Unusual left atrial mass: inverted left atrial appendage caused by massive pericardial effusion.

Left atrial appendage inversion is a very rare cause of left atrial mass that usually occur after cardiac surgery. Its echocardiographic appearance often misleads clinicians to the diagnosis of thrombus or cardiac neoplasms. Unfortunately, misdiagnosed patients often undergo unnecessary anticoagulation or surgical treatment. We are presenting a case of left atrial appendage inversion caused by massive pericardial effusion in a patient with no previous history of cardiac surgery together with demonstrative images of transesophageal echocardiography and magnetic resonance imaging.