Find the narrowing at the isthmus beyond the left subclavian artery, measure it against the diaphragmatic aorta, show its significance (collaterals, gradient), and look for the associated lesions — bicuspid aortic valve above all.
Orient first
- Coarctation is a shelf-like narrowing at the aortic isthmus, usually just distal to the left subclavian artery; long-standing obstruction recruits intercostal and internal mammary collaterals.
- Associations: bicuspid aortic valve (common), arch hypoplasia, VSD, intracranial aneurysms.
- After repair or stenting the questions change: recoarctation, aneurysm or pseudoaneurysm at the repair site, and aortic dilatation.
Acquire the study
- CXR; contrast-enhanced MRA or CTA of the thoracic aorta (ECG-gated for the root) with MPR; MRI phase contrast above and below the narrowing.
The manoeuvre
- Rib notching on the inferior margins of the posterior 3rd–9th ribs (collaterals), usually after childhood.
- Figure-3 sign of the left upper mediastinal contour (pre-stenotic dilatation, the coarctation, post-stenotic dilatation).
What confirms it
- Focal isthmic narrowing with measured minimum diameter and ratio to the diaphragmatic aorta, plus collaterals or a flow gradient.
What licenses you to exclude it
- A normal isthmus on candy-cane MPR with no collaterals and normal descending-aortic flow excludes haemodynamically significant coarctation.
The classic misread
- Measuring on an axial slice through a tortuous isthmus — overcalls or misses the narrowing.