Page 153 - Problem-Based Feline Medicine

9 – THE CAT WITH ABNORMAL HEART SOUNDS AND/OR AN ENLARGED HEART 145

It is important to note that due to the thickness of If the patient is in congestive heart failure, refer to
the septum in a normal heart, many times there is hypertrophic cardiomyopathy section (page 130) for
the illusion of an echo drop out. Multiple views must treatment details.
be obtained to reach a diagnosis.
Doppler confirmation of left-to-right shunting is doc- Prognosis
umented across the atrial septal defect.
Prognosis is good in most cases, but it depends on the
Doppler study may show variable degrees of mitral degree of shunt fraction, which is dependent on the degree
regurgitation. of mitral regurgitation present.
Relative pulmonic stenosis (blood flow velocity > 2.0 Many cats have a normal lifespan.
m/s) secondary to increased volume of blood may be
seen with significant shunt fractions.
In severe cases, biatrial and bi-ventricular enlargement MITRAL VALVE DYSPLASIA/STENOSIS
can be seen.
Classical signs
Cardiac catheterization
● Systolic and/or diastolic murmur is heard
A catheter can be passed across the interatrial sep- over the left apex.
tum into the left atria and ventricle. ● Dyspnea.
An increase greater than 5% in oxygen saturation at the ● Thromboembolic disease
level of the right atrium when compared with blood
from the caudal vena cava is indicative of an atrial sep- Pathogenesis
tal defect with left-to-right shunting.
Congenital mitral valve malformation will result in poor
Angiographic contrast study from the left atria will
coaptation of its leaflets and secondary regurgitation.
show shunting of blood into the right heart with opaci-
fication of the right atria and ventricle. In some cases, the mitral valve is thick and misshapen
with restricted motility during diastole, causing impaired
Differential diagnosis blood flow from the left atrium to the left ventricle.
Cardiomyopathy is uncommon in young cats. In some cases, more than two leaflets may be present.
Cardiomyopathy murmurs are usually not as loud. Most commonly, the anterior leaflet may be subdivided
Cardiomyopathy murmurs may sound different with and it is called a cleft mitral valve.
serial auscultations.
Clinical signs
Ventricular septal defects usually have a louder murmur
on the right sternal border and the character is harsher. A heart murmur is heard loudest over the left heart apex
and is present from a young age.
Mitral valve dysplasia occurs with a murmur louder at
the apex, in some cases a diastolic murmur may be pres- Dyspnea or respiratory distress occur if congestive
ent if there is significant mitral stenosis. heart failure is present.
Pulmonic or aortic stenosis present with louder and Signs of increased respiratory rate, dyspnea or col-
harsher murmurs than atrial septal defects. lapse may be seen while playing.

Lameness, paralysis or paresis may result from sys-
Treatment
temic thromboembolism.
Many cases are asymptomatic and there is no need for
Atrial arrhythmias may be present if there is severe left
therapy.
atrial enlargement. Atrial premature contractions,
Definitive therapy requires surgical repair, which is paroxysmal atrial tachycardia or atrial fibrillation can
very difficult to accomplish in veterinary medicine. be seen.