Journal of Advances in Medicine and Medical Research

Background: The diagnosis of infective endocarditis (IE) remains complex, and the modified Duke criteria have limitations, particularly in patients with prosthetic valves or cardiac devices. This study evaluates the diagnostic contribution and clinical impact of 18F-FDG PET/CT in patients with suspected IE and inconclusive initial evaluations.

Materials and Methods: We conducted a retrospective analysis of 21 18F-FDG PET/CT scans performed for suspected IE between January 2020 and December 2025 in 18 patients initially classified as Duke ± (possible) or Duke − (rejected). The final diagnosis of IE was established by multidisciplinary consensus during follow-up (minimum 3 months). PET/CT image analysis focused on the cardiac area and systematically searched for distant septic foci. Semi-quantitative parameters (SUVmax, target-to-background ratios) were recorded. Diagnostic performance was calculated with 95% confidence intervals, and clinical impact (reclassification rate and management changes) was quantified.

Results: Of the 21 scans, 15 were performed in patients with prosthetic cardiac material. PET/CT was positive in 9 of these 15 patients (60%), demonstrating periprosthetic valvular hypermetabolism in 6 patients and device-related hypermetabolism in 3 patients. Extracardiac infectious foci were identified in 6 patients (40%). One false-negative result occurred in a patient on prolonged antibiotic therapy for fungal endocarditis. In the 6 patients with suspected native valve IE, all PET/CT scans were negative, and IE was subsequently excluded. Diagnostic performance in the prosthetic material group showed: sensitivity 90% (95% CI: 54.1–99.5%), specificity 100% (95% CI: 46.3–100%), PPV 100% (95% CI: 62.9–100%), NPV 83.3% (95% CI: 36.5–99.1%). PET/CT reclassified 8 of 16 patients (50%) from "possible" to "definite" IE and influenced clinical management in 12 of 21 scans (57.1%), including treatment intensification, detection of extracardiac foci requiring intervention, avoidance of unnecessary procedures, and surgical planning guidance.

Conclusion: 18F-FDG PET/CT provides significant diagnostic value in suspected IE involving prosthetic valves or cardiac devices, with high sensitivity and specificity when echocardiography is inconclusive. The examination not only aids in confirming cardiac infection but also provides crucial whole-body assessment by detecting peripheral septic emboli and extracardiac foci. With a 50% reclassification rate and 57% impact on management, PET/CT should be performed early in the diagnostic pathway for appropriately selected patients according to 2023 ESC guidelines.