The LAA is the primary site of thrombus formation in patients with atrial fibrillation (AF), contributing to over 90% of embolic strokes in this population. LAA closure has emerged as a valuable therapeutic alternative for selected AF patients. Percutaneous devices such as the WATCHMAN™ (Boston Scientific™) allow for percutaneous LAA occlusion; however, various studies estimate a high thrombosis rate (7.2% annually), resulting in an increased stroke rate. 

Consequently, with the advent of other devices, including automatic staplers and clipping systems like the AtriClip™ (AtriCure™), which exhibit lower thrombosis rates than endovascular devices (although not exempt from it, as discussed in previous entries on this blog), attention has shifted not only to LAA closure during conventional cardiac surgeries but also to thoracoscopic procedures with or without AF ablation. Some studies place the AtriClip™ system in a favorable position regarding effective closure results and a lower tendency to develop thrombosis, as it avoids endocardial damage by not piercing the atrial wall, unlike automatic staplers, and does not contact blood continuously as endovascular devices like the WATCHMAN™. With this context and recognizing that the critical point for effective thromboembolic prevention is complete LAA closure, this study aimed to compare the AtriClip™ with an automatic stapler system to shed light on this question. 

To this end, the study included 333 patients who underwent thoracoscopic AF ablation and LAA closure from February 2012 to October 2020. Propensity score matching in a 4:1 ratio paired 90 patients with LAA clipping (AtriClip™) with 206 patients with stapled resection (Endo GIA™, Tyco Healthcare Group™). The primary objective was complete LAA closure, defined as a residual LAA depth of less than 1 cm in CT images obtained one year postoperatively. 

No deaths occurred within 30 days. Complete LAA closure was achieved in 85.9% (286 of 333) of patients. After propensity score matching, the AtriClip™ group demonstrated a significantly higher rate of complete LAA closure compared to the stapler resection group (95.6% vs. 83.0%; p = .003), as well as a lower residual LAA stump depth (2.9 vs. 5.3 mm; p = .001). 

After 4 years of clinical follow-up, the stroke incidence was 0.76% per year in the stapler group and 0.97% per year in the AtriClip™ group. A residual LAA stump was found in 2 patients who developed strokes. Long-term follow-up indicated that 82% of patients could discontinue oral anticoagulants. 

The authors concluded that the AtriClip™ group demonstrated a higher rate of complete LAA closure compared to the stapler resection group. Close monitoring of patients with residual LAA stumps is essential. Further research with larger cohorts is needed to elucidate the impact of the residual LAA stump on thromboembolic events. 

COMMENTARY: 

The clinical benefits of LAA closure are increasingly clear, despite recent uncertainties. Since 2017, the Society of Thoracic Surgeons (STS) clinical practice guidelines have recommended (class IIa) LAA closure for thromboembolic prevention. However, it was not until 2021, with the publication of the LAAOS III study (The Left Atrial Appendage Occlusion Study), that surgical LAA closure was demonstrated to provide protection against ischemic strokes and systemic embolism in AF patients. The absence of clear evidence prior to this study may be partly due to the use of various LAA closure techniques. Thanks to the LAAOS III study, the 2023 ACC/AHA/ACCP/HRS guidelines currently recommend class I LAA closure during cardiac surgery for patients with a CHA2DS2-VASc score ≥2 and class IIa for percutaneous closure in patients contraindicated for anticoagulation. 

The ideal technique for effective LAA closure remains a topic of debate. Our traditional internal suture technique, the most commonly employed method, has proven ineffective in a significant percentage of cases (up to 24%). Other techniques, such as staplers that resect the LAA tissue, prevent recanalization and increase closure success rates. However, they may leave a suboptimal residual stump. Lastly, the latest system, which excludes the LAA through clipping, such as the AtriClip™, appears to demonstrate a higher rate of effective closures. In this vein, the present study provides two key takeaways: 

1. This study is the first to clearly and significantly demonstrate a higher rate of effective closure with the AtriClip™ compared to automatic staplers, with a smaller residual stump. 
2. Oral anticoagulation was discontinued in 82% of patients in the long-term follow-up. 

In my opinion, the higher success rate with the AtriClip™ may be associated with several factors:

• Reduced Endocardial Damage: As noted in the introduction, the AtriClip™ system does not damage the endocardium by avoiding wall penetration, which results in reduced thrombosis formation.

• Design and Versatility: The AtriClip™ port is smaller, and its release system offers greater maneuverability compared to automatic staplers, enabling better positioning and release at the LAA base.

Residual flow from the left atrium into the LAA after incomplete closure, along with a residual stump larger than 1 cm, has been associated with an increased risk of thrombosis, even greater than if no procedure were performed. In this study, the absence of a significant stump and an individualized low CHA2DS2-VASc score were the criteria used for discontinuing anticoagulation. Specifically, 82% of patients maintained no anticoagulation with a very low stroke rate. 

Aside from being a single-center retrospective study with a relatively small sample size, there are additional limitations to consider. These include the lack of information on LAA morphology, which is crucial for determining closure difficulty. Moreover, the limited experience in analyzing stapler results, as staplers were predominantly used in the first five years, also constitutes an important limitation. Since 2017, the use of AtriClip™ has been predominant, which may also have influenced the results. 

In conclusion, I would like to sendo two last messages: 

• The new class I recommendation for LAA closure during cardiac surgery in AF patients with a CHA2DS2-VASc score ≥2 requires us, as surgeons, to perform LAA closure, either through direct suture or with percutaneous devices. Based on the available evidence, which I have summarized here, I would undoubtedly choose the AtriClip™ system. 

• Furthermore, in a specialty like ours, which has undergone significant changes in recent years and faces constant competition from interventional cardiology, it is crucial to stay current with the latest scientific evidence and be innovative in adopting new minimally invasive techniques that simplify and enhance procedures. We cannot make excuses for not adopting techniques such as thoracoscopic surgery and other emerging innovations when new devices and expanded surgical indications arise. We must embrace all new technologies available to benefit our patients, for “he who does not know what he wants ends up where he does not want to be.” 

REFERENCE: 

Lim SK, Kim CH, Choi KH, Ahn JH, On YK, et al. A Comparative Study of Thoracoscopic Left Atrial Appendage Clipping vs Stapled Resection. Ann Thorac Surg. 2024 Jun;117(6):1230-1236. doi: 10.1016/j.athoracsur.2023.09.010.