Abstract
BackgroundF-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a promising modality for detecting active lesions of cardiac sarcoidosis (CS). However, determining whether 18F-FDG uptake in the myocardium is physiological is challenging due to metabolic shift in myocardial cells. Although methods for inhibiting physiological myocardial 18F-FDG uptake have been proposed, no standard methods exist. This study therefore aimed to compare the effect of an 18-h fast (long fasting (LF)) with heparin loading plus a 12-h fast (HEP) before 18F-FDG PET scan.MethodsWe analyzed the effects of LF and HEP on the inhibition of physiological myocardial 18F-FDG uptake in healthy subjects (18 in HEP and 19 in LF) and in patients with known or suspected CS (96 in HEP and 69 in LF). In CS, the lower uptake of 18F-FDG in the myocardium was evaluated. A visual four-point scale was used to assess myocardial 18F-FDG uptake in comparison with hepatic uptake (1 lower, 2 similar, 3 somewhat higher, 4 noticeably higher).ResultsMyocardial 18F-FDG uptake was 1.68 ± 1.06 in LF and 3.17 ± 1.16 in HEP in healthy subjects (p < 0.0001), whereas it was 1.48 ± 0.99 in LF and 2.48 ± 1.33 in HEP in CS patients (p < 0.0001). Logistic regression and regression trees revealed the LF was the most effective in inhibiting myocardial 18F-FDG uptake. In addition, serum free fatty acid levels on intravenous 18F-FDG injection were a possible biomarker.ConclusionsLF is effective in inhibiting myocardial 18F-FDG uptake, and consequently, it could be useful for evaluating active lesions of CS in 18F-FDG PET images.
Highlights
F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a promising modality for detecting active lesions of cardiac sarcoidosis (CS)
Assessing inflammatory cardiomyopathies using 18F-FDG PET can be challenging because the radiotracer accumulates in normal myocardium, a phenomenon known as physiological uptake; this is problematic because the myocardial uptake of 18F-FDG is heterogeneously based on metabolic shifts in myocardial cells [6,7,8]
Based on the polar map patterns observed in healthy subjects, we considered a diffuse uptake or basal ring-like and/or lateral uptake to be physiological in patients with suspected or known cardiac sarcoidosis
Summary
F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a promising modality for detecting active lesions of cardiac sarcoidosis (CS). Determining whether 18F-FDG uptake in the myocardium is physiological is challenging due to metabolic shift in myocardial cells. 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a promising modality for detecting ‘active’ lesions in various inflammatory cardiovascular diseases, including cardiac involvement of sarcoidosis, myocarditis, and vascular diseases such as Takayasu's arteritis, giant cell arteritis, and atherosclerosis [3,4,5]. Assessing inflammatory cardiomyopathies using 18F-FDG PET can be challenging because the radiotracer accumulates in normal myocardium, a phenomenon known as physiological uptake; this is problematic because the myocardial uptake of 18F-FDG is heterogeneously based on metabolic shifts in myocardial cells [6,7,8]
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