Page 101 - Feline Cardiology

Chapter 10: Congenital Heart Malformations 99

Prognosis shunting across the ventricular septal defect (Fruganti et
The prognosis may depend on the severity of the defect, al. 2004).
but some cats appear to do quite well and remain asymp-
tomatic or with only mild symptoms for some time. Additional Testing
Polycythemia is expected when substantial right-to-left
TETRALOGY OF FALLOT shunting of blood is present.

Tetralogy of Fallot is an uncommon congenital defect in Treatment
the cat. It is characterized by a ventricular septal defect, Surgical therapy including the development of a shunt
obstruction of the right ventricular outflow tract (pul- from the systemic to the pulmonary system has been
monic stenosis), an overriding (dextropositioned) aorta successfully performed but is challenging in a cat (Miller Congenital Heart Disease
(arising from both ventricles), and secondary right ven- et al. 1985). Medical therapy with a beta blocker, par-
tricular hypertrophy. Shunting of blood through the ticularly propranolol (2.5–5 mg/cat PO q 8h; begin low
ventricular septal defect is typically right to left or mixed and titrate up to desired effect of preventing tachycar-
due to the obstruction of the pulmonary artery and dia) may be helpful. In this case, propranol may be more
elevated right ventricular pressures.
helpful than atenolol, which is cardioselective.
Phlebotomy may be needed periodically to try to main-
History and Chief Complaint
tain the PCV below 68% if polycythemia occurs.
Affected cats have been reported to be small and possibly
stunted. They may present with dyspnea, exercise intol- Prognosis
erance, cyanosis, or syncope. Tetralogy of Fallot generally carries a poor prognosis,
though the specific prognosis depends on the combina-
Physical Examination
tion of size of ventricular septal defect, degree of pul-
Cyanosis associated with a right-to-left shunting ven- monic stenosis, and degree of dextroposition of the
tricular septal defect is generally noted, but not always. aorta. Therefore, the diagnosis of tetralogy of Fallot does
A systolic murmur consistent with pulmonic stenosis not by itself indicate a definitive prognosis; the extent of
may be ausculted at the left base of the heart, but it may the primary lesions, and their effects (overt clinical
radiate generally and be heard over the right thorax signs, polycythemia, etc.) must be considered in order
as well. to provide an accurate prognosis.

Differential Diagnosis REFERENCES
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