Giant thrombus formation immediately after mitral valvuloplasty

Patients with atrial fibrillation (AF) are at risk of cardioembolism.^1,2) Atrial thrombus formation associated with AF typically occurs in the left atrial appendage (LAA);³) therefore, transesophageal echocardiography (TEE) is important for detection of such a thrombus and measurement of LAA flow velocity.^4,5) LAA closure is routinely performed during mitral valve surgery in patients with AF to prevent cardiogenic stroke.⁶) We report the case of a 65-year-old woman with severe mitral regurgitation (MR) and AF in whom a giant thrombus formed almost immediately after mitral and tricuspid valvuloplasty and concurrent LAA resection. No atrial thrombus or spontaneous echo contrast (SEC) was detected by TEE before the surgery. However, a giant intramural thrombus was detected in the left atrium 7 days after surgery. It was thought that the atrial dysfunction as well as the change in morphology of the left atrium resulting from the severe MR complicated by AF and congestive heart failure produced a thrombotic substrate. This case suggests that careful surveillance for thrombus formation and careful maintenance of anticoagulation therapy are needed throughout the perioperative period even if no SEC or thrombus is detected before surgery.