Case Presentation: A 71-year-old man with history of coronary artery disease, aortic stenosis status post transcatheter aortic valve replacement (TAVR) two years ago, and ankylosing spondylitis presented to the emergency department for evaluation of 3 days of subjective fevers, worsening generalized weakness requiring one-person assist for ambulation, and tachycardia on his smart watch in the setting of three weeks of generalized weakness and myalgias. In the ED he was febrile to 39.1°C, tachycardic, and tachypneic with no oxygen requirement. Initial labs were notable for a WBC of 9.8 K/µL, normal lactate, and initial troponin of 16 ng/L (upper limit of normal 15 ng/L) with 2 hour recheck 16 ng/L. SARS-CoV-2 PCR was positive, and Influenza A, B, and RSV PCR were negative. Chest X-ray showed no evidence of pneumonia. He was admitted to medicine and started on remdesivir for COVID-19 infection.Blood cultures grew Streptococcus equinus (bovis group) in two of two bottles after 9 hours and ceftriaxone was initiated. The Infectious Disease team was consulted. Suspicion for infective endocarditis (IE) was high given the propensity of the organism to cause IE, the increased risk from the TAVR, and the duration of his symptoms. Due to COVID-19 isolation precautions, transesophageal echocardiogram (TEE) was deferred until day 5. He underwent initial evaluation with a transthoracic echocardiogram (TTE) and subsequent TEE both of which did not demonstrate evidence of IE. Because clinical index of suspicion remained elevated, the patient underwent Fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging which demonstrated diffuse near-circumferential activity surrounding the TAVR suggestive of infection. He completed six weeks of ceftriaxone and follow-up cultures two weeks after completion of therapy were negative. Outpatient colonoscopy demonstrated a tubular adenoma with high-grade dysplasia and negative margins.
Discussion: This case highlights the critical importance of maintaining a high index of suspicion for infective endocarditis (IE) in patients with S. equinus bacteremia, especially those with prosthetic heart valves. Despite negative transthoracic and transesophageal echocardiograms, the patient’s prolonged symptoms and bacteremia with an organism known for endocardial involvement warranted further investigation and the utilization of FDG-PET/CT was pivotal. In 2023, the International Society for Cardiovascular Infectious Diseases updated the Modified Duke Criteria to include FDG-PET/CT findings as a major criterion for diagnosing IE, particularly in prosthetic valve endocarditis (PVE) [1]. Meta-analyses report FDG-PET/CT sensitivity of 86% and specificity of 84% in PVE, increasing diagnostic sensitivity from 52–70% to 91–97% when incorporated into the Modified Duke Criteria [2].While the patient tested positive for SARS-CoV-2, his symptoms were not fully explained by COVID-19, emphasizing the importance of avoiding premature diagnostic closure.
Conclusions: This case emphasizes the importance of a thorough inpatient workup in diagnosing complex infections like IE, particularly in patients with prosthetic valves. FDG-PET should be considered in select cases when suspicion for infective endocarditis remains high despite other negative diagnostics. This case underscores the need for coordinated inpatient and outpatient care to ensure successful treatment and follow-up, including cancer screening through colonoscopy in patients with S. equinus bacteremia.
