Post-cardioversion atrial stunning - Not to be forgotten.

We present a case of a 60-year-old male who was found to be in atrial fibrillation during routine evaluation. Anticoagulation was initiated for 36 h and he was referred for TEE-guided electrical cardioversion. There was no thrombus identified in the left atrial appendage, however, the appendage was large and had a tongue-like accessory lobe along with spontaneous contrast in the left atrium and its appendage. TEE probe was not withdrawn, patient underwent successful cardioversion with 200 joules and developed a marked increase in left atrial and left atrial appendage spontaneous contrast along with the development of tear drop shaped thrombus in the left atrial appendage immediately after cardioversion, which rapidly became more dense. There was an associated marked decrease in appendage velocities. Patient was hospitalized to initiate low molecular weight heparin. This case highlights the need for vigilance in patients with an unknown duration of atrial fibrillation, who have received a short duration of anticoagulant therapy and who have adverse appendage anatomy as thrombus may develop immediately after cardioversion despite anticoagulation.