Are 18F-fluorodeoxyglucose positron emission tomography results reliable in patients with ascending aortic grafts? A prospective study in non-infected patients.

OBJECTIVES

Our goal was to define characteristic patterns of 18F-fluorodeoxyglucose in non-infected patients with ascending aortic prosthetic grafts during the first year after surgery.

METHODS

18F-fluorodeoxyglucose positron emission tomography (PET)/computed tomography (CT) was performed at 3, 6 and 12 months postoperatively in 26 uninfected patients. Clinical, analytical and microbiological (blood culture) assessments were performed to confirm the absence of infection. FDG uptake intensity [measured through maximum standardized uptake values (SUVmax) and the target-to-background ratio] and distribution patterns were obtained. Models of generalized estimating equations were used to assess the evolution of the SUVmax over time. The results were compared to those in our endocarditis-over-ascending-aortic-graft series database. The receiver operating characteristic curves of the control group and the 12-month group were assessed.

RESULTS

All patients showed increased uptake in all areas. The uptake pattern was heterogeneous in 47.4%, 43.5% and 42.3% at 3, 6 and 12 months. The means and standard deviations of the SUVmax in the graft were 4.80 (±0.99), 4.28 (±0.88) and 4.14 (±0.87) at 3, 6 and 12 months after surgery. A comparison of all values obtained in the 6th and 12th months compared to those from the 3rd month revealed a slow decrease that may persist after the first year. The cut-off value of SUVmax of 4.24 had an overall sensitivity of 84.6% and specificity of 57.7% for patients seen at 12 months.

CONCLUSIONS

Non-infected ascending aortic grafts showed no predominant uptake pattern; they also showed increased 18F-fluorodeoxyglucose activity that could persist beyond the first year. Caution is therefore recommended when interpreting PET/CT images obtained during the first year after surgery.