Coronary CT angiography in a 34-year-old woman with exertional chest pain shows a segment of the mid left anterior descending artery tunnelling through the underlying myocardium, with narrowing of the vessel lumen within the tunnelled segment. What is the diagnosis?

• A Intramural coronary haematoma
• B Myocardial bridge ✓
• C Spontaneous coronary artery dissection
• D Fibromuscular dysplasia of the LAD

Explanation

B myocardial bridge is a congenital variant in which a coronary segment takes an intramyocardial course beneath a band of muscle. On CCTA it appears as a vessel partially surrounded by myocardium with systolic luminal narrowing (the milking effect seen on invasive angiography). Dissection shows a flap or double lumen, intramural haematoma shows wall thickening without a lumen, and fibromuscular dysplasia affects medium sized muscular arteries such as the renal artery, not typically the LAD.

Reference: Grainger and Allison's Diagnostic Radiology, 7th ed.

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