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Transposition of the Great Arteries — RACP Paediatrics MCQ

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ModerateCardiologyTransposition of the Great ArteriesRACP Paediatrics

A 3-month-old infant is found to have a SpO2 of 75% on routine pulse oximetry screening. There is no murmur. The infant appears cyanosed but not in distress. A chest X-ray shows an egg-on-string cardiac silhouette with increased pulmonary vascular markings. What is the most likely diagnosis?

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Correct answer: A — Transposition of the great arteries

The 'egg-on-string' or 'egg-on-side' appearance on CXR, combined with cyanosis and increased pulmonary vascular markings, is characteristic of transposition of the great arteries (TGA). In TGA the aorta arises from the right ventricle and the pulmonary artery from the left ventricle, creating parallel circulations. Most cases present in the newborn period.

Reference: RCH Melbourne – 2024 – Clinical Practice Guidelines: Cyanotic Congenital Heart Disease