On FDG PET-CT performed for lung cancer staging, the primary mass in the right upper lobe shows SUVmax 12. A 1.2 cm right hilar lymph node shows SUVmax 3.5. A focus of increased FDG uptake is also noted in the right cardiac ventricle wall. What is the most likely cause of this cardiac FDG uptake?

• A Cardiac metastasis from lung cancer
• B Sarcoidosis involving the myocardium
• C Post-radiation myocarditis
• D Physiological myocardial FDG uptake — the normal heart preferentially uses glucose ✓

Explanation

The myocardium normally utilizes both fatty acids and glucose for metabolism. In the fed state, glucose metabolism predominates and normal physiological FDG uptake in the left (and sometimes right) ventricle is common, representing a major interpretive pitfall on oncological PET-CT. This is reduced by prolonged fasting (≥6 hours), high-fat low-carbohydrate diet prior to the scan, or using heparin to shift myocardial metabolism toward fatty acids. Cardiac sarcoidosis produces focal patchy uptake, usually in the basal septum; cardiac metastases are rare. The clinical context of a standard oncological scan favors physiological uptake as the most likely explanation.

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

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Written and medically reviewed by the StethoPrep medical team.