Page 99 - Feline Cardiology

Chapter 10: Congenital Heart Malformations 97

History and Chief Complaint
In one study, the most common clinical presentation
included abnormal respiration, exercise intolerance, and
AO
poor growth (Hitchcock et al. 2000).

Physical Examination
PA
Although the heart murmur of a patent ductus arterio-
sus is typically continuous, in about 1/3 of the feline
cases in one study, only the systolic component of the
murmur was heard (Hitchcock et al. 2000). In some Congenital Heart Disease
cases, the continuous murmur is heard best ventrally.
Hyperkinetic pulses were identified in about 1/3 of
feline cases.

Diagnostic Testing
Electrocardiography
Figure 10.6. Heart from a cat with a patent ductus arteriosus A normal sinus rhythm and normal axis may be
(PDA). The arrow indicates the patent ductus connecting the de- observed, but left ventricular chamber enlargement pat-
scending aorta (Ao) and the pulmonary artery (PA). Moderate terns may be observed.
right ventricular enlargement is also seen.

Radiography
The most commonly reported radiographic abnormal-
pressure in the aorta is naturally always higher ity is cardiomegaly. Left-sided enlargement would be
(120/80 mm Mg) than the pulmonary artery (25/12 mm expected, with pulmonary overcirculation also com-
HG). Shunting of blood occurs both though systole and monly expected. The cardiac apex may be displaced to
diastole and is, therefore, a continuous shunt. The shunt- the right.
ing of blood from the aorta to pulmonary artery results
in left-sided volume overload as the blood circulates Echocardiography
through pulmonary artery and veins, back to the left Echocardiography is needed to confirm the diagnosis.
atrium and ventricle, and through the aorta and pulmo- Doppler echocardiography should in the region of the
nary artery again. Left heart failure may develop. pulmonic valve and ductus should show continuous
Some cats develop elevated pulmonary artery pres- flow shunting into the pulmonary artery from the
sure, likely due to the impact of the increased blood ductus (Figure 10.7). It can be quite challenging to
volume on pulmonary vasculature (Eisenmenger’s phys- image the actual ductus in a cat, particularly a kitten.
iology), as described for ventricular septal defects. The Cats that develop pulmonary hypertension may show
elevated pulmonary pressures may become high enough signs of right ventricular hypertrophy.
to result in a reversal of the direction of the shunt, now
shunting from pulmonary artery to the descending
aorta. These patients may develop polycythemia and dif- Treatment
ferential cyanosis as the deoxygenated blood from the Because patients with patent ductus arteriosus may
pulmonary artery is shunted to the descending aorta. develop left heart failure and pulmonary hypertension,
Irreversible changes in the pulmonary vasculature may repair is almost always advised. Surgical ligation of the
develop. defect is most common, but transvenous embolization
with a detachable coil has also been reported in 2 cats
Signalment
(Schneider and Hildebrandt 2003; Summerfield and
Specific breed predispositions or genders with increased Holt 2005). Uncommonly an older cat may present with
predisposition have not been noted. a patent ductus arteriosus that was not diagnosed at a
The patent ductus arteriosus is an uncommon defect young age. In some cases, if the patent ductus arteriosus
in the cat; therefore, specific signalment prevalences is small with little volume overload, surgical correction
have not been defined. may not be needed.