Objectives: To investigate the incidence and clinical significance of arterial graft-associated uptake
of fluorodeoxyglucose in large vessel vasculitis (LVV).
Background: The role of [18F]-fluorodeoxyglucose-positron emission tomography/computed
tomography (18F-FDG-PET/CT) in the management of LVV remains to be defined. Although 18FFDG
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 18F-FDG-PET/CT more than 6 months after graft surgery, from a large cohort of
patients from two tertiary referral centres. 18F-FDG uptake by the graft and native arteries was
scored on a 0 to 3 scale against hepatic uptake, and peri-prosthetic maximum standardized uptake
value (SUVmax) was calculated. Peri-prosthetic 18F-FDG uptake in active or inactive disease was
compared 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.
Peri-prosthetic uptake was significant in 23/26 patients, with a mean SUVmax of 4.21±1.46. Median
peri-prosthetic 18F-FDG uptake score (3, IQR 3-3) was higher than in the native aorta (1, IQR 0-1,
p<0.001). Graft-specific 18F-FDG uptake was unrelated to disease activity. Despite the high
frequency of graft-associated 18F-FDG uptake, sequential MRAs did not reveal arterial progression
in 25/26 patients; the remaining case showed minor progression limited to native arteries. Nine
patients repeated PET/CT scanning without changes in graft-specific uptake despite increased
treatment.
Conclusion: Significant 18F-FDG uptake confined to arterial graft sites in patients with LVV does
not reflect clinically relevant disease activity or progression. To minimise exposure to
immunosuppression and in the face of negative blood culture, clinically quiescent arteritis, normal
or stably raised CRP levels, we elect not to escalate treatment and monitor progression with MRA.