Giant left atrial appendage aneurysm: A case of mistaken identity.

Left atrial appendage (LAA) aneurysm is a rare condition that can be congenital or acquired. Most cases are discovered incidentally. However, the most frequent clinical presentations include supraventricular tachycardias and systemic embolization. Most cases in the literature were treated by resection of the LAA, and it has been recommended to perform LAA resection even in asymptomatic patients in order to prevent thromboembolic events. Here, we describe the safe, conservative management of a patient who was initially felt to have congenital partial absence of the left pericardium but at surgery the diagnosis of LAA aneurysm was established. <Learning objective: LAA aneurysm is a rare condition which has typically been managed with prompt surgical excision due to the perceived high risk of thromboembolic events. Our case demonstrates that LAA aneurysm and its associated arrhythmias can be treated medically with AV-nodal blockade and oral anticoagulation in the asymptomatic patient. Conservative management of asymptomatic patients with a LAA aneurysm with close monitoring of LAA size may allow for a delay or possible avoidance of surgery.>.