Performance of 18F-FDG PET/CT in the diagnosis of endocarditis
Authors: Desgranges F , Kamani C , Rotzinger D , Guery B , Ianculescu N , Auberson D , Tzimas G , Hugelshofer S , Tozzi P , Kirsch M , Monney P , Prior J , Papadimitriou-Olivgeris M 
Published: November 2023

Abstract

Background
Infectious endocarditis (IE) remains a diagnostic challenge that requires a combination of clinical, microbiology, and imaging clues. Usefulness of 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (18F-FDG PET/CT) in the diagnostic algorithms has been demonstrated. However, performances of 18F-FDG PET/CT vary greatly between studies and types of IE. 18F-FDG PET/CT may have a better sensitivity for prosthetic valve IE (PVE) than for native valve IE (NVE) or cardiac implantable electronic devices IE (CIED-IE).

Purpose
Define the performance of 18F-FDG PET/CT after echocardiography in the diagnosis of all types of IE in our institution.

Methods
This hybrid study was conducted at a university hospital from January 2014 to June 2022 (retrospective cohort: 2014-17 and prospective cohort: from 2018 onwards). Adult patients with a suspected valvular or CIED-IE were included. Realization of 18F-FDG PET/CT was left at the discretion of the treating physician or by an endocarditis-team that was established in 2018. 18F-FDG PET/CT analysis were performed nuclear medicine physicians and radiologists (when the CT was contrast-enhanced), based on visual interpretation. The final diagnosis of possible or definite IE was defined by the endocarditis team according to European Society of Cardiology 2015 modified Duke criteria.

Results
During the study period, 280 18F-FDG PET/CT with interpretable intracardiac results were performed for a clinical suspicion of IE in 247 patients. A final IE diagnosis was retained for 116 episodes (41%; 81 definite and 35 possible IE), among which 102 valvular (59 NVE and 44 PVE) and 20 CIED-IE. 18F-FDG PET/CT showed radiologic signs of endocarditis in 60 episodes (21%) with an overall specificity, sensitivity, positive and negative predictive values (PPV, NPV) of 97.6%, 48.3%, 93.3%, and 72.7%, respectively. This led to an overall accuracy of 77.1% and between 80 to 85% when looking at specific types of IE. Performances of 18F-FDG PET/CT for each type of IE are shown in Figure 1. Addition of 18F-FDG PET/CT to the modified Duke criteria reclassified the diagnosis in 37 cases: from possible/rejected IE to definite IE in 25 cases (21.5%) and from rejected IE to possible IE in 12 cases (10.3%) (Figure 2). Figure 2 shows a Shankey diagram of classification of episodes by clinical Duke criteria without 18F-FDG PET/CT results (left side), clinical Duke criteria with 18F-FDG PET/CT results (center) and final diagnosis retained by clinicians (right side).

Conclusion
Use of 18F-FDG PET/CT in a multimodal diagnostic approach led to an acceptable accuracy for all types of IE in our center. Signs of endocarditis on 18F-FDG PET/CT should be interpreted as confirmatory, while absence of sign do not efficiently rule out this diagnosis. In this cohort, 18F-FDG PET/CT helped to reclassify 15.9% of possible or rejected IE.Performance of 18F-FDG PET/CTShankey diagram of IE classification