Elevated NT-proBNP in the Setting of Ongoing Chest Infection Leading to Incidental Diagnosis of Infective Endocarditis-A Case Report

Infective endocarditis (IE) poses a known diagnostic challenge due to its variable clinical presentation. High suspicion for IE is generally driven by fever and positive blood cultures in the absence of an alternative focus of infection. We report an adult woman with a permanent pacemaker who presented with persistent fever, pleuritic chest pain and productive cough, diagnosed with right-sided community-acquired pneumonia. Blood cultures were negative; blood tests showed elevated inflammatory markers and an elevated white blood cell count, consistent with ongoing infection; and the NT-proBNP (obtained due to shortness of breath and evidence of pleural effusion on chest X-ray [CXR]) was markedly elevated, prompting transthoracic echocardiography (TTE). TTE demonstrated a large, irregular, independently mobile mass adherent to the pacemaker lead within the right atrium, prolapsing across the tricuspid valve into the right ventricle during diastole (≈2.3 × 1.0 cm), mild tricuspid regurgitation and normal biventricular systolic function. Transoesophageal echocardiography (TOE) confirmed a similar lead-adherent structure (≈2.5 × 1.0 cm), supporting a diagnosis of pacemaker-related IE in the appropriate clinical context. The patient was referred for complete device extraction at a specialist centre. This case highlights the diagnostic and management challenges of blood culture-negative endocarditis, the central role of echocardiography in the diagnosis of IE and the importance of integrating and interpreting imaging findings in the wider clinical context.