Page 92 - Feline Cardiology

90 Section C: Congenital Heart Disease

stenosis). Progression to left heart failure is also a likely Physical Examination
negative prognostic indicator, and it appears to be the Cats with primary mitral valve stenosis should have a
most likely outcome of cats with this defect if the cat low-frequency diastolic murmur or diastolic rumble
experiences clinical decompensation. caused by low-velocity turbulence of blood entering the

left ventricle through the stenotic valve. This type of
MITRAL VALVE STENOSIS murmur is often very difficult to hear due to its soft
Congenital Heart Disease valve or subvalvular or supravalvular area, is described monary edema, makes a soft diastolic murmur virtually
intensity, low frequency, and—in the cat—high heart
Mitral valve stenosis, a narrowed annulus of the mitral
rate; concurrent pericardial or pleural effusion, or pul-
much less commonly than mitral valve dysplasia in
impossible to hear. It was not reported in any of the 6
the cat. Valvular or supravalvular mitral valve stenosis
feline cases. However, a left apical systolic murmur may
has been reported in at least 6 cats (Fine et al. 2002;
be ausculted (3 of 5 cats in which auscultation was
Stamoulis and Fox 1993; Matsuu et al. 2007; Takemura
described) (Stamoulis and Fox 1993; Fine et al. 2002) if
et al. 2003).
mitral regurgitation is present (n = 4 of 5 cats in which
color Doppler echocardiographic studies were reported)
Etiology and Pathophysiology (Stamoulis and Fox 1993; Fine et al. 2002; Matsuu et al.
Etiology 2007).
Mitral valve stenosis is an uncommon feline malforma-
tion. The small number of reported cases has prevented Differential Diagnosis
any studies of etiology. Supravalvular mitral valve stenosis can be confused with
cor triatriatum sinister (see below). Differentiation is
Pathophysiology based on the level of the obstruction. In supravalvular
The stenotic area at the supravalvular, valve, or subval- mitral stenosis, the left auricle is proximal to the
vular region impedes normal diastolic (filling) function, obstructing membrane, but with cor triatriatum sinister
resulting in elevated left atrial pressures, increased pul- the left auricle is distal to the dividing membrane.
monary venous congestion, and pulmonary edema. The
valve may be insufficient as well as stenotic. Diagnostic Testing
Electrocardiography
Signalment
The electrocardiogram of a cat with mitral valve stenosis
Reported cases have occurred only in adult cats, would be expected to be similar to those of mitral valve
ranging from 3 years of age (Fine et al. 2002) to 16 dysplasia and could include evidence of left atrial
years of age (Stamoulis and Fox 1993) (median = 9 enlargement defined by a widened P wave (>0.04
years of age), leading to speculation that mitral valve seconds) and/or left ventricular enlargement defined by
stenosis may be an acquired, rather than congenital a tall R wave (>0.9 mV).
disorder in the cat (Takemura et al. 2003) as it often
is in humans. Alternatively, since the auscultatory find- Radiography
ings of mitral valve stenosis may be subtle or nonex-
istent (see below), the defect may simply escape notice Depending on the severity of the defect and the age
until congestive heart failure occurs (Stamoulis and of the cat, the radiographs may be normal or may
Fox 1993). Four domestic shorthairs (3 male, 1 female) reveal left-sided (atrial or ventricular) or generalized
and 2 Siamese cats (1 male, 1 female), all neutered, cardiomegaly. Signs of heart failure with patchy
have been reported. pulmonary edema and pulmonary venous congestion
are expected when affected cats are dyspneic. In
History and Chief Complaint some cases, pulmonary artery congestion may be
observed as well, suggesting the development of pulmo-
The chief complaint for all 6 cats with mitral stenosis
was dyspnea and/or tachypnea referable to pulmonary nary hypertension.
edema, pleural effusion, or both. In 2 cats, signs of aortic
thromboembolism were also present. In a young kitten Echocardiography
or one with a mild malformation, it may be assumed Two-dimensional and M-mode echocardiography may
that overt clinical signs would not be apparent (Fine show abnormal movement of the mitral valve during
et al. 2002; Stamoulis and Fox 1993; Matsuu et al. 2007; diastole if the stenosis is at the valve level. Specifically,
Takemura et al. 2003). tethering of the valve leaflets and concordant movement