An Uncommon Cause of Massive Pulmonary Embolus
A 21-year-old female patient with a medical history of asthma and multiple presentations to the emergency department with chest pain in the several months prior presented to the emergency department with constant right shoulder pain of 2 days duration. On arrival, she had a blood pressure of 138/71 mmHg, a heart rate of 125 bpm, a respiratory rate of 14/min, a temperature of 100.2°F, and a pulse oximetry of 97% on room air. Except for the patient's tachycardia, both heart and lung examination were unremarkable. During diagnostic workup in the emergency department, thoracic radiography was normal, and an electrocardiogram showed sinus tachycardia. A transthoracic echocardiogram was recommended to evaluate for right heart strain, and it demonstrated a 3 cm mass in the right atrium, mild tricuspid regurgitation, and pulmonary pressures of 50-55 mmHg. A transesophageal echocardiogram (TEE) was then performed, and it showed a 4 x 2.7 cm pedunculated independently mobile mass attached to the high interatrial septum. The mass was heterogeneous with a serpiginous hyperdensity attached to it. The mass did not involve the tricuspid valve annulus or the valve itself. On review of a computed tomography (CT) scan obtained 3 months earlier when the patient presented with similar symptoms, CT then showed a very small mass, indicating that the mass grew to over 3 times its original size in less than 3 months.
What is the most likely diagnosis?