an interventional LAA occlusion. This study offers several points for discussion. The ablation technique proposed in this study consists of substrate modification with and without incidental LAA isolation. It is well known, that extensive biatrial substrate ablation may lead to LAA isolation and in light of rather disappointing rhythm outcomes this ablation strategy was abandoned by most centers. Recent studies, however, have suggested that substrate ablation tailored to individual low‐voltage areas may be associated with favorable outcomes. The value of intentional (i.e., empirical) LAA isolation was evaluated in several studies either by circumferential ablation, linear Cox‐Maze‐like isolation, or by cryoballoon‐guided LAAI. The rate of freedom from atrial tachyarrhythmias was promising, but regrettably a higher incidence of thromboembolic complications was observed. In this context, interventional LAA closure proved to be superior to OAC alone and must therefore be considered compulsory following electrical LAA isolation. Given the highly invasive character of this approach careful shared decision‐making seems appropriate: LAA isolation should not be incidental, but planned. In case of recurrence despite durable PVI and in case of known or suspected diffuse substrate, patients should be informed about LAA isolation, with the subsequent need for LAA closure. Finally, future randomized clinical studies are required to identify the most successful ablation strategy beyond persistent PVI. With the improvement of ablation technologies and the introduction of new energy sources, the rate of durable PVI after an index procedure is constantly improving. Patients who present with recurrences despite persistent PVI, the so‐called PVI non‐ responders, are a collective that will interest our discussion in the future.