Lung Perfusion Scintigraphy Reveals a Duplicated Superior Vena Cava With a Right-to-Left Shunt: A Rare Vascular Variant.

Lung perfusion scintigraphy is a common nuclear medicine exam performed for the evaluation of pulmonary emboli, often in the emergency setting. There can be confusion when a radiotracer is located outside of the normal physiologic distribution. This can occur due to improper radionuclide tagging or may be due to anatomic variations. We present a case where a patient presented with bilateral lower extremity deep vein thrombosis and a nuclear medicine lung perfusion scintigraphy showing a complete right-to-left shunt related to a rare anatomical variant of a duplicated superior vena cava (SVC) with the right SVC draining directly into the systemic circulation via the left atrium.