Page 196 - Feline Cardiology

Chapter 15: Acquired Valvular Disease 199

Diagnosis in cases of IE depends on documentation diographic and clinical findings resulted in the best
of markedly elevated serum antibodies to Bartonella and sensitivity and specificity, and this scheme has been
demonstration of Bartonella antigens using polymerase slightly modified for the veterinary patient (Miller and
chain reaction testing for Bartonella spp DNA (often a Sisson 1999). A diagnosis of IE is likely in an individual
postmortem finding on valve tissue). Definitive diagno- patient when two major criteria, one major and three
sis is difficult because many cats are carriers and are minor, or five minor criteria are met (Tables 15.1, 15.2).
therefore seropositive. Because Bartonellae are extremely Serial echocardiographic examinations are sometimes
fastidious intracellular bacteria, they are rarely cultured helpful because the valve can appear structurally normal
from blood or body tissues even using specialized culture in the early stages of disease. Over time, vegetations
medium and long incubation periods. With endocardi- often develop into an irregular and pedunculated mass
tis, identification of the causative organism is often chal- arising from the tip of the valve leaflet, and the hemo-
lenging, whatever the etiologic agent. Although multiple dynamic consequences (aortic and/or mitral regurgita-
sets of blood cultures (3 samples over 3 hours) are rec- tion) can be readily appreciated. Aortic or mitral
ommended to evaluate patients in whom IE is suspected, stenosis secondary to large, space-occupying vegeta-
the small body size of cats means volumes of blood tions, rarely occur in feline IE cases. In cats, the vegeta-
withdrawn should be considered carefully. Most blood tion will often mineralize, making it appear hyperechoic Misc. Heart Diseases
culture media bottles require 5–15 ml for each sample, on ultrasound.
and the effect on a debilitated patient must be consid- Therapy of IE is directed at controlling sepsis and
ered when planning this diagnostic test. A urine culture management of cardiac dysfunction secondary to valvu-
is always indicated and may identify the causative organ- lar insufficiency and/or stenosis. Congestive heart failure
ism. If the patient is already receiving antibiotic therapy, is an important sequela of this disease in cats. More than
samples for cultures should be drawn when antibiotic half of the cases in Malik’s series presented for veterinary
blood levels are at trough levels (Miller and Sisson 1999). care secondary to signs referable to CHF rather than
Retrospective human studies demonstrated that signs of sepsis. See Chapter 19 for discussion of conges-
using a combination of laboratory data and echocar- tive heart failure therapy. Antimicrobial therapy is most

Table 15.1. Major vs minor criteria for diagnosis of infectious endocarditis

Major Criteria Minor Criteria

Two separate, positive blood cultures with organisms likely Predisposing factor (subaortic stenosis in dogs, unknown
to cause IE (Staph spp, Strep spp, Corynebacterium spp, whether factor in cats; long-term in-dwelling catheter)
Erysipelothrix rhusiopathiae [typically serovar 7],
Pseudomonas aeruginosa, Pasteurella spp)
Fever (historical or at presentation)

Three or more separate, positive blood cultures with
Thromboembolic disease (pulmonary, central nervous
common skin contaminants
system, or arterial emboli)
Positive echocardiographic findings for IE (oscillating
Immunologic disease (glomerulonephritis, vasculitis,
intracardiac mass on valve or valve apparatus in the absence
of alternative explanation, i.e., thrombus); erosive lesion polyarthropathy)

Microbiologic evidence (positive blood culture[s]) that
New valvular regurgitation
does not meet “major criteria”

Echocardiographic evidence (findings consistent with IE,
but which do not meet “major criteria”)

Identification of Bartonella antigens using polymerase
chain reaction testing on bacterial isolates or valve tissue

Modified from Miller and Sisson 1999, p. 572.