Diagnosing Prosthetic Valve Endocarditis Despite a Negative Work-Up

A 38-year-old patient with a prosthetic aortic valve had weeks of fever and respiratory symptoms. Although endocarditis was suspected early, numerous blood cultures and echocardiograms failed to confirm the diagnosis. Key questions were: What is a broad differential diagnosis for the above symptoms? What is unique about diagnosing prosthetic valve endocarditis compared with native valve endocarditis? What other imaging modalities are useful for diagnosing prosthetic valve endocarditis when initial echocardiographic evaluation is negative? What organisms are classically implicated in "culture negative" infective endocarditis? Serial blood cultures and multimodal imaging, including cardiac positron emission computed tomography with 18F-fluorodeoxyglucose, lead to a diagnosis of prosthetic valve endocarditis with a HACEK (<i>Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella</i>) pathogen. Repeat blood cultures and serial multimodal imaging are paramount to diagnosing prosthetic valve endocarditis, particularly when caused by a fastidious organism.