From diagnosis to disappearance: a case report on managing atrial septal thrombus with anticoagulation.

Background: The occurrence of atrial septal impending paradoxical embolism in a patent foramen ovale is a rare clinical phenomenon. In a patient with pulmonary artery embolism, transthoracic echocardiography (TTE) revealed a trans-atrial septal impending paradoxical embolism. This prompted us to consider: What is the nature of this cardiac lesion, and why is it embedded in the patent foramen ovale?

Case summary: A 37-year-old man presented with chest tightness and shortness of breath for 1 week, acutely worsening in the last day before admission. Enhanced computed tomography of the pulmonary artery indicated extensive pulmonary embolism, while TTE showed a large earthworm-shaped mass (∼4.2 cm × 1.4 cm) in the atrial septal fossa ovalis, oscillating slightly with the cardiac cycle. Initially, it was unclear whether the mass was a thrombus or a myxoma. However, after 12 days of anticoagulation, the mass disappeared, suggesting it was a thrombus. The patient underwent percutaneous pulmonary thrombectomy of both arteries, resulting in symptom improvement and stabilized vital signs. Given the patient's young age, such a massive embolic event was unusual. Genetic testing for thrombophilia revealed a PROC gene mutation, clarifying the aetiology.

Discussion: Pulmonary embolism-induced pulmonary arterial hypertension increased right-to-left shunting through the atrial septal patent foramen ovale, contributing to impending paradoxical embolism development at this site. Thrombophilia might be a key risk factor for this venous thrombotic event.