Atrial appendage aneurysm, which may be due pectinate muscles increased atrial pressure, is a localized or diffuse dilatation of the atrial appendage. 1 Patients are usually asymptomatic, while those with symptoms may manifest exertional dyspnea, atrial tachycardia, and/or thromboembolism. 1 Surgery is the recommended treatment to avoid these severe complications. 2