Surgeons’ interest in the left atrial appendage (LAA) dates to 1949, when John L. Madden published a paper titled “Resection of the left auricular appendix: A prophylaxis for recurrent arterial emboli.” In that communication, he described two cases in which patients had had embolic events, noting that pathologic examination revealed LAA thrombus in both patients. Writing that “ in about 90 per cent of the cases the mural thrombi are located in the auricles, mainly in the left auricle and its appendix ,” he concludes his discussion with the comment, “ Resection of the left auricular appendix is suggested as a prophylaxis for recurrent emboli. ” Seventy-five years later, we have data to support this statement. Termed “ our most lethal human attachment ” by Dudley Johnson, the LAA has captured the interest of both surgeons and cardiologists in recent years. With an understanding of the increased stroke risk in those with atrial fibrillation (AF) and the pathogenesis of these events, surgeons and interventionalists have deemed the LAA a target for both primary and secondary stroke prevention in patients with AF. There can be no doubt that this interest will grow and that greater numbers of patients with AF will have management plans that address the LAA.
As the number of patients with AF continues to increase, the two questions that surgeons face regarding LAA management are “when” and “how.” When should the surgeon treat the LAA? And how should they address this delicate structure?
When Surgeons Should Manage the Left Atrial Appendage
When contemplating LAA management, surgeons can divide patients into two groups: (1) those with preexisting AF and (2) those with no known history of AF.
Patients With Preexisting Atrial Fibrillation: Concomitant Procedures
In the concomitant setting, surgeons encounter large numbers of patients who have AF in addition to structural heart disease. Supported by a wide body of literature, the Cox Maze procedure, which includes LAA management, is clearly the best approach to these patients. , , The risk of embolic stroke after a Cox Maze procedure is remarkably low, , and restoration of sinus rhythm is achieved in the majority of patients. , Although there is some controversy concerning the relative impacts of the lesion set versus LAA management in this reduced stroke risk, there can be no doubt that proper management of the LAA plays an important role. ,
Nearly all guidelines recommend surgical ablation, including LAA management, at the time of concomitant surgery in patients with preexisting AF. Nevertheless, historically, a majority of cardiac surgery patients with AF have not received ablation. , Fortunately, recent data recommend the increased use of ablation plus LAA management in cardiac surgical patients with AF. In the future, this proportion will continue to increase, particularly if concomitant surgical ablation in those with AF becomes a quality metric.
Meanwhile, based on Whitlock’s landmark Left Atrial Appendage Occlusion Study (LAAOS)-III trial demonstrating that LAA treatment reduces stroke and systemic thromboembolism in cardiac surgical patients with preexisting AF and risk factors for stroke, surgical management of the LAA as a concomitant procedure in patients with AF has become widespread. It received a Class IA recommendation in the 2023 American College of Cardiology/American Heart Association/American College of Clinical Pharmacy/Heart Rhythm Society Guidelines for the Diagnosis and Management of Atrial Fibrillation and in the 2023 Society of Thoracic Surgeons Clinical Practice Guidelines for the Surgical Treatment of Atrial Fibrillation. This important change in the guidelines will certainly generate an increase in surgical management of the LAA in patients with AF. The danger, though, is that surgeons may deem LAA management to be sufficient in their patients with AF and consequently forego ablation. This would be a mistake because the combination of ablation with LAA management is superior to LAA management alone, , , with the former strategy (ablation plus LAA management) associated with improved survival compared with LAA treatment alone.
Patients With Preexisting Atrial Fibrillation: Sole Left Atrial Appendage Management
Thoracoscopic LAA management as an isolated procedure has been reported by several groups over the past two decades. , With port-based access via the left chest and a posterior pericardiotomy, most procedures involved application of either a suture to snare the appendage or a stapler to excise it. Occasionally, problematic bleeding occurred. Now that surgeons have access to LAA clips designed specifically for thoracoscopic application, procedural safety has been enhanced. , Although there will likely be an uptick in surgical sole LAA management, the widespread availability of endovascular devices designed to plug or occlude the appendage will limit surgical involvement to those patients who are not candidates for an endovascular approach or who prefer a surgical approach.
