Heparin does not improve myocardial glucose metabolism suppression in [18 F]FDG PET/CT in patients with low β-hydroxybutyrate level.

Background: Inadequate myocardial glucose metabolism suppression (GMS) can hamper interpretation of cardiac [¹⁸F]fluorodeoxyglucose (FDG) positron emission tomography (PET/CT). Use of β-hydroxybutyrate (BHB) measurement before [¹⁸F]FDG injection has been proposed for predicting adequate GMS. However, limited information is available on BHB measurement in guiding preparations for [¹⁸F]FDG-PET/CT. The purpose of this study was to evaluate if point-of-care measured BHB is useful in guiding heparin premedication for cardiac [¹⁸F]FDG-PET/CT.

Results: 155 patients (82 male) had followed a high-fat, low-carbohydrate diet and fasted for at least twelve hours. For the first 63 patients, BHB was measured, but it was not used to guide premedication. For the subsequent 92 patients, heparin 50 IU/kg was injected intravenously 15-20 min before [¹⁸F]FDG injection if the BHB level was low (< 0.35 mmol/l). Cardiac [¹⁸F]FDG uptake pattern was evaluated visually and [¹⁸F]FDG uptake in the myocardium and blood pool were measured. Median BHB level was 0.4 (range 0.1-5.8) mmol/l. Eighty-eight patients (57%) reached a BHB level higher than 0.35 mmol/l. 112 patients (72%) had adequate GMS. In the high BHB group, 74 patients (84%) had adequate GMS, whereas of those with low BHB, only 38 (57%) had adequate GMS (p < 0.001). In the low BHB group, the prevalence of inadequate GMS was comparable in patients with and without heparin (44% vs. 42%, p = 0.875).

Conclusions: While high BHB predicts adequate GMS, unfractionated heparin does not improve GMS in patients with low BHB.