A 42–year–old man presented with persistent dyspnea for 10 months that had worsened over the last month. He has had multiple hospital admissions for congestive heart failure and anemia of chronic disease. An extensive gastrointestinal, cardiac and respiratory workup had been normal. Transthoracic echo (TTE) 2 weeks prior failed to show systolic or diastolic dysfunction. On exam, significant findings included conjunctival pallor, bibasilar crackles, 4/6 systolic ejection murmur with carotid radiation as well as a 2/4 early diastolic decrescendo murmur at the left upper sternal border. An S3 heart sound was present and a water hammer pulse noted at the radial and brachial arteries. Hepatosplenomegaly was prominent as well as bilateral lower extremity edema. Laboratory data revealed a hemoglobin of 7.4, creatinine 2.5, and BNP 1552; urinalysis showed 3+ blood, >100 RBC’s and 2+ protein. On hospital day 2, he developed a diffuse lower extremity macular rash consistent with embolic phenomenon. A skin biopsy and blood cultures were obtained. Empiric antibiotics were started for infective endocarditis (IE). Repeat TTE revealed a dilated left atrium with severe aortic regurgitation, RSVP of 70 mm Hg and a 0.6 × 1.3 cm mobile mass on the aortic valve. Pathologic evaluation of the valve after surgical removal showed multiple vegetations on all leaflets. Blood and intraoperative cultures remained negative. Further workup ensued to detect organisms responsible for blood–culture–negative endocarditis. Bartonella henselae IgG was found to be >1:1024 and confirmatory 16s RNA PCR was positive. Further history revealed the patient had two young cats that were given away just prior to the start of his recurrent dyspnea.
Up to 20% of IE cases as defined by the modified Duke Criteria are blood culture negative. Empiric antibiotics are implicated in the majority of these cases and have been sited to reduce bacterial recovery by 35–40%. Other concerning causes include inadequate detection techniques and fastidious intracellular microorganisms, such as Bartonella. Conventional gram–stain and culture for Bartonella are positive only 1–10% of the time. Clinical manifestations of B. henselae infection include intra–ocular changes, encephalopathy, lymphadenopathy, relapsing bacteremia and fever. Symptoms can occur weeks after exposure and last for months without treatment. Another limitation in promptly diagnosing endocarditis is the poor sensitivity of TTE. Appropriateness criteria for echocardiography have been developed to help standardize and optimize its use. Transesophageal echo has been proposed to be essential in all cases of suspected IE.
Hospitalists often care for patients that are re–admitted with exacerbations of chronic disease. This case of culture negative IE highlights the importance of evaluating the available data at presentation as well incorporating new findings to avoid premature closure and anchoring bias.