Congenital Absence of left atrial appendage: A case report

Introduction The left atrial appendage (LAA) is one of the most common sites for thrombus formation in patients with atrial fibrillation (AF). Congenital absence of left atrial appendage (LAA) is an extremely rare cardiac condition and it is likely a congenital anatomical variation. We want to report a rare case of congenital absence of LAA diagnosed by transesophageal echocardiography evaluations before AF ablation procedure. Methods A 75-year-old man presented with a history of hypertension and drug resistant paroxysmal AF/ atypical flutter was admitted to the Cath lab for arrhythmia ablation. As part of the pre-procedure evaluation for an elective ablation, the patient underwent transesophageal echocardiography (TEE) to exclude LAA thrombus. The TEE imaging at multiple acquisition angles, the LAA could not be visualized and an absence of the LAA was suspected and confirmed by cardiac computed tomography (CT), which included 3D reconstruction. Both modalities showed no apparent intracardiac thrombus, and then he followed in having catheter ablation. Prior to pulmonary vein (PV) isolation, LA electroanatomic reconstruction with HDGrid catheter and Ensite X system (Abbot Medical, USA) was performed and the LAA was also not visualized around the usual root location of the LAA. The catheter ablation was finished successfully, and he has continued to do well with sinus rhythm. Results Within the first 4 weeks of embryonic life, the LAA develops from the primordial LA, which is formed through the adsorption of the primordial pulmonary veins. The LAA shows a finger- like structure arising from the anterolateral site of the main LA. The role of the LAA has not been elucidated sufficiently, but it has been suggested that the LAA assists LA contractile function and prevents an increase in LA pressure because of the LAA being more flexible than the main LA. Likewise, the LAA has considerable clinical importance as the most common site of thrombus formation leading to thromboembolic events. Such a clot may embolize peripherally, resulting in ischemic insult to the brain, kidneys and other organs supplied by the systemic circulation. It is therefore imperative to ensure the absence of any LAA thrombus before a patient with AF can be cleared for cardioversion or ablation. In most cases, such abnormal conditions are found incidentally during TEE or CT prior to catheter ablation for atrial fibrillation. A few cases were accompanied by persistent left superior vena cava as another congenital cardiac association documented by CT angiography. Discussion Congenital absence of LAA is an extremely rare cardiac anomaly and only a few cases have been reported so far. We have reported this case found by pre-procedure evaluation for an elective ablation. This entity was confirmed by 3D CT. Most of the previous cases similar to ours described a truly absent LAA, implying an influence on decision-making for anticoagulation treatment and LAA interventions. Multimodality imaging may be necessary to do a differential diagnosis.