Enhancing the Diagnosis of Infective Endocarditis: The Role of 18F-FDG PET/CT

Introduction: Infective endocarditis (IE) poses diagnostic challenges due to its diverse clinical presentations. Traditionally, diagnosis relies on echocardiography, microbial analysis, and clinical assessments as per the Modified Duke Criteria (MDC), but their accuracy is notably inconsistent, especially in cases involving prosthetic valves (PV) and cardiac-implantable electronic devices (CIEDs). This variability has prompted the inclusion of additional imaging techniques in diagnostic protocols. Among these, 18F-fluorodeoxyglucose PET/CT (18F-FDG PET/CT) has emerged as a key modality, evolving in its role and application. We aim to thoroughly evaluate the utility of 18F-FDG PET/CT in accurately identifying IE across various contexts, including native valves (NV), PV, and CIEDs, to understand better its optimal application in the complex landscape of IE diagnosis.

Methods: Utilizing databases such as Google Scholar and PubMed, we conducted a focused search with keywords 'PET/CT,' '18F-FDG,' 'infective endocarditis,' and 'IE.' This enabled us to compile a comprehensive collection of literature on the role of PET/CT in IE, from which we extracted and synthesized key findings.

Results: 18F-FDG PET/CT has become a pivotal tool in the diagnosis of prosthetic valve endocarditis (PVE), particularly valuable in cases where echocardiographic results are inconclusive. This imaging modality enhances diagnostic accuracy by reducing the number of cases categorized as 'possible IE' under Modified Duke Criteria (MDC) and correctly reclassifying them as definitive IE. It's especially useful in instances of persistent IE suspicion despite repeatedly negative blood cultures. The combination of PET with CT angiography (CTA) is superior to PET with non-contrast CT in detecting IE, especially in patients with prosthetic valves and cardiac-implantable electronic devices (CIEDs). In PVE, PET/CTA excels in identifying valvular abnormalities like thrombus or vegetation, local complications including pseudoaneurysms and perivalvular abscesses, and systemic issues such as septic emboli. This modality is also more effective than echocardiography in detecting endocarditis related to transcatheter aortic valve implantation (TAVI), where metal artifacts can limit echocardiographic assessment. While PET/CT is less sensitive than echocardiography for native valve endocarditis (NVE), its diagnostic sensitivity improves significantly when integrated with MDC. It also assists in uncovering asymptomatic peripheral complications in NVE cases. However, the accuracy of 18F-FDG PET/CT can be affected by prior antibiotic treatment, leading to false negative results, and by recent surgery, potentially causing false positives. In the early postoperative period (1-3 months after prosthetic valve surgery), leukocyte scintigraphy may yield more reliable results, offering an alternative imaging strategy in these complex clinical scenarios.

Conclusions: 18F-FDG PET/CT enhances the diagnostic precision of Modified Duke Criteria (MDC) for Infective Endocarditis (IE), especially in prosthetic valve endocarditis (PVE) and cardiac-implantable electronic device-related IE (CIED-IE). PET/CTA often outperforms PET with non-contrast CT in these scenarios. While 18F-FDG PET/CT doesn't significantly supplement echocardiography in native valve endocarditis (NVE), its high sensitivity and ability to detect both symptomatic and asymptomatic dissemination sites make it a valuable tool in a broad spectrum of clinical applications for IE.