Page 163 - Small Animal Internal Medicine, 6th Edition

CHAPTER 6 Acquired Valvular and Endocardial Disease 135

BOX 6.4
VetBooks.ir Criteria for Diagnosis of Infective Endocarditis*

Definite Endocarditis by Pathologic Criteria
Positive echocardiogram for infective endocarditis
Pathologic (postmortem) lesions of active endocarditis with Evidence of endocardial involvement
evidence of microorganisms in vegetation (or embolus) (oscillating mass on heart valve or supportive
or intracardiac abscess structure or in path of regurgitant jet, or evidence of
cardiac abscess)
Definite Endocarditis by Clinical Criteria New valvular regurgitation, especially if more than mild
Two major criteria (below), or aortic regurgitation; increase or change in
One major and two to three minor criteria, or preexisting murmur is not sufficient evidence
Five minor criteria Minor Criteria
Possible Endocarditis Subaortic stenosis or other predisposing cardiac condition
Findings consistent with infectious endocarditis that fall (see p. 132)
short of “definite” but not “rejected” Fever
Thromboembolic disease, including major arterial emboli,
Rejected Diagnosis of Endocarditis septic infarcts
Firm alternative diagnosis for clinical manifestations Immune-mediated disease, including glomerulonephritis,
Resolution of manifestations of infective endocarditis with 4 polyarthritis, or positive antinuclear antibody or
or fewer days of antibiotic therapy rheumatoid factor tests
No pathologic evidence of infective endocarditis at Echocardiogram consistent with infective endocarditis, but
surgery or necropsy not meeting major criteria above
High seroreactivity (e.g., titer ≥1 : 1024) or positive PCR
Major Criteria test for Bartonella spp. †
Positive blood cultures Medium to large dog (>15 kg) †
Typical microorganism for infective endocarditis from Positive blood culture not meeting major criterion, as
two separate blood cultures previously mentioned
Persistently positive blood cultures for organism (Rare in dogs and cats: repeated nonsterile IV drug
consistent with endocarditis (samples drawn >12 administration)
hours apart, or three or more cultures drawn ≥1
hour apart)

*Adapted from modified Duke criteria for endocarditis.
† Proposed minor criterion for endocarditis in dogs.

three to four blood samples of at least 10 mL are collected collected in plastic ethylene diamine tetraacetic acid (EDTA)
aseptically over 24 hours for bacterial culture, with more tubes then frozen at -70° C until plated. Molecular testing
than an hour elapsing between collections. Sampling during using polymerase chain reaction (PCR) amplification of spe-
a fever spike or, if antibiotic therapy has already been given, cific Bartonella gene segments is an important diagnostic
at the time of drug trough concentration may increase diag- tool. However, PCR amplification directly from blood or
nostic yield. A shorter sampling period of 3 to 4 hours could other body fluid samples often does not identify Bartonella
be used for critical patients before beginning empiric antibi- DNA because of low circulating bacterial levels or intermit-
otic therapy. Different venipuncture sites should be used for tent bacteremia, and bacterial sequestration within endothe-
each sample. Blood collection from an indwelling IV cath- lial cells and vegetative lesions. Positive results are more
eter is not recommended. Both aerobic and anaerobic cul- likely in immunosuppressed patients. A combined technique
tures have been recommended, although the value of routine using preenrichment culture of aseptically collected blood
anaerobic culture is questionable. Prolonged incubation (3-4 (or body fluid or surgical tissue samples) in BAPGM fol-
weeks) is recommended, because some bacteria are slow lowed by a high-sensitivity PCR assay can increase diagnos-
growing. tic yield and is commercially available (Galaxy Diagnostics
Bartonella spp are an important cause of culture-negative Inc.; www.galaxydx.com). Aseptic handling of samples is
endocarditis in some regions. These organisms are especially important to avoid contamination. Serologic testing (includ-
difficult to identify on blood cultures. Use of specialized ing immunofluorescent antibody [IFA] or enzyme-linked
culture conditions and an enriched insect cell culture immunosorbent assay [ELISA] tests) also can help, although
medium (Bartonella α Proteobacteria growth medium; Bartonella infection can cause variable seroreactivity. Some
BAPGM) or heart infusion agar may increase the likelihood cases develop high titers to Bartonella spp., but others (~half
of growing these organisms. Blood can be aseptically of dogs) are not seroreactive. The particular Bartonella