Atrial tachycardia in congenital left atrial appendage aneurysm: three-dimensional computed tomography imaging with electro-anatomical mapping

A 29-year-old woman was admitted for the evaluation of atrial tachycardia (AT) associated with palpitation during exercise. She had been diagnosed with a left atrial appendage (LAA) aneurysm at the age of 19 years. She was followed by echocardiography annually because she was asymptomatic, and evidence of thrombus formation and/or atrial tachyarrhythmia was not found. She developed AT 2 months before admission. The 12-lead electrocardiogram (ECG) revealed AT with a 2:1 ventricular response (Panel A). The P-wave morphology indicated the origin of AT as the superior portion of the left atrium. The chest X-ray showed an abnormal upper left heart border. The transthoracic echocardiogram demonstrated a very large LAA aneurysm. Her left ventricular function and cardiac valves were normal. Both transesophageal echocardiography and cardiac 64-slice multi-detector computed tomography (CT) showed no evidence of thrombus formation in the aneurysm. The derived LAA volume was 74 mL by CT and 75 mL by three-dimensional transesophageal echocardiography. In the electrophysiological study, the activation sequence indicated an AT cycle length of 282 ms, which originated from the left atrium. Three-dimensional electro-anatomical mapping fusion with CT imaging of the left atrium (CARTO Merge, Biosense Webster, Inc.) was performed. The earliest activation site during AT was mapped at the anterior site at the roof of the LAA aneurysm, 66 mm from the neck (Panel B, Supplementary Data). An LAA aneurysmectomy was performed via left thoracotomy (Panel C). There was no thrombus formation within the aneurysm. Histological findings demonstrated marked thinning of the LAA wall with increased fibrous tissue consistent with an aneurysm (Panel D). The patient has remained asymptomatic and in sinus rhythm without medication for 8 months postoperatively.