Page 97 - Feline Cardiology

Chapter 10: Congenital Heart Malformations 95

Treatment Differential Diagnosis
Because the majority of cats with atrial septal defects The clinical, radiographic and echocardiographic find-
remain asymptomatic, treatment is not generally needed. ings of supravalvular mitral valve stenosis are very
Cats with large defects and volume overload may benefit similar to those of cor triatriatum sinister. The position
from angiotensin-converting enzyme inhibitors such as of the obstructing membrane relative to the left auricle
enalapril or benazepril. Large defects may result in the as noted on a two- dimensional echo, 4-chamber, right
development of heart failure and should be treated as parasternal view may help differentiate the two. Cor
described (see Chapter 19). triatriatum should be suspected if the left auricle is
located distal to the dividing membrane and supraval-
Prognosis vular stenosis should be suspected if the left auricle is Congenital Heart Disease
located proximal to the dividing membrane (Fine et al.
The prognosis is typically dependent on the size of the
defect. Cats with small atrial septal defects may remain 2002).
asymptomatic for life. Diagnostic Testing
Electrocardiography
COMMON AV CANAL (ENDOCARDIAL A right axis shift was observed in one case (Koie et al.
CUSHION DEFECT) 2000).
This developmental malformation is characterized by Radiography
absence of the lower/basal atrial septum, higher/dorsal Radiographs may indicate signs of left heart failure
ventricular septum, and malformation of the atrioven- including pulmonary venous congestion and pulmo-
tricular valves (mitral and tricuspid). nary edema.

Pathophysiology Echocardiography
The resultant abnormality leads to communication Echocardiography should identify a double chamber left
between all the chambers and results in heart failure atrium with a dilated proximal chamber (Figure 10.5).
usually by 1 year of age. The atrium should appear to be divided by a membrane
with a small communication between the two chambers.
The left auricle should be associated with the distal
COR TRIATRIATUM SINISTER chamber as noted on a two-dimensional, 4-chamber,
right parasternal view echocardiogram.
Cor triatriatum sinister is an uncommon defect in the
cat (Gordon et al. 1982; Wander et al. 1998; Koie et al. Treatment
2000; Heaney and Bulmer 2004). It is characterized by
the presence of a band of tissue that divides the left Kittens with cor triatriatum often present with clinical
atrium resulting in 2 left atrial chambers, which com- signs of congestive heart failure that should be addressed
municate through a small opening. One chamber as described (see Chapter 19). Surgical correction of cor
receives the pulmonary venous flow and the second
chamber communicates with the mitral valve.

Pathophysiology
Because of the small communication between the two,
obstruction of blood flow occurs between the two cham-
bers. The pressure in the proximal chamber becomes
elevated, the chamber dilates, and increased pressure is
reflected to the pulmonary veins. Left-sided heart failure
usually results.

Figure 10.5. Right-sided long-axis 4-chamber echocardio-
Physical Examination
graphic view from a cat with cor triatriatum sinister. Note the
A heart murmur is typically detected on the left side. double chamber left atrium (LA in 2 locations, separated by the
Both systolic and diastolic murmurs have been reported partitioning membrane [arrow]), with a dilated proximal chamber.
(Wander 1998; Heaney and Bulmer 2004). LV = left ventricle; RA = right atrium; RV = right ventricle.