Question

The 'Egg on side' (egg lying on its side) appearance on a chest radiograph is seen in:

• A. Tricuspid atresia
• B. Tetralogy of Fallot
• C. Total anomalous pulmonary venous connection (TAPVC)
• D. Transposition of the great arteries

Hint:

Think of the great vessels stacked front to back, narrowing the mediastinal pedicle.

Answer 1

The Correct Option is D

Each cyanotic congenital heart lesion has a signature cardiac silhouette that examiners love to test. To answer this, match the descriptive sign to the lesion.

The phrase 'egg on side' (also called 'egg on a string') describes an oval cardiac shadow sitting on a thin stalk. The thin stalk is the narrow superior mediastinal vascular pedicle. This narrowing happens because in transposition of the great arteries the aorta sits straight in front of the pulmonary trunk, so on a front-facing film the two big vessels stack rather than spread out. Add an involuted thymus and a rounded, mildly enlarged heart, and the result is an egg lying on its side.

Run through the distractors. Tetralogy of Fallot is the 'boot-shaped' heart. Supracardiac TAPVC is the 'snowman' / 'figure of 8'. Tricuspid atresia tends to give a normal or small heart with oligemic lung fields and a left axis on ECG. None of these matches an egg on a string.

So the descriptive sign maps cleanly onto one diagnosis.
\[\boxed{\text{Transposition of the great arteries}}\]