Cardiometabolic disorders affect myocardial [18F]fluorodeoxyglucose uptake- impact on diagnostic PET/CT imaging.

Background: Corresponding to impaired insulin response in skeletal muscle, insulin resistance may occur in the myocardium, suggesting a link between cardiometabolic disorders and cardiac glucose metabolism. We aimed to investigate whether cardiometabolic disorders predict myocardial [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) uptake suppression in cardiac positron emission tomography / computed tomography (PET/CT) following a ketogenic diet and fasting.

Results: The study included 100 patients undergoing [¹⁸F]FDG-PET/CT following a ketogenic diet of 1-2 days and a 12 h fast. Blood glucose, insulin, β-hydroxybutyrate (BHB), cholesterol, triglycerides and free fatty acid (FFA) levels were measured before [¹⁸F]FDG injection and later off-diet following overnight fast. The homeostatic model assessment-insulin resistance (HOMA-IR) value was calculated. Non-contrast computed tomography was used to assess the presence of fatty liver and visceral and subcutaneous fat areas. Suppression of myocardial [¹⁸F]FDG uptake was considered adequate if myocardial uptake was equal to or lower than the blood pool background. Compared to inadequate suppression, adequate suppression was associated with higher levels of BHB (median 0.26 mmol/l for inadequate and 0.43 mmol/l for adequate suppression, p = 0.004), FFA (0.58 mmol/l and 0.76 mmol/l respectively, p < 0.001), triglycerides (0.87 mmol/l and 1.12 mmol/l respectively, p = 0.028), and lower liver-spleen attenuation ratios (1.17 and 1.04 respectively, p = 0.013). Low HDL cholesterol, high triglycerides and off-diet HOMA-IR, as well as visceral adiposity, fatty liver and hypertension, predicted adequate suppression in men. Elevated BHB and FFA were significant predictors of adequate suppression in women.

Conclusions: Cardiometabolic disorders are associated with lower myocardial [¹⁸F]FDG uptake. Insulin resistance and several other cardiometabolic risk factors are associated with attenuated uptake, especially in men. In women, factors reflecting metabolic response to a ketogenic diet and fasting have a more pronounced effect on myocardial [¹⁸F]FDG uptake.