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Can J Cardiol. 2013 Nov;29(11):1443-7. doi: 10.1016/j.cjca.2013.06.015. Epub 2013 Sep 20.

Left Atrial Appendage Occlusion Study II (LAAOS II).

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Population Health Research Institute, Hamilton Health Sciences/McMaster University, Hamilton, Ontario, Canada. Electronic address:



Occlusion of the left atrial appendage (LAA) is a potential alternative to anticoagulation for patients with atrial fibrillation (AF); however, evidence of its safety and efficacy is lacking. The Left Atrial Appendage Occlusion Study II (LAAOS II) explored the feasibility of a definitive trial of LAA occlusion for stroke prevention in AF.


A cross-sectional study of 1889 consecutive patients undergoing cardiac surgery was performed to determine the prevalence of AF and risk factors for stroke. We also randomized 51 patients with AF and increased stroke risk to LAA occlusion (n = 26) or no occlusion and oral anticoagulation (n = 25) to assess the rate of recruitment and the safety of LAA amputation.


In the cross-sectional study, 204 patients (10.8%) had AF and 98 (5.2%) met trial eligibility. Fifty-one patients were recruited into the trial at a rate of 1.6 patients per centre per month. No patient with occlusion had significant bleeding at the LAA site. At 1 year, 4 patients (15.4%) in the occlusion arm and 5 patients (20.0%) in the no-occlusion arm experienced death, myocardial infarction (MI), stroke, noncerebral systemic emboli, or major bleeding (relative risk [RR], 0.71; 95% confidence interval [CI], 0.19-2.66; P = 0.61). The predominant component of the composite was stroke, with 1 in the occlusion arm and 3 in the no-occlusion arm.


LAA occlusion can be safely performed at the time of cardiac surgery. A large trial to evaluate the clinical efficacy of LAA occlusion in patients undergoing cardiac surgery is possible in motivated centres with some modifications to the design of LAAOS II.

[Indexed for MEDLINE]

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