AF is a frequent complication after mitral surgery, even in patients with no prior arrhythmic history, facilitated by left atrial dilation and the structural remodeling associated with valvular disease. In patients with AF, the LAA is the main source of thrombus formation, and its surgical exclusion during cardiac surgery has been shown to significantly reduce the incidence of stroke and systemic thromboembolism when combined with anticoagulation, as demonstrated by the randomized LAAOS III trial. However, extrapolating this benefit to patients in sinus rhythm remains a matter of debate.

In this context, some observational studies have suggested a potential benefit of prophylactic LAA closure in patients without AF undergoing mitral surgery. Among them, the single-center analysis by Chikwe et al. stands out, reporting a reduction in long-term cerebrovascular events after mitral repair with concomitant LAA closure.

Tam et al. evaluated this question using Medicare® administrative data from 2010 to 2019. Among more than 38000 patients undergoing isolated mitral repair, 10810 in sinus rhythm met inclusion criteria after excluding prior cardiac surgery, endocarditis, urgent procedures, and preoperative AF. Of these, 17% underwent concomitant LAA closure. Propensity score matching based on 27 baseline variables yielded 1875 well-balanced patient pairs.

The primary endpoint was stroke or thromboembolism during approximately 5 years of follow-up, with all-cause mortality as a secondary endpoint. Prophylactic LAA closure was associated with a lower cumulative incidence of stroke or thromboembolism at 5 years (6.4% vs 8.3%; p = .023), corresponding to an approximate 25% relative risk reduction. The number needed to treat to prevent one thromboembolic event was 52. However, this did not translate into improved overall survival, which was similar between groups (91% vs 91%; p = .95).

In the matched cohort, there were no differences in 30-day mortality. However, LAA closure was associated with a higher incidence of postoperative AF (45% vs 38%), consistent with prior reports and likely related to increased atrial manipulation.

COMMENTARY:

This study provides meaningful insight in a setting characterized by substantial variability in clinical practice. Its main strengths include a large national sample, multicenter representation, and robust propensity matching. It also reflects a progressive increase in real-world use of prophylactic LAA closure during mitral repair in patients without AF over the study period.

Nevertheless, the study has inherent limitations. It is observational and based on administrative data, without granular information regarding the surgical technique used for LAA closure or long-term anatomical confirmation of effective exclusion. Although subgroup analysis by closure method (device, nondevice, unknown) did not reveal significant differences in thromboembolic events, these findings must be interpreted cautiously due to the lack of imaging validation and potential residual confounding. Importantly, there were no available data on postoperative anticoagulation or antiarrhythmic therapy at discharge. This is particularly relevant given the higher rate of postoperative AF in the closure group, which could have influenced stroke risk and partially mediated the observed benefit.

From a guideline perspective, the 2025 ESC/EACTS valvular heart disease guidelines recommend surgical LAA closure in patients with AF undergoing valve surgery as an adjunct to anticoagulation (Class I, Level B). However, there is currently no specific recommendation for patients without AF, reflecting the absence of randomized evidence supporting a systematic strategy.

In this regard, the ongoing LEAAPS (Left Atrial Appendage Exclusion for Prophylactic Stroke Reduction) randomized trial is particularly relevant. This multicenter study is evaluating whether surgical LAA exclusion during cardiac surgery reduces ischemic stroke or systemic embolism in high-risk patients, including those without documented AF. Its results are expected to clarify whether prophylactic LAA closure should be more broadly incorporated into routine surgical practice.

Several additional considerations merit discussion. First, the present analysis focuses exclusively on mitral repair and excludes patients undergoing mitral valve replacement with prostheses, limiting generalizability to a clinically relevant subgroup. Second, the increased incidence of postoperative AF observed in patients with LAA closure contrasts with certain clinical observations. In practice, some patients with preoperative AF undergoing mitral surgery and LAA exclusión, even without concomitant ablation, convert spontaneously to sinus rhythm postoperatively. This phenomenon may reflect reverse atrial remodeling and reduction in left atrial size after correction of mitral pathology.

From a practical standpoint, stroke risk in this population likely depends on maintenance of sinus rhythm, effective exclusion of the LAA, or the interaction between both factors. Intervening on at least one of these mechanisms may be clinically meaningful. Therefore, prophylactic LAA closure during mitral repair could be considered a reasonable strategy in selected patients, particularly older individuals, those with enlarged left atria, or those with elevated thromboembolic risk scores, especially given that neither this study nor others have demonstrated an increase in operative risk associated with the procedure.

REFERENCE:

Tam DY, Sallam A, Chen Q, Gill G, Kiankhooy A, Fremes SE, et al. Mortality and stroke after routine left atrial appendage occlusion in patients undergoing isolated mitral repair without atrial fibrillation in the United States. J Thorac Cardiovasc Surg. 2025;170:1525–1533. doi:10.1016/j.jtcvs.2025.03.006.