Right Atrial Anomalous Muscle Bundle Presenting with Acute Superior Vena Cava Syndrome and Pulmonary Embolism:...

An anomalous muscle bundle (AMB) crossing the right atrial cavity represents a pathologic finding with unproved clinical significance. This congenital anomaly may be difficult to recognize via echocardiography and could be confused with other intracavitary lesions.

We report the case of a 53-year-old woman presented to the cardiovascular service with acute superior vena cava (SVC) syndrome and submassive pulmonary embolism.

The patient underwent venography, confirming SVC stenosis. A ventilation/perfusion lung scan showed 2 sizable perfusion defects because of pulmonary embolism. Magnetic resonance imaging and echocardiography imaging demonstrated a right atrium (RA) mass. Surgery was then carried out using standard cardiopulmonary bypass; the right atrial muscle bundle was excised, and SVC reconstruction was performed. The patient was discharged uneventfully and remains symptom-free at 2-year follow-up.

In cases of nonmalignant pathology of SVC syndrome, appropriate studies should be conducted to exclude potential congenital abnormalities such as this AMB in the RA. Open-heart surgery is a viable treatment option in select cases.