A 55-year-old male patient presented with retrosternal chest pain with ST elevation in anterolateral leads and atrial fibrillation (AF) on electrocardiogram. Transthoracic echocardiography (TTE) revealed hypokinetic anterior wall with left ventricular ejection fraction 48% and no evidence of clot in cardiac chambers. Coronary angiography showed triple vessel disease and patient was scheduled for off pump coronary artery bypass grafting (CABG). Transesophageal echocardiography (TEE) during pre-bypass period revealed a freely mobile clot in left atrial appendage [LAA; [Figure 1], [Video 1] . After discussing TEE finding with the operating surgeon, it was decided to proceed for CABG on cardiopulmonary bypass (CPB) and three grafts were anastomosed to diseased coronary vessels, and the LAA clot was removed. After separation from CPB, 2D-TEE showed clot like shadow in LAA [Figure 2], [Video 2] . While speculating whether it was an inadequate removal of LAA clot or new clot formation, the operating surgeon inspected outer surface of the LAA wall and found a part of the LAA inverted. The inverted left atrial wall tissue spontaneously everted with the improved cardiac filling and the image disappeared on TEE imaging.
Figure 1: Midesophageal two chamber view shows clot in left atrial appendage (pre surgery)
LA clot is commonly observed in patients with AF. Such finding can be missed during TTE examination as would have occurred in this case. It is advisable to perform TEE examination pre-operatively in patients with AF to rule out LAA clot so that surgery can be planned accordingly. Inversion of the LAA tissue after cardiac surgery mimicking a LA mass is rare. It is mostly recognized during weaning from CPB while the heart is still empty. , The LAA generally everts spontaneously once the heart is filled.  Apart from causing confusion in the diagnosis, it can cause mitral valve obstruction and impaired ventricular filling. , Inability to identify such a mass as an inverted LAA can result in unnecessary surgical intervention, unnecessary return to CPB and additional ischemic time. , The key to recognize inverted LAA is being aware of its existence and considering its possibility in the differential diagnosis of a newly appearing LA mass.  3D-echocardiography can help in differentiating the inverted LAA and clot. Failure of an appendage to evert upon LA filling can be corrected by Valsalva maneuver, digital manipulation, pulling by forceps; occasionally, LA appendage ligation might be required.