<i>Bartonella</i> Endocarditis Unmasking Heart Failure, Nephrotic Syndrome, and Pancytopenia in Repaired Tetralogy of Fallot: A Case Report

Introduction: Bartonella species are notable causes of culture-negative endocarditis, particularly in patients with prosthetic valves or congenital heart disease. These infections can present insidiously, mimicking other systemic illnesses and posing considerable diagnostic challenges due to their fastidious nature. Clinical Findings: A person in their 30’s with repaired tetralogy of Fallot and a Melody pulmonary valve presented with acute biventricular heart failure, nephrotic-range proteinuria, and pancytopenia. Initial assessments suggested cardiorenal syndrome. Despite negative routine cultures, persistent renal abnormalities and hypocomplementemia raised suspicion for glomerulonephritis. Subsequent polymerase chain reaction analysis of blood returned positive for Bartonella henselae, and positron emission tomography-computed tomography revealed focal uptake at the Melody valve, confirming prosthetic valve endocarditis. Clinical Course: The patient received aggressive diuresis, targeted antibiotic therapy with intravenous doxycycline and rifampin (later changed to ceftriaxone due to hepatoxicity) and multidisciplinary supportive care for multisystem organ dysfunction. Despite showing some clinical improvement over 32 days of hospitalization, the patient elected for self-directed discharge. Conclusions: This case illustrates the diagnostic difficulty of Bartonella endocarditis when it manifests with a complex triad of heart failure, nephrotic syndrome, and pancytopenia. The presentation can delay diagnosis by mimicking non-infectious systemic disorders. The utility of specific molecular diagnostics and advanced imaging is crucial in such culture-negative scenarios. Bartonella infection warrants consideration in patients with prosthetic cardiac materials who develop unexplained multisystem dysfunction.