Page 158 - Problem-Based Feline Medicine

150 PART 3 CAT WITH SIGNS OF HEART DISEASE

The murmur is usually due to the pulmonic stenosis and Cardiac catheterization findings
best heard at the left heart base. It is an ejecti on systolic
Selective angiography of the right ventricle will show:
murmur, which varies in intensity during systole because
● Right ventricular hypertrophy.
of the crescendo and decrescendo character.
● Large VSD.
Characterization of the ejection murmur may be diffi- ● Pulmonary valve stenosis and post-stenotic dilata-
cult in a cat because of the fast heart rate. tion of the main pulmonary artery.
● Overriding aorta.
Diagnosis Cardiac catheterization demonstrates equalization of
right ventricular and left ventricular pressures.
Radiographic findings
Pulmonary artery pressures are normal.
Normal cardiac size or right ventricular enlargement is
found.
Differential diagnosis
Dilated main pulmonary artery (post-stenotic dilata-
tion) is seen as a bulge in the left cranio-lateral part of Pulmonary stenosis.
the cardiac silhouette in the ventro-dorsal view or ● Cyanosis or brick-red mucus membranes are not
dorso-ventral view. seen with pulmonic stenosis.
● The murmur of pulmonic stenosis may be similar to
Under-perfused pulmonary circulation is seen as
the murmur heard in tetralogy of Fallot.
hypovascular lung fields characterized by hyperinflated
lungs and a decreased peripheral pulmonary vascula- Right to left PDA.
ture. ● In many cases, no murmur is heard although cyanosis
and exercise intolerance are usually present.
Electrocardiographic findings ● Cyanosis of the right-to-left PDA is usually periph-
Tachycardia is frequently seen with a heart rate greater eral and localized to the caudal portion of the body.
than 220 bpm.
Cardiomyopathies.
Right axis deviation is seen between −60 and −180 ● Cyanosis is only present in cases of severe pul-
degrees in the frontal plane. monary edema.
● The murmur is usually not as loud and may vary in
Deep S waves are seen on leads II, aVF and III.
intensity.
Echocardiographic findings
A large perimembranous ventral septal defect is seen Treatment
below an overriding aorta.
Medical therapy consists of periodic phlebotomy to
Pulmonary valve stenosis is present. Most cases have control clinical signs.
pulmonary artery hypoplasia and a dysplastic pulmonic ● Blood of volume removed = [BW (kg) × 0.08] × 1000
valve. ml/kg × Actual Hct.–Desired Hct./ – Actual Hct.
● Repeat PCV in 2 hours. The goal is to decrease PCV
Doppler study of the flow across the VSD will deter-
to ~60%. CAUTION–removing too much red cell
mine the direction of shunting of blood. Most fre-
mass may render the patient symptomatic at rest.
quently, there is right to left shunting.
Avoid heavy playing and keep confined within the
Doppler study across the pulmonary valve will deter-
household.
mine the degree of stenosis. Velocities of blood flow
obtained by continuous wave Doppler above 2.0 m/s Use beta-blockers if the heart rate is greater than 200
are diagnostic of stenosis. Usually the degree of steno- bpm at rest.
sis is severe (Vmax > 5.0 m/s). ● Propranolol – 0.5–1 mg/kg q 8 h OR
● Atenolol 6.25–12.5 mg/cat q 12 h.
Saline contrast studies may be helpful in identifying the
direction of shunting. Surgical options are available but rarely performed.