Clinical Research Left Atrial Appendage Occlusion Study II (LAAOS II)

Background: 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 ad e finitive trial of LAA occlusion for stroke prevention in AF. Methods: A cross-sectional study of 1889 consecutive patients undergoing cardiac surgery was performed to determine the preva- lence of AF and risk factors for stroke. We also randomized 51 patients with AF and increased stroke risk to LAA occlusion (n ¼ 26) or no RESUME Introduction : L'occlusion de l'appendice auriculaire gauche (AAG) est une solution de rechange potentielle a l'anticoagulation chez les patients ayant une fibrillation auriculaire (FA). Cependant, il manque de donnees scientifiques attestant son innocuite et son efficacite. L'etude LAAOS II (Left Atrial Appendage Occlusion Study II) a explor el a faisabilit ed 'un essai concluant sur l'occlusion de l'AAG dans la prevention de l'accident vasculaire cerebral (AVC) lors de FA. Methodes : Une etude transversale comprenant 1889 patients con- secutifs ayant subi une chirurgie cardiaque a et er ealisee pour Oral anticoagulant (OAC) therapy is effective and is the standard for stroke prevention in atrial fibrillation (AF). However, OAC has well-recognized limitations that result in its underuse, being administered to as few as 25% of patients with AF and only 70% of patients who are felt to be "ideal" candidates for warfarin therapy. 1-7 Based on the limitations of OAC therapy, physicians and patients continue to seek an effective, low-risk therapy that could eliminate the need for oral anticoagulants and their associated risks. Most strokes in AF result from embolisms and are thought to originate from the thrombi in the left atrial appendage (LAA). 8 In a post hoc exploratory analysis of the Stroke Prevention in Atrial Fibrillation III (SPAF III) trials, 68% of the classifiable strokes were judged to result from embolism. The proposed site of origin of embolic strokes from the LAA in patients with AF is based on echocardiographic evidence. In 1 study of 233 patients with AF who were not taking warfarin, 34 patients (15%) had left atrial thrombus, all of which (except 1) were located in the LAA. In another study of 272 patients with AF who did not have rheumatism, the incidence of thrombi in the LAA was 8%. Based on a review of these and other studies, it was concluded that at least 90% of left atrial thrombi are found in the LAA. 9 It is therefore reasonable to propose that occlusion of the LAA would greatly reduce the risk of stroke in patients with AF. 10 To date, no conclusive evidence exists that LAA exclusion is effective in preventing stroke in patients with AF. Patients undergoing open heart surgery are an ideal population to test the hypothesis because the LAA can be readily removed at the time of surgery, with minimal additional cost and presumably minimal additional risk.