Although current endovascular LAA occlusion (LAAO) devices have improved safety and efficacy profiles compared with earlier generations, they can still engender early and late complications. Although early complications are typically procedural (e.g., perforation and pericardial effusion), late complications are generally caused by device-related thrombus or peri-device leaks that increase stroke risk. Here, epicardially placed surgical devices have an advantage because they completely exclude the appendage and do not include an endovascular component that can be a nidus for thrombus formation.
Patients Without Preexisting Atrial Fibrillation
Now that device-based LAA exclusion is simple, quick, and relatively complication free, some surgeons exclude the LAA in all patients who undergo a sternotomy, even if the patient has never experienced AF. Retrospective studies support the safety of this strategy and suggest a possible benefit in terms of early and late thromboembolic risk. It is also possible that routine LAA treatment will reduce the risk of stroke in those who develop new-onset postoperative AF. However, at this time, data are insufficient to support LAA management in patients with no history of AF.
The Left Atrial Appendage Exclusion for Prophylactic Stroke Reduction (LeAAPS) trial will clarify the role of LAA management in patients without a history of AF but with risk factors for AF and ischemic stroke. This trial will enroll up to 6500 patients undergoing cardiac surgery at 250 sites. The primary endpoint is occurrence of ischemic stroke or systemic embolism, with a minimum of 5-year follow-up period in all patients. If this trial proves positive, LAA management will likely become a component of nearly all cardiac surgical procedures.
How to Close the Left Atrial Appendage
By their very nature, surgeons are adept at the application of a needle holder with a needle and suture. With a single polypropylene suture, surgeons can achieve a secure and permanent aortic closure, coronary artery distal anastomosis, or insertion of a Dacron graft. One would surmise, therefore, that standard surgical techniques should suffice for suture closure of the LAA. Multiple studies refute this hypothesis. Suture closure of the LAA, whether with a pursestring suture or two-layered running suture, does not produce reliable secure and long-term exclusion of the appendage. Furthermore, incomplete closure of the LAA leaves patients at increased risk for thromboembolic events. Although it is possible that more involved suture techniques, including inversion of the appendage and incorporation of the appendage into the suture line, may result in more effective obliteration of the orifice, suture closure, in general, has proven disappointing.
Recognizing that suture closure of the LAA is problematic, some surgeons turned to staplers to either exclude or excise the LAA. Incorporation of pericardial strips helped to control staple line bleeding, but treatment was often incomplete because the procedure left a remnant cul-de-sac of LAA larger than 10 mm. In addition, noncutting staplers often allowed late recanalization of the LAA. Thus surgical staplers, which were generally designed for other purposes, do not present a reliable option for LAA management.
Excision of the appendage and oversewing its base is certainly effective but comes with an associated risk of bleeding. This is particularly troublesome in older individuals with fragile tissues. Although surgical excision was a mainstay of the original Cox Maze procedure, it has been supplanted by device-based closure.
Device-based closure with a commercially available clip designed specifically for the LAA is the safest and most reliable means of achieving complete and permanent LAA exclusion. The clip has a success rate that exceeds 95% but incorrect placement that is too far distal (i.e., not at the LAA base) represents failure.
Recanalization of a properly occluded appendage is virtually impossible. After clip placement, the LAA scars down and, over the course of months, essentially “disappears.” In addition, it becomes electrically “silent.” The clip comes in a variety of sizes and configurations, some of which are designed for minimally invasive thoracoscopic application. In patients with AF who are intolerant of anticoagulants and do not have anatomy suitable for an endovascular approach, epicardial thoracoscopic LAAO represents an excellent option. One would expect some growth in this surgical approach to the LAA in the future
Surgical Left Atrial Appendage Management: The Future
Among patients with AF undergoing concomitant surgery, the use of ablation, coupled with LAA exclusion, will continue to increase. Younger surgeons emerging from residency are well versed in the importance of AF management in their patients, and they will follow the guidelines that strongly endorse ablation with LAA management at the time of cardiac surgery. Even without the results of the LeAPPS trial, surgeons are increasingly embracing the concept of LAA management in patients without a history of AF but who are judged to be at high risk for developing AF or a stroke from atrial myopathy. This practice, too, will likely increase rapidly. The growth of surgical LAA management as a stand-alone procedure will be seen only in centers where surgeons and electrophysiologists collaborate closely. At this time, surgeons are thinking more and more about the LAA, and it is likely that LAA management will grow considerably in the surgical population.
References
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