Left Atrial Appendage Occlusion during Cardiac Surgery to Prevent Stroke (LAAOS III)

Take Home Message


Left atrial appendage is the most important site for thrombus formation inside the heart in patients with atrial fibrillation. Regardless performing the full Cox-maze procedure, the LAA must be removed or excluded in this special group of patients undergoing cardiac surgery for any cause. This reduce the risk for postoperative stroke.



La orejuela izquierda es el sitio más importante para la formación de trombos dentro del corazón en pacientes con fibrilación auricular. Independientemente de realizar el procedimiento completo de Cox-maze, la orejuela izquierda debe eliminarse o excluirse en este grupo especial de pacientes sometidos a cirugía cardíaca por cualquier causa. Esto reduce el riesgo de accidente cerebrovascular posoperatorio.



O apêndice atrial esquerdo é o local mais importante para a formação de trombos dentro do coração em pacientes com fibrilação atrial. Independentemente de realizar o procedimento Cox-maze completo, o apêndice atrial esquerdo deve ser removido ou excluído neste grupo especial de pacientes submetidos à cirurgia cardíaca por qualquer causa. Isso reduz o risco de AVC pós-operatório.


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Summary of the LAOS III

In this study the authors conducted a multicenter, randomized trial involving participants with atrial fibrillation (AF) and a CHA2DS2-VASc score of at least 2. Patients were randomized 1:1 to undergo or not undergo occlusion of the left atrial appendage (LAA) during cardiac surgery. A total of 2379 participants in the occlusion group and 2391 in the no-occlusion group were included and followed for 3.8 years. The primary outcome was the occurrence of ischemic stroke. Stroke was observed in 114 cases (4.8%) in the occlusion group and in 168 (7.0%) in the no-occlusion group (hazard ratio, 0.67; 95% CI, 0.53 to 0.85; P=0.001). They concluded that the risk of ischemic stroke or systemic embolism was lower with concomitant LAA occlusion.

My comment

By Ovidio A. García-Villarreal, MD

Cardiac Surgery. Consultant in Private Practice. Monterrey, México.

email: ovidiocardiotor@gmail.com


This study is the first RCT of this category in patients having Atrial Fibrillation (AF). It has been funded by the Canadian Institutes of Health Research and others (LAAOS III ClinicalTrials.gov number, NCT01561651). The authors have studied the effect to exclude the left atrial appendage (LAA) in patients having AF at the moment of undergoing cardiac surgery for any other reason. The authors studied 2379 patients in the group for LAA exclusion versus 2391 with no exclusion. The primary endpoint was any stroke or systemic embolic event. The mean follow-up was 3.8 years. 76.8% were under oral anticoagulation at this time. The result was 4.8% in the occlusion group and in 7.0% in the no-occlusion group (hazard ratio, 0.67; 95% confidence interval, 0.53 to 0.85; P=0.001) had any stroke or embolic event. The conclusion was that the risk of stroke or systemic embolism was lower with LAA occlusion [1].

Several important remarks are to be made here. LAA removal to reduce the risk for stroke has been suggested since the 1950s [2]. Blackshear and Odell were the first in figuring out a direct relationship between LAA and the thrombus formation inside the heart. Indeed, in an analysis of 1288 patients having non-valvular AF, 91% of all cardiac thrombus AF were located inside LAA. In stark contrast with the 57% in valvular-AF patients (p < 0.001) [3]. This has been the argument for LAA exclusion/occlusion over the years, and by different means, either percutaneous or surgical approach.

The efficacy of the LAA removal has also been studied by Johnson et al. [3] In a series of 437 patients, routine left atrial appendectomy was performed during open-heart surgery regardless the cardiac rhythm of the patients, with no problem related to surgical technique. In these terms, and considering AF becomes more frequent as the age of the patient advances, prophylactic LAA resection whenever the chest is open has been suggested as a method to prevent future strokes [3].

