Written & reviewed by: Kinase Medical Team · Last reviewed: 30 September 2026 · Editorial policy
Key features
- Upturned cardiac apex from right ventricular hypertrophy.
- Concave pulmonary bay because the pulmonary artery is small (reduced outflow through subpulmonic stenosis).
- Lung fields are oligaemic (reduced pulmonary blood flow).
- Right-sided aortic arch in about 25% of cases.
- Four components: large VSD, right ventricular outflow tract obstruction, overriding aorta, right ventricular hypertrophy.
- The most common cyanotic congenital heart disease.
Differential diagnosis
| Condition | How to tell it apart |
|---|---|
| Transposition of the great arteries | 'Egg-on-a-string' — globular heart with a narrow superior mediastinum. |
How it appears in NEET PG
Paediatric chest films are frequent image questions; this one is matched with a cyanotic child and asks for the lesion or its components.
Frequently asked questions
Why is the heart boot-shaped in tetralogy of Fallot?
Right ventricular hypertrophy lifts the cardiac apex, and the small pulmonary artery leaves a concave segment on the upper left heart border, together giving a boot outline.
What are the four components of tetralogy of Fallot?
A large ventricular septal defect, right ventricular outflow tract obstruction, an overriding aorta and right ventricular hypertrophy.
How common is a right-sided aortic arch in tetralogy of Fallot?
It is seen in about a quarter of cases.
Sources
- Radiopaedia — Boot-shaped heart
- Radiopaedia — Tetralogy of Fallot
- Radiopaedia — Egg-on-a-string sign (heart)
- Robbins Basic Pathology (textbook)
Keep practising
- NEET PG Radiology previous-year questions
- Pneumoperitoneum (Air Under the Diaphragm)
- Sigmoid Volvulus (Coffee Bean Sign)
- Extradural (Epidural) Haematoma on CT
- All clinical images
For exam preparation and medical education only — not a substitute for clinical judgement, diagnosis or treatment of any patient.