Page 151 - Problem-Based Feline Medicine

9 – THE CAT WITH ABNORMAL HEART SOUNDS AND/OR AN ENLARGED HEART 143

A continuous murmur is located over the heart base in 71% A small amount of aortic insufficiency may be seen.
of the cases. The other 29% have systolic murmurs only.
Diagnosis
Bounding arterial pulses are commonly found.
Right to left shunt.
A strong precordial impulse is commonly found and
● These cases are rare.
results from the cardiomegaly.
● There is a history of a loud murmur that resolved or
Arrhythmias can be found in severe cases. is only diastolic now.
● A loud second heart sound, which may be split,
Faint diastolic murmur or no murmur is present in right
may be heard.
to left PDAs.
● Lethargy, dyspnea and/or collapse are common.
Polycythemia with PCV exceeding 65% may be found
in right to left PDA. Radiographic findings
Generalized cardiomegaly with a large main pulmonary
Concurrent cardiac defects are found in 29% of the
artery is seen.
cases.
Pulmonary over-circulation is not seen with a right to
Diagnosis
left shunt.
Left to right shunt:
Electrocardiographic findings
● Congenital continuous murmur is heard with
bounding arterial pulses. Right heart enlargement pattern (right axis deviation) is
seen.
Radiographic findings
Echocardiographic findings
Left atrial and ventricular enlargement can be seen.
Right ventricular hypertrophy is seen (RVIDd > 6 mm
Large pulmonary vessels suggesting over-circulation and RVFWd > 3 mm).
can be seen.
Left heart enlargement (LVIDd > 18mm) may also be
Enlarged main pulmonary artery and aortic arch can be present.
seen.
Doppler flow across PDA from right to left or bi-direc-
Pulmonary edema may be present in complicated cases. tional flow can be seen.

Electrocardiography Differential diagnosis
Left ventricular hypertrophy (R wave in lead II > 0.9 Aorticopulmonary window can only be differentiated
mV) is common. by echocardiographic study; continuous blood flow
Left atrial enlargement (P wave > 40 ms) can be seen. with shunting between the aorta and MPA is seen at the
level of the aortic root.
Tachycardia can be seen.
Truncus arteriosus can be differentiated by echocar-
Arrhythmias are uncommon. diography; a common large outlet for the left and right
ventricles is seen.
Echocardiographic findings
Pulmonary arteriovenous fistula will produce similar
Left heart enlargement (LVIDd > 18 mm), hyperkinetic
hemodynamic abnormalities as a left to right PDA but
left ventricular function (FS > 55%), enlarged main pul-
the flow within the main pulmonary artery is normal.
monary artery (MPA > 10 mm) and aortic arch are seen.
Doppler shows persistent flow of blood within the Treatment
main pulmonary artery through all phases of the car-
Surgery is curative for left to right PDA. The success
diac cycle.
rate of surgery is 85% when performed by an experi-
Mitral regurgitation may be present. enced surgeon.