〈Originals〉Relation between low take-off of the left atrial appendage and thromboembolic events in patients with atrial fibrillation : evaluation with multi-detector CT

Background:The left atrial appendage(LA-Ap)is one of the major sources of cardiac thrombus formation responsible for thromboembolism in patients with atrial fibrillation(AF). We hypothesized that the particular anatomical characteristics of the LA-Ap may facilitate thrombus formation. Methods:Seventy-four AF patients underwent transesophageal echocardiography(TEE)and multidetector CT(MDCT)examinations. These patients were divided into two groups, with and without systemic embolism(Emb)[Emb(+)group, 10 patients, male/female = 7/3; Emb(-)group, 64 patients, male/female = 51/13〕. To evaluate the location of the LA-Ap in relation to the left atrium(LA), we determined four distinctive points on MDCT images using two carefully defined orthogonal sections: the superior summit of the mitral annulus(point-A), the anterior and posterior sites of the LA-Ap orifice(point-B and C), and the posterior LA(point-D). Next, we evaluated the relation of the geometrical intervals(A-B, B-C, C-D)to the prior thromboembolism. Results:Using multivariate analysis, a shorter A-B interval was recognized as an independent factor positively associated with a history of thromboembolism. Conclusion:The position of the LA-Ap orifice may affect the hemodynamic state of the LA-Ap, and anterior deviation of the LA-Ap orifice(low take-off of the LA-Ap)may be a risk factor for thrombus formation in LA-Ap and systemic embolism.