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Endocarditis, Infective 295

murmur (e.g., from SAS). The presence of a and monocytosis), thrombocytopenia, hypo- or in cases of culture-negative IE, empirical
albuminemia, and azotemia are common.
antibiotic therapy is warranted.
diastolic murmur in a systemically ill animal • Urinalysis may reveal pyuria, hematuria, and • Empirical IV antibiotic therapy in dogs
VetBooks.ir • Respiratory abnormalities (e.g., tachypnea, proteinuria. Bacteruria may be present. Urine may include a combination of an extended- Diseases and Disorders
dramatically raises the index of suspicion
for IE.
should be submitted for aerobic bacterial
spectrum penicillin (e.g., ampicillin with
dyspnea, cough) when congestive heart
culture.
failure (CHF) is present • Thoracic radiographs may show evidence of sulbactam 22 mg/kg IV q 8h), with a
fluoroquinolone (e.g., enrofloxacin 5 mg/
• Musculoskeletal abnormalities (e.g., lameness, CHF. kg IV q12h) or aminoglycoside (e.g., ami-
joint pain/stiffness) • Echocardiography may show an indepen- kacin). Amikacin may be preferable against
• Neurologic abnormalities (e.g., ataxia) dently oscillating mass associated with a heart Bartonella, but requires monitoring for
valve or adjacent structures; independently nephrotoxicity.
Etiology and Pathophysiology oscillating means that movements of the mass • Treatment of CHF if indicated (p. 408).
• The left-sided heart valves (aortic and/or are distinct and different from those of the • Anticoagulation does not appear to diminish
mitral) are affected most commonly in canine valve. Valve thickening from myxomatous/ the risk of bacterial embolization in humans
and feline IE. degenerative valvular disease can complicate and should be considered on a case-by-case
• Staphylococcus spp, Streptococcus spp, and echocardiographic interpretation. Some basis.
Escherichia coli are the most common isolates. animals have mural endocarditis without
Less commonly isolated pathogens include valvular involvement. Chronic Treatment
Pseudomonas, Proteus, Erysipelothrix, Entero- • Oral antibiotic therapy is generally continued
bacter, Pasteurella, and Corynebacterium. Advanced or Confirmatory Testing for 6-10 weeks and is based on culture
• Bartonella spp is a common cause of culture- • Three separate blood samples (5-10 mL each, and sensitivity results. In culture-negative
negative IE and appears to have tropism for patient size permitting), obtained aseptically cases, empirical oral therapy may include an
the aortic valve. by separate venipunctures at least 30-60 extended-spectrum penicillin (e.g., amoxicil-
• Anaerobic bacteria (e.g., Bacteroides) are minutes apart, should be submitted for lin with clavulanic acid 14 mg/kg PO q 12h),
uncommon. aerobic and anaerobic culture. fluoroquinolone (e.g., enrofloxacin 10 mg/kg
○ In acutely ill patients, three blood cultures PO q 24h) and doxycycline 5 mg/kg PO q
DIAGNOSIS 5-10 minutes apart are adequate. 12h. Repeat blood and urine cultures (and
○ Common causes of culture-negative IE are potentially 16S PCR) are ideal after starting
Diagnostic Overview previous antibiotic therapy and infection antibiotic therapy and again 1-2 weeks after
The diagnosis of IE is based on a constellation of by fastidious microorganisms. stopping antibiotics. Long-term therapy may
clinical, microbiologic, and echocardiographic • Identification of Bartonella spp typically be warranted in dogs with recurrent clinical
findings. The modified Duke criteria, which rep- requires PCR and culture using BAPGM. and/or persistent diagnostic abnormalities.
resent the cornerstone of diagnosis of human IE, ○ Bartonella serologic testing is useful to • Repeat echocardiograms to monitor the size/
have been adapted for veterinary use. Definitive identify antibody titers. appearance of vegetative lesion(s), severity of
IE is based on the presence of 2 major criteria • PCR amplification of 16S ribosomal bacterial valvular regurgitation, and extent of cardiac
or histopathologic confirmation. Possible IE is DNA used in conjunction with standard chamber dilation.
based on positive echocardiographic findings blood cultures increases the likelihood of • Treatment of chronic CHF if indicated
and 1 minor criterion, 1 major and 3 minor bacterial isolation. (p. 409).
criteria, or 5 minor criteria. The following • An electrocardiogram to identify any
criteria have been suggested for the diagnosis arrhythmia or conduction disturbance Possible Complications
of IE in dogs: (e.g., atrioventricular block), increasing the • CHF
• Major criteria: positive echocardiogram suspicion of perivalvular extension • Kidney injury (glomerulonephritis/protein-
(vegetative/oscillating lesion; erosive lesion; • Arthrocentesis (p. 1059) with joint fluid losing nephropathy, chronic kidney disease,
valve/mural abscess), new valvular insuf- analysis and culture in dogs exhibiting or both) and/or neurologic complications,
ficiency and/or aortic insufficiency, positive lameness secondary to embolic events and organ
blood culture (≥ 2 positive blood cultures iso- • Urine protein/creatinine (UPC) ratio in dogs (various) infarction
lating a typical organism or > 3 positive blood with proteinuria • Immune-mediated disease (e.g., glomerulo-
cultures with common skin contaminant) nephritis, polyarthritis)
• Minor criteria: fever, medium-sized to large TREATMENT • Sudden death, due to malignant arrhythmia
dog (>15 kg), SAS, thromboembolic disease, and/or infarction caused by embolization
immune-mediated disease (e.g., polyarthritis; Treatment Overview
glomerulonephritis), positive blood culture • Provide effective antibiotic therapy to PROGNOSIS & OUTCOME
not meeting major criteria, Bartonella titer or minimize valve damage.
positive PCR using BAPGM (i.e., Bartonella • Manage complications (e.g., CHF, throm- • Overall prognosis is guarded to grave due
alpha-Proteobacteria growth medium; Galaxy boembolism, polyarthritis). to the possibilities of embolic complications
Diagnostics, Morrisville, NC) • Surgical valve repair or replacement, con- and CHF. Long-term survival is possible in
sidered in human IE cases, is not practical the absence of CHF or severe neurologic
Differential Diagnosis in veterinary medicine. complications.
• Other systemic illness with nonspecific • CHF (pulmonary edema) is common,
complaints (e.g., fever, inappetence, weight Acute General Treatment resulting from volume overload caused by
loss, lameness) • Hospitalization and aggressive treatment with severe aortic insufficiency and/or severe mitral
• IE should be considered in any patient with parenteral antibiotics for 1-2 weeks is ideal regurgitation.
fever of unknown origin, especially in the after blood cultures are obtained. Antibiotic • Prognosis appears to vary, depending on the
presence of a heart murmur. therapy can be completed on an outpatient valve affected; aortic valve IE is often associ-
basis using oral antibiotics. ated with a grave prognosis (days to weeks,
Initial Database • Antibiotic selection should be based on especially grave in the presence of CHF or
• CBC and serum biochemical changes are not results of blood culture and susceptibility severe neurologic signs); longer survival is
specific. Anemia, leukocytosis (neutrophilia profile if possible. Pending culture results more typical of mitral valve IE as long as

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