The posterior aspect of the left atrial appendage (LAA) lies close to the left superior pulmonary vein (LSPV), the left inferior pulmonary vein (LIPV), and ligament of Marshall (LOM). (A, B) The superior aspect is related to the pulmonary artery (PA) and left PA. The left circumflex artery (LCX), the great cardiac vein (GCV), and the left ventricle (LV) lie in close proximity to the inferior aspect. The left phrenic nerve (LPN) crosses posterolaterally. On the endocardial aspect (C), the left lateral ridge (LLL) at the corresponding area of the LOM separates the LAA ostium from the LSPV. There are several pits or diverticula around the indistinct border of the ostium (*). Also see Online Video 1. LAA = left atrial appendage.