F-18 FDG PET/CT scan in recurrent prosthetic valve endocarditis without detectable abnormality on echo: a case report

Abstract

Infective endocarditis poses many clinical and diagnostic challenge. The diagnosis of infective endocarditis is made by high index of clinical suspicion based on the American Heart Association modified Duke’s criteria, and the main imaging modality of choice is echocardiography. Here, we reported a case of recurrent infective endocarditis revealed by FDG PET/CT study despite completion of antibiotics and negative on echocardiography. A 38-year-old female with history of double-valve replacement for aortic stenosis presented with 1-week history of chest pain, dyspnea and intermittent fever. She was treated with 5 weeks of antibiotic with IV Cephalexin for prosthetic valve endocarditis. The repeated blood culture after IV antibiotic was negative for infection. She represented again with episodes of palpitation. Post-treatment blood investigation showed normal leukocyte level with increasing CRP and Troponin T level. The repeated blood culture and transesophageal echo was negative. The F-18 FDG PET/CT showed a mild hypermetabolic focus at the inferior basal myocardial wall adjacent to the prosthetic valve, however not involving the paraaortic region which is likely secondary to ongoing inflamed myocardium. As the fear of another relapse of endocarditis, oral suppression antibiotic therapy was continued for another 6 months. This case report illustrates a patient with a prosthetic valve replacement detected by F-18 FDG PET/CT, which one could have overlooked an endocarditis if one had relied on transesophageal echo (TEE) alone. F-18 FDG PET/CT is a promising adjunctive tool in the diagnostic workup of patients with suspected IE, particularly prosthetic device endocarditis where the TEE sensitivity is lower. In our patient, the positive F-18 FDG PET/CT governs the subsequent therapeutic consequences which include adjustment of antibiotic and length of treatment, and it prevents unnecessary intervention.