A 68-year-old woman was admitted for major dyspnoea. A transoesophageal echocardiogram was performed after the occurrence of acute circulatory shock. During the examination, the patient was under mechanical ventilation. We found a thrombus that had almost occluded the right pulmonary artery and which was later confirmed by selective angiography. Despite treatment, the patient died 2 days later; autopsy confirmed the thrombus in the right pulmonary artery.