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A 20 year old male patient was operated on for atrial septal defect (ASD) at our hospital. No complications were evident one month postoperatively, and clinical and echocardiographic findings were normal. However, six months later transthoracic echocardiography showed a large, highly mobile 2.4 × 2.3 cm right atrial mass (middle panel, centre column), although no mass was seen in the cardiac chamber at the preoperative transthoracic echocardiogram (upper panel, centre column) in apical four chamber view. Transoesophageal echocardiography revealed a large, mobile, mushroom shaped mass attached by a long thin stalk to the right atrial free wall near the entrance of the inferior vena cava (upper panel, right column) eight months postoperatively. The mass in the right atrium was not detected by transoesophageal echocardiography preoperatively (lower panel, centre column). The similar characteristics of the mass were also determined by subcostal two dimensional echocardiogram (middle panel, right column). Because of concern about the risk of thromboembolism, open heart surgery was performed. The mass was completely removed (lower panel, right column). Histologic studies showed that the mass was composed entirely of thrombotic material with focal regions of calcification. Laboratory data, venous ultrasonography, and pulmonary ventilation perfusion scintigraphy of the patient were normal.
Thrombus formation in the right atrium may occur as a result of endocardial damage following closure of an ASD. To our knowledge, this is the first documented case of a right atrial thrombus following closure of an ASD.