Snaring Atrial Fibrillation

There has been much progress in the development of nonpharmacological therapeutic options for patients with atrial fibrillation (AF) to prevent stroke focused on removal or exclusion of the left atrial appendage (LAA). For example, after many years of clinical trials, the WATCHMAN LAA closure device (Boston Scientific) is now commercially available for patients who are at high risk for stroke but who also have contraindications to long-term oral anticoagulation. In addition, there is increasing interest in the role of the LAA not only as a source of thromboembolism, but as a source of AF initiation and maintenance.

The LAA is the source of ectopy in some patients with AF, and it represents a relatively large mass that could harbor reentrant circuits and rotors. Electrical isolation of the LAA could help prevent AF, and can be accomplished with an ablation catheter. However, circumferential point-by-point radiofrequency catheter ablation at the base of the appendage is technically challenging, not clearly durable, and leads to a noncontractile, static appendage. Data indicating preserved LAA transport function after electrical isolation is difficult to comprehend if the appendage is truly electrically silent. In fact, data that show preserved LAA velocities by echo-Doppler after purported acute electrical isolation should be interpreted as an indication of conduction recovery. Managing a noncontractile LAA with an occluder device is one option, and studies using such a strategy are being planned.

An alternative approach to electrically silence the LAA is to percutaneously snare it. There are data demonstrating that snare closure of the LAA using the LARIAT Suture Delivery Device (SentreHeart, Inc.) produces an acute reduction in the LAA voltage and inhibits the capture of the left atrium during LAA pacing.¹ There are also data that support using LAA ligation in addition to pulmonary vein antral isolation (PVAI) to improve the long-term outcome in patients undergoing catheter ablation for persistent AF. The Left Atrial Appendage Ligation and Ablation for Persistent Atrial Fibrillation (LAALA-AF) Registry was a nonrandomized study that showed that freedom from AF at 1 year (off antiarrhythmic therapy after 1 ablation procedure) was higher in the LARIAT group compared to the ablation-only group (65% vs 39%; P = 0.002), and more patients in the ablation-only group underwent repeat ablation because of AF recurrence (16% vs 33%; P = 0.018).² Based on these findings, the manufacturer of the LARIAT system is sponsoring a randomized trial of staged LAA ligation before PVAI in patients with persistent AF. The trial, which has already begun enrolling patients, is named the aMAZE Trial: Left Atrial Appendage Ligation with the LARIAT Suture Delivery System as Adjunctive Therapy to Pulmonary Vein Isolation (PVI) for Persistent or Longstanding Persistent Atrial Fibrillation.

Despite the enthusiasm for both the concept of LAA ligation to treat persistent AF and the aMAZE trial itself, a recent study has called this strategy into question. A randomized controlled trial by Romanov et al compared thorascopic surgical ablation for patients with persistent AF with or without LAA excision using similar lesion sets that included PVAI and a left atrial box lesion, and found no difference in outcomes as measured by freedom from AF.³ At 18 months, 78% of the LAA removal arm and 76% of the control arm were free of AF without antiarrhythmic drugs (AADs) (P = 0.72). Based on this study, can one conclude that snare closure of the LAA will not improve outcomes when added to catheter-based PVAI for persistent AF? Not necessarily — for at least two reasons. The first reason is that the appendage in the surgical trial was removed using a linear stapler. It is clear from the literature, and from simple observation of the procedure, that this technique often leaves a sizable LAA stump. Snaring the appendage typically results in a more proximal closure that is closer to the base and might result in a different outcome. A second reason is that the outcome of the patients with persistent AF in the surgical study who did not undergo removal of the appendage, as with many published AF surgical outcomes, was much higher that with catheter ablation. Therefore, one cannot conclude that snaring the appendage will not be able to improve the outcomes of catheter ablation even if it does not improve the outcomes of surgical ablation.

Most would agree that better solutions are needed for patients with persistent and longstanding persistent AF. Suture snare of the LAA as a supplement to PVAI might be at least a partial solution, and it might also come with the added benefit of stroke reduction. With hope, the results of the aMAZE Trial will amaze us.

References

1. Han FT, Bartus K, Lakkireddy D, et al. The effects of LAA ligation on LAA electrical activity. Heart Rhythm. 2014;11(5):864-870. doi: 10.1016/j.hrthm.2014.01.019. 
2. Lakkireddy D, Mahankali AS, Kanmanthareddy A, et al. Left Atrial Appendage Ligation and Ablation for Persistent Atrial Fibrillation: The LAALA-AF Registry. JACCCEP. 2015;1(3):153-160. doi:10.1016/j.jacep.2015.04.006.
3. Romanov A, Pokushalov E, Elesin D, et al. Effect of left atrial appendage excision on procedure outcome in patients with persistent atrial fibrillation undergoing surgical ablation. Heart Rhythm. 2016 May 12. pii: S1547-5271(16)30274-0. doi: 10.1016/j.hrthm.2016.05.012. [Epub ahead of print].