Heparin does not improve myocardial glucose metabolism suppression in patients with low betahydroxybutyrate level

Abstract Background/introduction Inadequate myocardial glucose metabolism suppression (GMS) can hamper diagnostic PET/CT imaging with [18F]FDG. β-hydroxybutyrate level (BHB) measurement prior to [18F]FDG injection is a newly proposed method of pre-evaluation of adequate GMS. However, more knowledge is needed, if BHB can be used to guide the preparation protocol (diet, fasting or premedication). Purpose The aim of our study was to evaluate if point-of-care measured BHB can be used to guide use of heparin premedication for cardiac [18F]FDG-PET/CT. Methods 139 patients [78 male, median age 58 (19-78) years] with clinical indication for cardiac [18F]FDG PET/CT were recruited. All patients had followed a high fat, low carbohydrate diet for one day and fasted for at least twelve hours. For the first 64 patients, BHB was measured, but it was not used to guide premedication. For the next 75 patients, iv. heparin 50 IU/kg was injected 15-20 minutes before FDG injection, if BHB was low (less than 0.35 mmol/l), whereas those with high BHB (more than 0.35 mmol/l) continued without heparin. [18F]FDG uptake pattern was evaluated visually using grades "no uptake", "focal uptake", "isolated lateral wall uptake", "basal ring", "diffuse uptake" and "focal on diffuse". "No uptake" and "focal uptake" were considered as adequate GMS. Statistical significance of the difference in uptake patterns was evaluated using the Pearson’s chi-square test. Results Median BHB was 0.4 (0.1-5.8) mmol/l. Half of the patients (76, 55 %) reached BHB higher than 0.35 mmol/l. Still, 102 patients (74 %) had adequate GMS. In high BHB group, 65 patients (86 %) had adequate GMS, whereas of those with low BHB, only 37 patients (59 %) had adequate GMS (p<0.001). In low BHB group prevalence of inadequate GMS was comparable in patients with and without heparin (42 % vs. 41 %, p=0.941) Results for the whole scale of visual distribution patterns can be seen in figure 1. Conclusion(s) Patients with high BHB have a high percentage of adequate GMS, whereas in patients with low BHB the probability of adequate GMS is significantly lower. Unfractionated heparin does not seem to improve myocardial GMS in patients with low BHB. Thus, high BHB should be pursued, and a longer diet might be needed for those with low initial BHB.