The Morphology of Left Atrial Appendage Lobes: A Novel Characteristic Naming Scheme Derived through Three-Dimensional Cardiac Computed Tomography

Objectives: This study used cardiac CT to identify and name the different shapes of individual left atrial appendage (LAA) lobes and identified correlations between the size and shape of the LAA ostium and the volume of the LAA in a population of normal individuals. Background: The anatomy of the LAA appendage has become the subject of current research, because appendage occlusion devices have emerged for patients with atrial fibrillation. The development of cardiac computed tomography (CT) allows researchers to identify and observe cardiac anatomy, including various shapes of the LAA lobes. Methods: This study was a retrospective review of 102 consecutive patients from March 2009 to November 2010 who underwent cardiac CT using the GE 64-slice Light Speed VCT CT scanner. For each patient, the LAA ostium was measured, and the shape of the ostium was observed and described. After the LAAs were reconstructed 3-dimensionally, each LAA was categorized by its shape and number of lobes. Results: No significant difference was observed between the average LAA volume between males and females. LAA appendages with circular ostium (n = 61) were observed to have a larger mean volume than those with elliptical ostium (n = 39). Predictors of LAA volume were identified. The most common number of lobes was 2 (n = 61), followed by 1 (n = 27), 3 (n = 10), and 4 (n = 2). Eight unique LAA morphologies were identified and a name was assigned to each morphology. Based on the shape and number of lobes observed, the most common LAA lobe shape was hook (n = 55), followed by wing, arrowhead, flame, double wing, finger, sea horse, double hook, knob, spiral, and double knob. Conclusion: This study used Corresponding author. D. S. Beutler et al. 18 3D cardiac CT to identify and name the morphology of individual LAA lobes as one of eight different types. The Beutler-Loli naming system formulates a basis to improve understanding of the complex structure of LAA anatomy and to facilitate a system for researchers and clinicians to communicate more precisely about the LAA.