title: Long fasting is effective in inhibiting physiological myocardial 18F-FDG uptake and for evaluating active lesions of cardiac sarcoidosis.
abstract: BACKGROUND
  F-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.
  
  
  METHODS
  We 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).
  
  
  RESULTS
  Myocardial 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.
  
  
  CONCLUSIONS
  LF 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.
authors.forename: Miyako
authors.initials: M
authors.lastname: Morooka
authors.affiliation: Department of Cardiology, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku-ku, Tokyo 162-8655, Japan. moroi@med.toho-u.ac.jp.
authors.forename: Masao
authors.initials: M
authors.lastname: Moroi
authors.forename: Kimiichi
authors.initials: K
authors.lastname: Uno
authors.forename: Kimiteru
authors.initials: K
authors.lastname: Ito
authors.forename: Jin
authors.initials: J
authors.lastname: Wu
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakagawa
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kubota
authors.forename: Ryogo
authors.initials: R
authors.lastname: Minamimoto
authors.forename: Yoko
authors.initials: Y
authors.lastname: Miyata
authors.forename: Momoko
authors.initials: M
authors.lastname: Okasaki
authors.forename: Osamu
authors.initials: O
authors.lastname: Okazaki
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Yamada
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: Michiaki
authors.initials: M
authors.lastname: Hiroe