An AP chest radiograph of a newborn reveals an egg-shaped cardiac silhouette. This would be consistent with

• A. Total anomalous pulmonary venous return
• B. Tetralogy of Fallot
• C. Transposition of the great vessels
• D. Ventricular septal defect

Answer: (C)

An egg-shaped, or globular, cardiac silhouette with a relatively narrow mediastinum in a newborn is a classic clue for transposition of the great arteries. In this condition, the aorta arises from the right ventricle and the pulmonary artery from the left ventricle, which tends to produce a compact, rounded heart size against a narrow mediastinum on an AP view—the so‑called egg-on-a-string appearance. This imaging pattern helps distinguish it from other neonatal heart diseases: a boot-shaped heart points toward Tetralogy of Fallot due to right ventricular hypertrophy; total anomalous pulmonary venous return often shows a snowman/figure‑of‑eight pattern depending on the drainage type; a simple ventricular septal defect may not produce a distinct silhouette. So the described egg-shaped heart best fits transposition of the great arteries.