18F-Fluorodeoxyglucose positron emission tomography/computed tomography as a diagnostic and follow-up tool in Coxiella burnetii endocarditis of prosthetic valve and aortic valved tube: a case report

Abstract

Background: European Society of Cardiology 2015 guidelines approved ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) as a useful diagnostic imaging technique in prosthetic valve endocarditis (PVE) and recent evidence seems to suggest a role of nuclear imaging in the follow-up of cardiovascular infections, but nowadays there are no sufficient data available.

Case summary: A 67-year-old male presented with fever, weight loss, and fatigue. His medical history included ulcerative colitis and a previous Bentall-De Bono surgical procedure in 2014. A previous recent hospitalization to a small community hospital did not reveal a clear aetiology for the fever: transeosophageal echocardiography showed dubious peri-prosthetic tissue alterations, interpreted as post-surgical fibrosis; consequently, the patient was discharged with steroid therapy. At admission in our ward, we repeated transoesophageal echocardiography that confirmed the peri-prosthetic alterations. Moreover, ¹⁸F-FDG PET/CT showed two hypermetabolic areas, one around the prosthetic tube in the aortic bulb and the other in relation with the prosthetic aortic valve. Serological test was positive for Coxiella burnetii infection with consequent beginning of a targeted antimicrobial therapy with oral doxicycline and hydroxychloroquine. Echocardiography, serology, and ¹⁸F-FDG PET/CT follow-up demonstrated a progressive response to treatment and clinical conditions of the patient gradually improved.

Discussion: According to guidelines, ¹⁸F-FDG PET/CT can be used in ambiguous PVE to improve diagnostic accuracy of standard techniques. In this case, ¹⁸F-FDG PET/CT combined with echocardiography and serological tests is used not only to better define diagnosis but also for treatment response monitoring during follow-up.

Keywords: 18F-FDG PET/CT; Aortic valved tube; Case report; Coxiella burnetii; Infective endocarditis; Q fever.

Figure 1

Transoesophageal echocardiography images. (A) and (B) show first exam performed in February 2019: echoic irregular material occupy the space between the native vessel, the prosthetic valve, and the aortic tube; (C) and (D) are images from follow-up exam on May 2019.

Figure 2

Basal ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography scan with corresponding no-attenuation-corrected images; (A) and (B) show the hypermetabolic area around the prosthetic tube in the aortic bulb (8 standardized uptake value); (C) and (D) show the hypermetabolic area in relation with the prosthetic aortic valve (6.9 standardized uptake value).

Figure 3

Second ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography scan with no-attenuation-corrected images (April 2019) showing a significant decrease of the inflammatory process. (A) and (B) are related to the prosthetic valved tube, (C) and (D) to the prosthetic aortic valve.

Figure 4

No-attenuation-corrected images in sequence, showing the good response to treatment from the basal scan—(A) and (D)—to an intermediate one—(B) and (E)—and to the last one—(C) and (F). (A), (B), and (C) are related to the valved aortic tube; (D), (E), and (F) refer to the aortic prosthetic valve.

Figure 5

Sequence of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography scan images, summarizing follow-up controls and showing progressive resolution of infective endocarditis. Images from (A) to (D) are related to the valved aortic tube, images from (E) to (H) show the aortic prosthetic valve.