Which imaging test identifies scar tissue in suspected cardiac sarcoidosis?

• A. CMR-LGE
• B. FDG-PET
• C. Echocardiography
• D. CT angiography

Answer: (A)

The key idea is tissue characterization: identifying scar versus active inflammation in the heart. Cardiac MRI with late gadolinium enhancement visualizes scar tissue because gadolinium contrast pools in areas with expanded extracellular space, which occurs in fibrotic or scarred myocardium. This produces bright areas on LGE images, often in a subepicardial or mid-wall distribution typical of sarcoid scar, and offers high-resolution detail of scar burden and location. This makes it the best test for identifying myocardial scar in suspected cardiac sarcoidosis and it also provides information on heart function and, with additional sequences, inflammation.

FDG-PET, while excellent for detecting active inflammation by showing metabolic activity, does not map scar as effectively because scar tissue generally lacks metabolism. Echocardiography shows function and wall motion abnormalities but cannot characterize scar tissue directly. CT angiography focuses on coronary anatomy and vessels, not scar tissue.