701 Left Atrial Appendage Congenital Absence and Atrial Fibrillation

Abstract

Introduction Left atrial appendage (LAA) is a finger-like muscular extension of the left atrium (LA). It acts as blood reservoir, modulates LA pressure and elicits adaptive responses to stress. Several LAA shapes and variants have been described. We report a case of congenital absence of LAA diagnosed by transesophageal echocardiography (TEE) and confirmed by computed tomography (CT). Case report A 55-year-old male patient with history of hypertension was admitted to our hospital for an episode of atrial fibrillation (AF). TEE was performed and showed normal LA volume, absence of thrombi and spontaneous echo contrast in the LA, but, despite acquiring three-dimensional (3D) en-face views, we were unable to identify LAA. Congenital absence of LAA was suspected and multidetector cardiac CT confirmed the abnormality. Discussion Congenital absence of LAA is an extremely rare condition: only eighteen cases were described on a review of the literature published in 2020. Associations with other congenital abnormalities or with atrial fibrillation have been reported, but a causal relationship cannot be established. Multiple imaging modalities can be used to define the anatomy and function of LAA, to detect or rule out in situ thrombosis and to guide catheter-based therapies, but the most widely used technique is TEE. Among intracardiac thrombi in patients with non-valvular atrial fibrillation, more than 90% are identified in the LAA, meaning that the remaining 10% may develop in other sites of the LA. The congenital absence of LAA could be considered similar to LAA percutaneous occlusion or surgical exclusion; because of the few published randomized controlled trials, the current ESC guidelines on atrial fibrillation are unclear about the true thrombotic risk in these cases. Since LAA percutaneous occlusion is actually indicated only in cases of contraindications for long-term anticoagulant treatment, in our opinion in patients with non-valvular AF, LAA congenital absence, high stroke risk and low bleeding risk, anticoagulant therapy should be considered. Conclusion Congenital absence of LAA is an extremely rare condition and its pathophysiological role, especially with regard to antithrombotic therapy in patients with AF, is still not well defined.