On a chest X-ray of a 6-week-old infant, there is a 'snowman' or figure-of-eight cardiac silhouette. This is MOST characteristic of which congenital cardiac anomaly?

• A Transposition of great arteries
• B Truncus arteriosus
• C Total anomalous pulmonary venous connection (TAPVC) supracardiac type ✓
• D Tricuspid atresia

Explanation

The 'snowman' or figure-of-eight cardiac silhouette on CXR is pathognomonic of supracardiac TAPVC (Type I), where all pulmonary veins drain into a vertical vein on the left, which empties into the left innominate vein and then the right superior vena cava, creating a dilated superior mediastinal shadow that combined with the cardiac shadow forms the snowman shape. TGA shows an egg-shaped heart with narrow superior mediastinum; truncus arteriosus shows a right aortic arch in 30%; tricuspid atresia shows decreased pulmonary vascularity.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.