Abstract 4373175: Complete Left Atrial Appendage Membrane Mimicking Congenital Absence on TEE

Background: Left atrial appendage (LAA) membranes and congenital absence of LAA are extremely rare anatomical variants seen on transesophageal echocardiography (TEE). There are very few cases reported of LAA membrane and congenital absence of LAA in the literature. We present two cases with a LAA membrane, with the second case mimicking congenital LAA absence. Description of Case: Case 1: A 57-year-old male with persistent AF and dilated cardiomyopathy underwent TEE prior to pulmonary vein isolation. TEE revealed a fenestrated membrane at the ostium of the LAA, causing partial obstruction evidenced by a well-defined jet into the left atrium. The fenestrated membrane was well demonstrated by advancing intra-cardiac echocardiogram (ICE) probe into the left atrium (Figure 1). Case 2: A 60-year-old female with paroxysmal AF and hypertension, presented with non-ST-elevation myocardial infarction and was found to have triple vessel disease. She was planned for coronary artery bypass grafting (CABG), MAZE procedure, and LAA excision. Intraoperative TEE did not visualize any LAA, suggesting congenital absence of LAA. However, a LAA was seen intra-op, which was empty and collapsed due to the presence of complete membrane at the ostium without any fenestrations (Figure 2). Discussion: These cases illustrate that LAA membranes can rarely be present, which can be partial, fenestrated or complete. Presence of a complete membrane leads to a collapsed LAA, which can not be visualized on TEE mimicking congenital absence of LAA.