Analysis of the left atrial appendage by magnetic resonance angiography in patients with atrial fibrillation

BACKGROUND Recent interest has focused on the left atrial appendage (LAA) in the setting of atrial fibrillation as a potential source of thromboembolism and stroke, which may be amenable to permanent occlusion by a variety of investigational catheter-delivered devices. Precise anatomic characterization of the LAA is necessary to determine the suitability of a patient for device placement and for device selection and sizing. OBJECTIVES The purpose of this study was to perform detailed three-dimensional characterization of LAA size and geometry by magnetic resonance angiography. METHODS Fifty patients with chronic atrial fibrillation undergoing cardiac magnetic resonance angiography in preparation for catheter ablation of atrial fibrillation were analyzed for LAA volume, neck size, depth, and overall geometry. RESULTS The average LAA volume was 17.3 +/- 6.7 mL, with a depth of 26.6 +/- 4.9 mm and a "neck" diameter of 20.0 +/- 5.3 mm X 14.1 +/- 4.7 mm. The average number of LAA lobes was 1.4 +/- 0.7 (range 1-4). Substantial interpatient variability was present in the relative dimensions and morphology of the LAA. There was a significant correlation between left atrial size and LAA neck dimensions. CONCLUSION There is significant heterogeneity in LAA size and dimensions among patients with atrial fibrillation. Device occlusion of the LAA may require devices that are available in multiple sizes/shapes or that can adapt to this heterogeneity.