The motivation for this work stems from a commentary on the results of the LAAOS III study, published mid-2021, which led to the inclusion of a class IIa recommendation in the 2021 European guidelines on valvular heart disease, advocating LAA closure during cardiac surgery in patients with a CHA2DS2VAsc score of 2 or higher. This work focuses on a nonsystematic review of the literature, emphasizing anatomical and technical aspects to optimize procedural outcomes, concluding with a review of current evidence and future perspectives.

The authors emphasize that the perspective on LAA closure should shift. Rather than considering it a minor or accessory procedure with a questionable risk-benefit balance due to potential complications and uncertain utility, it should be viewed as a valuable opportunity during cardiac surgery. LAA closure is a simple, safe procedure that significantly and permanently reduces the long-term stroke risk.

COMMENTARY:

We have all heard aphorisms like, “never trust the appendage of an eighty-year-old lady” or “the roof of the left atrium has no friends” during procedures. These phrases originated at the Cleveland Clinic and highlight the care taken in the mitral approach, as they reference two of the most fragile cardiac structures. Given that a surgeon’s experience is forged through complications, whether their own or others’, the lack of evidence supporting LAA closure relegated it for a long time to a class IIb recommendation, where the preferred option was “leave it alone” unless combined with an ablation procedure.

In nonvalvular atrial fibrillation, over 90% of emboli originate in the LAA, and in cases of AF associated with rheumatic valve disease, the rate is between 50% and 75%. In valvular, non-rheumatic AF, the rate lies between these two percentages. In structural heart disease, a minority of emboli originate from sites other than the LAA due to endocardial changes caused by regurgitation jets or inflammatory processes associated with rheumatic disease, creating thrombotic substrates.

Interest in structural interventions for percutaneous LAA closure in nonvalvular AF revived interest in a previously undervalued procedure. Once again, competition with interventional cardiology prompted surgeons to reconsider its importance. Devices like Watchman® and Amplatzer® Amulet® entered the market, and we adopted a classification of the LAA into four morphological types requiring some imagination: chicken wing, cactus, windsock, and cauliflower. Although many of us have seen appendages that do not fit these types, they relate to embolic risk and technical approach.

LAA anatomy includes the ostium, neck, and trabeculated region, which forms and retains clots in AF patients. The four LAA morphologies are classified based on total length and the angle/shape of the trabeculated portion and neck. Morphologies >4 cm include chicken wing and windsock, while <4 cm are cactus and cauliflower, with shorter morphologies carrying higher embolic risk. Longer shapes may have an angle <100º (chicken wing) or >100º (windsock), with smaller angles offering protection against emboli. The cactus and cauliflower types differ in lobule configuration: multiple around a main stem (cactus) or small, unbranched (cauliflower). Thus, in decreasing embolic risk, these morphologies rank as cauliflower, cactus, windsock, and chicken wing, inversely correlated to their frequency in patients: 3%, 19%, 30%, and 48%, respectively.

The goal of LAA closure is to isolate circulation via neck manipulation, leaving a stump <1 cm from the ostium with continuous sealing of the trabeculated area. During this procedure, interference with adjacent structures, particularly the circumflex vessels in the left atrioventricular groove, should be avoided.

Suggested LAA closure techniques are highly variable, likely affecting outcome consistency. Basic techniques include linear suture (simple or double, endocardial or epicardial, with/without excision), intracavitary patching, circumferential ligature, purse-string suture, and the use of staplers or clips. However, endocardial double-suture line or epicardial clip exclusion or excision with subsequent suture line have shown the best results. Although considered equivalent, each approach has pros and cons. The endocardial technique provides sealing close to the ostium but carries a high risk of recanalization. Epicardial exclusion is suitable for any LAA type, is often combined with ablation, and ensures sealing; however, it is more complex and increases bleeding risk, requiring supportive bands and sealants. The AtriClip® has simplified epicardial approaches with open or minimally invasive designs (Pro®, Pro-V®, Pro2®), achieving >95% implant success. Failures primarily involve a residual stump >1 cm, which is preferable to failure from permeability in suture-line closure. In cases of LAA recanalization (endocardial suture or percutaneous closure), the outcome worsens as systemic coagulation increases in the LAA cul-de-sac. Stroke risk rises, not due to an embolus from a millimeter-wide opening but to thromboemboli originating elsewhere or local atherothrombosis in patients with advanced cardiovascular risk and CHA2DS2VAsc scores. For optimal clip positioning, particularly with concomitant ablation, severing the Marshall ligament, which runs between the lateral face of the LAA and the left pulmonary veins, is recommended.

The literature review highlights the work of Friedman et al., the first to demonstrate the benefit of concomitant LAA closure, and Whitlock et al. (LAAOS III), which consolidated guideline recognition. LAA closure almost halved the risk of new ischemic stroke, reducing stroke incidence by 2%. A meta-analysis from our center, also cited in the 2021 European guidelines, demonstrated LAA closure’s protective benefit in patients with bioprosthesis/mechanical prosthesis/valve repair, those undergoing surgical ablation, or following various anticoagulation regimens. Even with continued anticoagulation, LAA closure offers synergistic protection during subtherapeutic anticoagulation periods, especially with vitamin K antagonists. Additionally, LAA closure provides a permanent benefit and reduces the need for interventional procedures if anticoagulation is suspended.

Finally, two controversies arise:

1. The authors question whether excluding the LAA alone is worthwhile without concurrent ablation, given the limited success of concomitant ablation in valvular heart disease AF. They conclude that there is insufficient evidence to make this claim, as no studies specifically address it. Ablation includes LAA exclusion, and while both reduce embolic risk, each has its target and indications, likely making them complementary. Patient selection for ablation plus LAA closure or LAA closure alone is necessary.
2. The LAA serves as a sensor for hypervolemia/volume overload, distending to release atrial natriuretic peptide. Although beneficial effects in AF patients are well-documented, where endocrine function is impaired, recent studies suggest closure benefits for patients in sinus rhythm. Cardiac surgery patients have an increased risk of early or long-term AF development, heightening stroke risk. However, no randomized evidence supports systematic closure. The AtriClip® ATLAS study will address this question. Currently, no recommendation can be made, but for patients losing the LAA, diuretic therapy should be continued short- to mid-term postoperatively until neuroendocrine mechanisms readapt following correction of cardiopathy.

In any case, we can no longer view the LAA as a trivial appendix. It should be a therapeutic target in any AF patient undergoing surgery, providing a clear clinical benefit. The benefit will be permanent and complementary to cardiopathy correction. For example, in mitral insufficiency, the prothrombotic state increases after correcting atrial washout by eliminating regurgitation jets after valve repair or replacement. This is further reason not to leave the appendage open.

REFERENCE:

Badhwar V, Scott Rankin J, Lee R, McCarthy PM, Wei LM. Contemporary left atrial appendage management during adult cardiac surgery. J Thorac Cardiovasc Surg. 2023 Apr;165(4):1398-1404. doi: 10.1016/j.jtcvs.2022.02.029.