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Egg-on-a-string sign (heart)

Last revised by Assoc Prof Craig Hacking on 05 May 2020

Egg-on-a-string sign, also referred to as egg on its side, refers to the cardiomediastinal silhouette seen in transposition of the great arteries (TGA).

The heart appears globular due to an abnormal convexity of the right atrial border and left atrial enlargement and therefore appears like an egg.

The superior mediastinum appears narrow due to stress-induced thymic atrophy and hyperinflated lungs which give the picture of an egg suspended by a string on a chest radiograph, hence the name egg-on-a-string.

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