(a), (b) Images demonstrating significant interindividual variation in left atrial appendage (LAA) morphology (A: chicken wing; B: windsock). The tip of the LAA can be in a variety of positions, lying over the pulmonary trunk (PT) and the left anterior descending (LAD) coronary artery (a) or even directed medially towards the back of the aorta (b). (c) Endocardial visualization of the left posterolateral wall showing a prominent left lateral ridge (LLR) and extra pectinate muscle trabeculations (arrows) extending inferiorly from the appendage to the vestibule of the mitral valve. Transillumination in this specimen shows the atrial wall becoming exceptionally thin. (d) Endoscopic CT angiography view of the left posterolateral wall shows the relationship of the left superior pulmonary vein (LSPV) and the ostium of the LAA. In this example, both are located at the same level. The LLR is relatively thin. (e) Axial CT view at the left of the LAA shows a single lobe LAA and a thin LLR between the LAA and the left superior pulmonary vein (LS). The red arrow shows the left sinoatrial node artery arising from the left circumflex artery. Ao = aorta, LI = left inferior pulmonary vein, LS = left superior pulmonary vein, MV = mitral valve, and LCPV = left common pulmonary vein.
