Right Atrial Thrombus Mimicking a Myxoma: Synergism of Hormonal Contraceptives and Antiphospholipid Antibodies

Cardiac thrombus, the most common intracardiac mass, is typically seen in the left side of the heart in the presence of atrial fibrillation, mitral stenosis, or impaired global wall motion. Right atrial thrombus, which is rarer, is usually associated with central venous catheter placement or pulmonary embolism. We present the case of a 24-year-old woman with a history of mitral valve prolapse who presented with fatigue and palpitations. Echocardiograms and cardiac magnetic resonance images revealed a right atrial mass compatible with a myxoma. However, after surgical excision of this and a second mass discovered intraoperatively, pathologic evaluation confirmed organized thrombus rather than myxoma. The patient's only risk factor was her use of oral contraceptive pills. Test results for hypercoagulable disorders revealed the presence of antiphosphatidylserine, an uncommon antiphospholipid antibody. The patient stopped taking the contraceptive. This case suggests the need to examine further the role of antiphosphatidylserine antibodies in the diagnosis of antiphospholipid syndrome. (Tex Heart Inst J 2022;49(4):e207455)