Atrial fibrillation (AF) ranks among the most common arrhythmias and carries a substantial risk of adverse events, chiefly because of the elevated risk of cardioembolic stroke. Surgical left atrial appendage closure (LAAC) is indicated in patients with AF undergoing cardiac surgery (class I recommendation, level of evidence B, per the 2023 clinical practice guidelines of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS)). Nonetheless, the evidence supporting the success of surgical LAAC remains limited and heterogeneous, owing to the wide array of available closure techniques, the lack of a universally accepted definition, and the modest sample sizes of the studies conducted to date.

This review pursued three aims: (1) to identify and describe the methods used to evaluate LAAC; (2) to describe any published validation of these evaluation methods and their criteria; and (3) to report success rates of surgical LAAC according to the different imaging modalities employed and the various assessment time points.

A systematic literature search was conducted across the Embase, MEDLINE, and Cochrane Library databases in November 2024. The search strategy was built around two main components: (1) how LAAC had been performed; and (2) the imaging technique used to assess LAAC. Inclusion criteria comprised: (1) clinical studies enrolling patients who underwent surgical LAAC, whether by amputation with suture closure, stapled closure, suture closure without amputation, and/or closure with an approved surgical occlusion device (e.g., AtriClip®); and (2) studies including an intraoperative or postoperative evaluation of surgical LAAC success. Studies were excluded if they were: (1) case reports or series with fewer than 10 participants; (2) articles whose full text was unavailable in German, English, Danish, Swedish, or Norwegian; or (3) animal studies.

A total of 8737 references were screened, of which 186 studies underwent full-text review; 80 studies ultimately met the inclusion criteria. Most were observational studies (96%), while only 3 were randomized clinical trials (4%). The included studies originated from 19 different countries, with 5 being international multicentre studies. Overall, 7517 patients and 10375 imaging examinations were analysed. Transoesophageal echocardiography (TEE) was the imaging modality most commonly used (83%), predominantly for intraoperative assessment, whereas cardiac computed tomography (CT) was used in 44% of studies for postoperative evaluation. Seventeen distinct definitions of procedural success were identified; the criteria applied most often were the absence of persistent residual flow between the left atrium and the LAA and a residual LAA stump <10mm. Across all imaging modalities, assessment time points, and criteria combined, the overall procedural success rate was 92.8%. Success rates were highest during intraoperative assessment (96.8%) and declined progressively as the time elapsed since the procedure increased.

COMMENTARY:

The randomized LAAOS III trial showed that LAAC, added to oral anticoagulation, lowers the risk of stroke and systemic embolism in patients with AF. This thromboembolic benefit, however, hinges on the closure having been achieved correctly. Even so, no universally accepted definition of LAAC success currently exists. The 2023 American College of Cardiology recommendations regard absence of residual flow together with a residual stump below 10mm as markers of success, in line with the criteria applied in the LAAOS III trial. By contrast, the 2024 European guidelines do not put forward a specific definition of success, while the 2023 Society of Thoracic Surgeons recommendations regard complete obliteration of the LAA as the marker of success. This lack of agreement over what constitutes effective closure underscores the absence of uniform, standardized criteria for evaluating the success of surgical LAAC.

LAAC can be achieved through several closure mechanisms; all are suitable for on-pump cardiac surgical procedures, whereas epicardial clips are better suited to off-pump or thoracoscopic approaches. A residual stump below 10mm, although widely adopted as a marker of LAAC success, has limited validity and varies considerably depending on the imaging technique and measurement method used. Its clinical relevance also appears to depend on the closure technique applied, so this parameter may not be uniformly applicable across all procedures. Against this backdrop, persistent communication or residual flow between the left atrium and the LAA may represent a more meaningful marker of incomplete closure, given its consistent association with a higher risk of stroke, systemic embolism, and other thromboembolic events. While evidence from percutaneous techniques cannot be directly extrapolated to surgical exclusion, these findings support the clinical relevance of residual flow as a potential marker of procedural success. Concomitant surgical ablation of AF is another important consideration, as it may lower mortality and stroke risk: restoring sinus rhythm alters atrial haemodynamics and, in turn, reduces the propensity for thrombus formation, independent of the anatomical efficacy of LAAC.

Although the authors offer a comprehensive synthesis of the available evidence, the findings warrant cautious interpretation given several limitations. The evidence base is predominantly observational, with few randomized trials and a substantial proportion of isolated case series. Furthermore, the apparent decline in closure success observed during follow-up may reflect selection bias, since imaging studies are typically performed on clinical grounds rather than as part of an active surveillance protocol. Lastly, differences in the imaging modality and timing of assessment may affect estimated procedural success rates, as TEE may underestimate residual leaks relative to cardiac CT, which allows a more comprehensive volumetric assessment and offers greater sensitivity for their detection.

In summary, improving surgical LAAC outcomes calls not only for refining the devices and surgical strategies currently available, but also for establishing consistent criteria to evaluate procedural results. Future research should focus on defining and validating standardized criteria for surgical LAAC success, grounded in clinically meaningful variables capable of accounting for the differences inherent to each device and closure modality, so as to ensure that what is being done is, in fact, being done well.

REFERENCE:

Vad R, Gosvig K, Beetham R, Hansson NH, Whitlock R, Riber LPS. Methods and Criteria for Evaluating the Success of Surgical Left Atrial Appendage Closure: A Systematic Review. Eur J Cardiothorac Surg. 2026 May 11;68(5):ezag146. doi: 10.1093/ejcts/ezag146.

Servito M, Vallamkonda S, Fremes SE. More Questions Than Answers: The Elusive Meaning of Success in Left Atrial Appendage Closure. Eur J Cardiothorac Surg. 2026 May 11;68(5):ezag169. doi: 10.1093/ejcts/ezag169.