In this context, this trail by Whitlock et al. [1] is of paramount importance because is the first RCT in demonstrating the usefulness and efficacy of the LAA occlusion. Of note, based on the results of the Cox-maze procedure, in which the LAA is removed as a part of the surgical technique, we previously knew of the benefits of removing LAA in terms of stroke risk. As a matter of fact, in a series of 306 patients underwent Cox-maze procedure, the overall stroke rate was 0.7% in the perioperative period, 0.4% in the mean follow-up period of 4 years, or 0.1% per year [4]. As Dr. James L. Cox has stated out: “the ability of the maze procedure to decrease the risk of stroke associated with atrial fibrillation so dramatically is likely due to the restoring of sinus rhythm and atrial transport function in combination with surgical removal or obliteration of the left atrial appendage, where most thrombi associated with atrial fibrillation develop” [5]. As such, the stroke prevention has been proposed as an indication for the Cox-maze procedure [4].

García-Villarreal et al. demonstrated the importance of the LAA removal in patients with rheumatic mitral valve disease and long-standing persistent AF. In this series of 27 patients, only the LAA resection was applied together with the mitral valve procedure. In a follow-up of 18 months to 5 days, 96.3% of the cases were free of thromboembolic phenomena. Only one case (1/27, 3.7%) presented a transient ischemic attack with full recovery within the first three postoperative month. It is important to highlight that warfarin was administrated to all cases for the first three months. Afterwards, just an aspirin regime was utilized, with no cases (0%) of additional stroke after the third postoperative month. Therefore, the authors conclude that the LAA resection may eliminate the risk of stroke in patients with long-standing rheumatic mitral disease and long-standing persistent AF [6].

What about the recommendations in the guidelines for LAA exclusion in patients with AF? Whilst the 2017 STS Clinical Practice Guidelines for the surgical treatment of AF [7] give a recommendation Class IIA Level of Evidence C, for LAA exclusion in patients with AF undergoing cardiac surgery (regardless performing the full maze procedure), the 2020 ACC/AHA Guidelines for valvular heart disease indicate the same recommendation Class 2a, with a level of evidence as BN-R [8].

As a conclusion, the LAAOS III study by Richard Whitlock et al. [1], it takes on special importance as the first study of its kind as RCT demonstrating the reduction in the rate of postoperative stroke in patients with AF.

Nevertheless, we still have a long way to go in demonstrating whether or not the same LAA removal can be useful in reducing the stroke rate in patients in sinus rhythm who undergo cardiac surgery for any cause.

  1. Whitlock RP, Belley-Cote EP, Paparella D, et al. Left Atrial Appendage Occlusion during Cardiac Surgery to Prevent Stroke. N Eng J Med (2021). doi: 10.1056/NEJMoa2101897.
  2. Blackshear JL, Odell JA. Appendage obliteration to reduce stroke in cardiac surgical patients with atrial fibrillation. Ann Thorac Surg 1996;61(2):755-9. doi: 10.1016/0003-4975(95)00887-X.
  3. Johnson WD, Ganjoo AK, Stone CD, Srivyas RC, Howard M. The left atrial appendage: our most lethal human attachment! Surgical implications. Eur J Cardiothorac Surg. 2000 Jun;17(6):718-22. doi: 10.1016/s1010-7940(00)00419-x.
  4. Ad N, Cox JL. Stroke prevention as an indication for the Maze procedure in the treatment of atrial fibrillation. Semin Thorac Cardiovasc Surg 2000;12(1):56-62. doi: 10.1016/s1043-0679(00)70018-9.
  5. Cox JL, Ad N, Palazzo T. Impact of the maze procedure on the stroke rate in patients with atrial fibrillation. J Thorac Cardiovasc Surg 1999;118(5):833-40. doi: 10.1016/s0022-5223(99)70052-8.
  6. García-Villarreal OA, Heredia-Delgado JA. Left atrial appendage in rheumatic mitral valve disease: The main source of embolism in atrial fibrillation. Arch Cardiol Mex 2017;87(4):286-291. [Spanish]. doi: 10.1016/j.acmx.2016.11.007.
  7. Badhwar V, Rankin JS, Damiano RJ Jr, et al. The Society of Thoracic Surgeons 2017 Clinical Practice Guidelines for the Surgical Treatment of Atrial Fibrillation. Ann Thorac Surg 2017;103(1):329-341. doi: 10.1016/j.athoracsur.2016.10.076.
  8. Otto CM, Nishimura RA, Bonow RO, et al. 2020 ACC/AHA Guideline for the Management of Patients with Valvular Heart Disease: Executive Summary: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation. 2021;143(5):e35-e71. doi: 10.1161/CIR.0000000000000932.