A newborn has cyanosis and a single second heart sound. The chest radiograph shows a narrow superior mediastinum with a heart described as 'egg on a string'. Which lesion does this classic appearance represent?
- A Ebstein anomaly
- B Truncus arteriosus
- C Transposition of the great arteries ✓
- D Hypoplastic left heart syndrome
Correct answer: C. Transposition of the great arteries
Explanation
In d-transposition of the great arteries, the aorta lies directly anterior to the pulmonary artery, so the vascular pedicle appears narrow on frontal projection, giving the 'egg on a string' contour. Cyanosis from day one with this silhouette is diagnostic. Truncus arteriosus instead gives a wide mediastinum with a large pedicle, which kills that distractor.
Reference: Park's Pediatric Cardiology for Practitioners, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.