The heart can display intense FDG uptake in the fed state. With sufficient fasting (at least > 6 hrs) the heart shifts to fatty acid metabolism to fulfill its energy requirements, and FDG myocardial uptake decreases (most of the time) to blood pool levels. In practice, patients demonstrate variable and non-uniform uptake even following an overnight fast, and this is likely related to the non-uniform transition from glucose to fatty acid metabolism. This transition usually occurs last in the left ventricular base.

Possible limitations:
Evaluation of disease involving the pericardium, adjacent lung, and mediastinum can be difficult, and in certain cases heart uptake might mimic discrete foci of disease in the mediastinum.

Preventive measures:
Ensure adequate fasting as much as possible to limit cardiac muscle uptake.