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Competing Interests: Funding Support and Author Disclosures This study received infrastructure support from the Imperial College National Institute for Health Research Biomedical Research Centre, London, United Kingdom. Dr. Tarkin is supported by Wellcome Trust. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Objectives: This study investigated the incidence and clinical significance of arterial graft-associated uptake of fluorodeoxyglucose in large-vessel vasculitis (LVV)., Background: The role of 18 F-labeled fluorodeoxyglucose-positron emission tomography/computed tomography ([ 18 F]FDG-PET/CT) in the management of LVV remains to be defined. Although [ 18 F]FDG uptake at arterial graft sites raises concerns regarding active arteritis or infection, its clinical significance in LVV has never been formally studied., Methods: An observational prospective study sought to identify patients with Takayasu arteritis (TA) undergoing [ 18 F]FDG-PET/CT more than 6 months after graft surgery from a large cohort of patients from 2 tertiary referral centers. [ 18 F]FDG uptake by the graft and native arteries was scored on a scale of 0 to 3 relative to hepatic uptake, and periprosthetic maximum standardized uptake value (SUV max ) was calculated. Periprosthetic [ 18 F]FDG uptake in active disease was compared with that in inactive disease, and arterial progression was assessed by prospective magnetic resonance angiography (MRA)., Results: Twenty-six subjects with TA were enrolled. All were afebrile with negative blood culture. Periprosthetic uptake was significant in 23 of 26 patients, and the mean SUV max was 4.21 ± 1.46. Median periprosthetic [ 18 F]FDG uptake score (3; interquartile range [IQR]: 3 to 3) was higher than in native aorta (1; IQR: 0 to 1; p < 0.001). Graft-specific [ 18 F]FDG uptake was unrelated to disease activity. Despite the high frequency of graft-associated [ 18 F]FDG uptake, sequential MRAs did not reveal arterial progression in 25 of 26 patients; the 1 remaining case showed minor progression limited to native arteries. Nine patients underwent repeated PET/CT scanning without showing changes in graft-specific uptake, despite increased treatment., Conclusions: Significant [ 18 F]FDG uptake that is confined to arterial graft sites in patients with LVV does not reflect clinically relevant disease activity or progression. To minimize exposure to immunosuppression and in the face of negative blood culture, clinically quiescent arteritis, normal or stably raised C-reactive protein levels, we elected not to escalate treatment and monitor progression with MRA., (Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)