Challenging case of chronic Q fever endocarditis: usefulness of 18F-FDG PET/CT in the diagnosis and follow-up

Abstract

Diagnosis of infective endocarditis can be challenging for clinicians, especially when involving prosthetic valves. Recent data suggest that ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) could be a useful diagnostic tool in this setting. Here, we report a case of a patient with an aortic biological prosthesis who presented with a history of fever and fatigue. Echocardiograms were negative for vegetations. The ¹⁸F-FDG PET/CT revealed an infective process of the valve and serological tests were positive for chronic Coxiella burnetii infection. Specific treatment for chronic Q fever endocarditis was, therefore, started and the response was monitored using ¹⁸F-FDG PET/CT. This case highlights the challenges and pitfalls clinicians face when confronted with prosthetic valve endocarditis and the use of ¹⁸F-FDG PET/CT for diagnosis and follow-up.

Keywords: cardiovascular medicine; infections; infectious diseases; radiology; valvar diseases.

Figure 1

Shows axial images of CT (A), 18F-FDG PET (B), non-attenuation-correction PET (C) and fused PET/CT images (D) performed at baseline (I), after 4 (II), 8 (III) and 16 (IV) months on treatment. In order to minimise physiological 18F-FDG myocardial uptake, the patient was asked to observe a very low carbohydrate, high protein and high-fat diet the day before each PET imaging and then to fast overnight on the day before imaging. At baseline, 18F-FDG PET images show increased radiopharmaceutical uptake around the aortic valve prosthesis, with a focal pattern on the posterior surface (red arrows; I: SUVmax 6.1). 18F-FDG uptake gradually decreases in subsequent PET/CT scans (red arrows; II: SUVmax 3.8; III: SUVmax 3.7) until it becomes not significant in the last imaging (red arrows; IV: SUVmax 2). 18F-FDG PET, 18F-fluorodeoxyglucose positron emission tomography. SUV, standardized uptake value.