Improving the Diagnostic Performance of 18F-FDG PET/CT in Prosthetic Heart Valve Endocarditis [Original Research Article]

Background—18F-Fluorodeoxyglucose (FDG) Positron-Emission Tomography/Computed Tomography (PET/CT) was recently introduced as a new tool for the diagnosis of prosthetic heart valve (PV) endocarditis (PVE). Previous studies reporting a modest diagnostic accuracy may have been hampered by unstandardized image acquisition and assessment, as well as several confounders. The aim of this study was to improve the diagnostic performance of FDG PET/CT in patients suspected of PVE by identifying and excluding possible confounders, using both visual and standardized quantitative assessments.Methods—In this multicentre study, 160 patients with a PV (median age 62 [43-73]; 68% male; 82 mechanical valves; 62 biological; 9 TAVR; 7 other) who underwent FDG PET/CT for suspicion of PVE, as well as 77 patients with a PV (median age 73 [65-77]; 71% male; 26 mechanical valves; 45 biological; 6 TAVR) who underwent FDG PET/CT for other indications (negative control group), were retrospectively included. Their scans were reassessed by two independent observers blinded to all clinical data, both visually and quantitatively on available EARL-standardized reconstructions (European Association of Nuclear Medicine Research Ltd.). Confounders were identified using a logistic regression model, and subsequently excluded.Results—Visual assessment of FDG PET/CT had a sensitivity/specificity/PPV/NPV for PVE of 74%/91%/89%/78%, respectively. Low inflammatory activity (CRP <40mg/L) at the time of imaging and use of surgical adhesives during PV implantation were significant confounders, while recent valve implantation was not. After exclusion of patients with significant confounders, diagnostic performance values of the visual assessment increased to 91%/95%/95%/91%. As a semi-quantitative measure of FDG uptake, an EARL-standardized SUVratio of ≥2.0 was a 100% sensitive and 91% specific predictor of PVE.Conclusions—Both visual and quantitative assessment of FDG PET/CT have a high diagnostic accuracy in patients suspected of PVE. FDG PET/CT should be implemented early in the diagnostic work-up to prevent negative confounding effects of low inflammatory activity (e.g. due to prolonged antibiotic therapy). Recent valve implantation was not a significant predictor of false positive interpretations, but surgical adhesives used during implantation were.