A 78-year-old man with a history of permanent atrial fibrillation and a mitral valve replacement (a 29 mm St Jude mechanical valve) for rheumatic disease 10 years before, was admitted by an acute cardioembolic coronary syndrome without ST elevation. Although he was treated with acenocoumarol his target index normalised ratio was not achieved. The transthoracic echocardiography showed that the mitral valve area measured by the pressure half time method was 0.9 cm2. The transvalvular gradient through the prosthesis was 10 mmHg. Because of the poor acoustic window, a transesophageal echocardiography was performed. The left atrium was completely occupied by a giant non-homogeneous, irregularly-surfaced mass (Fig. 1) which was obstructing the disc motion, mimicking severe mitral prosthetic stenosis (video 1). He was scheduled for cardiac surgery. A huge thrombus was removed but unfortunately he died during the surgery.

Fig. 1
figure 1

Thrombus in left atrium. Transesophageal echocardiography showing a huge thrombus (asterisk) occupying almost the entire left atrium. LA Left atrium, LV left ventricle

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