Left Atrial Appendage Occlusion: A Simple Idea Without a Simple Technique

There has been much interest in getting rid of the left atrial appendage (LAA) to prevent embolic strokes in patients with atrial fibrillation. During cardiac surgery, it can be cut off, or excluded using staples, sutures, or a clamp-like device. It seems like surgery should be fairly definitive. However, it turns out that unless the LAA is completely removed, there is a surprisingly high rate of persistent communication between the LAA and the left atrium. In a study from the Cleveland Clinic, successful complete LAA closure occurred in only 23% of patients who underwent suture exclusion of the LAA, and in no patients who underwent stapler exclusion.¹ They also found LAA clot in 41% of patients with an unsuccessful LAA exclusion compared to no patients who underwent excision. If the LAA cannot be occluded surgically with the chest opened, it seems that it will be difficult to occlude percutaneously.

Nonetheless, a few percutaneous methods of LAA occlusion that use an endocardial plug-like device are under investigation. The WATCHMAN device is currently being implanted as part of a second large trial in the United States, after the FDA did not approve it initially; the WATCHMAN device was recently acquired by Boston Scientific Corporation. The failure to gain FDA approval appeared to be based on a relatively high intraprocedural complication rate. However, there are also new concerns about the ability of the device to occlude the appendage over the long term. In November 2011, Bai et al published a study that included 58 patients who had undergone implantation of the WATCHMAN device implant and had intraprocedural, 45-day, and 12-month transesophageal echocardiogram images for review.² A gap was noted around the occlusion device in 28%, 29%, and 35% of the patients at each time interval, respectively. Intraprocedural gaps were more likely to be persistent at 12 months, and became larger in size over time. In addition, new gaps also occurred during follow-up even when the LAA was completely sealed at the time of implantation. A second LAA occluder device, an Amplatzer-like device, is also being implanted as part of an investigational trial in the United States; this device was recently acquired by St. Jude Medical.

So while Boston Scientific and St. Jude Medical are busy working to determine if the LAA can safely and effectively be occluded and reduce the risk of stroke in patients with AF, one must also take note of SentreHEART’s LARIAT Suture Delivery Device. Unlike an endocardial occluder device, the LARIAT is a catheter-based suture delivery system that uses a snare. It has been shown in animals to safely and reliably suture the LAA shut from the outside using a combined endocardial and epicardial access.³ Several hundred procedures have been performed already in Europe, and nearly 200 procedures have been performed in the Unites States at select centers.

Based on the knowledge that when clots form in the atrium in patients with AF, the clots are usually in the LAA, it is logical to develop ways to close the LAA to prevent stroke in patients with AF. However, it appears to be more difficult than previously thought to achieve LAA occlusion. Only until the LAA can be reliably occluded, will we know whether or not LAA occlusion can prevent strokes. The newly available epicardial snare-based ligation approach is attractive, but it remains to be determined whether or not the LAA will remain closed over time, and if it can prevent strokes.

References

1. Kanderian AS, Gillinov AM, Pettersson GB, et al. Success of surgical left atrial appendage closure: Assessment by transesophageal echocardiography. J Am Coll Cardiol. 2008;52:924-929.
2. Bai R, Horton RP, DI Biase L, et al. Intraprocedural and Long-Term Incomplete Occlusion of the Left Atrial Appendage Following Placement of the WATCHMAN Device: A Single Center Experience. J Cardiovasc Electrophysiol. 2011 Nov 14. doi:10.1111/j.1540-8167.2011.02216.x
3. Lee RJ, Bartus K, Yakubov SJ. Catheter-based left atrial appendage (LAA) ligation for the prevention of embolic events arising from the LAA: Initial experience in a canine model. Circ Cardiovasc Interv. 2010;3:224-229.