Page 194 - Feline Cardiology

Chapter 15: Acquired Valvular Disease 197

RV RV
RA

LV
LV
LA

Figure 15.2. Right parasternal long-axis color-flow Doppler Figure 15.4. Right parasternal long-axis 4-chamber echocardio-
echocardiogram of the mitral valve. Note that the aliased color- gram from the same cat as the previous images. Note the en- Misc. Heart Diseases
flow pattern representing the high-velocity jet of mitral regurgita- larged left atrium (LA) and right atrium (RA) and thickening of the
tion is filling the left atrium. This echocardiogram was obtained mitral valve. RV = right ventricle; LV = left ventricle.
from the same cat as the radiographs in Figure 15.1. LV = left
ventricle; RV = right ventricle.
valve. Sometimes with mitral dysplasia the anterior
leaflet appears elongated and misshapen, and papillary
muscles may be abnormal in shape and position in the
left ventricle. Another common cause of mitral regurgi-
tation is functional, secondary mitral regurgitation due
to other cardiac diseases such as dilated cardiomyopathy,
RA unclassified cardiomyopathy, or left-to–right shunts,
Ao which lead to left ventricular enlargement. Secondary, or
functional mitral regurgitation, is typically mild or mod-
erate and often is symmetrical and centrally arising (in
LA the valve orifice), with a normal mitral valve structure.

INFECTIVE ENDOCARDITIS

Infectious endocarditis (IE) is extremely rare in cats with
an incidence of 0.006 to 0.018% of cats presented for exam-
Figure 15.3. Right parasternal short-axis echocardiogram of the ination in one retrospective report (Sisson 1994). The
heart base. Note the left atrial (LA) enlargement. The right atrium mitral and/or aortic valves are most commonly affected,
(RA) also appears enlarged. This echocardigram was obtained which is similar to dogs. Several factors are important in
from the same cat as the radiographs in Figure 15.1. Ao = aorta. the pathogenesis of infective valvular endocarditis:

• Endothelial damage
placement of the anterior mitral leaflet in cats with SAM, • Activation of clotting factors
where it approaches or touches the interventricular • Bacteremia and colonization of a noninfective throm-
septum during systole. On color-flow Doppler interro- bus on the valve surface
gation, SAM produces two turbulent jets: one ascending
into the aorta as a result of the left ventricular outflow Healthy endothelium is not particularly receptive to bac-
tract obstruction and the other in the left atrium as a terial attachment. However, when it is damaged, the
result of mitral regurgitation. The jets arise from the development of platelet-fibrin aggregates provides a
same point where the valve leaflet causes the obstruction. susceptible nidus for bacterial colonization. Valvular
Mitral valve dysplasia is the most common cause of endothelium is rich in fibronectin, a glycoprotein pro-
mitral regurgitation in kittens or juvenile cats. The mitral duced following endothelial injury. Many pathogenic
valve typically has characteristic morphologic abnor- bacteria associated with IE have surface receptors for
malities including short, thick chordae tendinae, which fibronectin (Peddle and Sleeper 2007), and Staphylococcus
may tether the abnormally shaped thickened mitral aureus, which possesses fibronectin receptors, has been