Page 98 - Feline Cardiology

96 Section C: Congenital Heart Disease

triatriatum has been reported but is challenging (Wander Radiography
et al. 1998). Right-sided enlargement is a common finding. Pleural
effusion may be observed.
Prognosis
The prognosis for cor triatriatium is generally poor, Echocardiography
with kittens generally succumbing to the signs of A fibromuscular bundle should be noted crossing the
Congenital Heart Disease DOUBLE CHAMBER RIGHT VENTRICLE level. Right ventricle hypertrophy should be noted prox-
congestive heart failure. Pulmonary hypertension may
right ventricle, most commonly at the midventricular
develop.
imal to the lesion but not below it. The pulmonic valve
should appear normal. Doppler echocardiography
should reveal an increased pressure gradient across the
Double chamber right ventricle is a congenital defect
fibromuscular band (high velocity of blood flow across
characterized by the presence of anomalous muscle
bundles that spread from the septal wall of the right
the pulmonic valve should be normal. In some cases a
ventricle to the parietal wall, dividing the right ventricle. the communicating aperture in the band). Flow across
A breed predisposition has not been noted. One report small perimembranous ventricular septal defect was
noted as a concurrent finding (Koffas et al. 2007).
noted it in 4 domestic shorthairs, 1 domestic longhair,
and 1 each Birman, Bengal, Maine coon, and Manx
(Koffas et al. 2007). Treatment
Treatment for heart failure, if present, should be initi-
Pathophysiology ated as described (see Chapter 19). A beta blocker such
as atenolol (6.25–12.5 mg PO q 12 hours) might be ben-
The right ventricle is divided into two smaller compart-
ments by the muscle bundles. The proximal compart- eficial if heart failure is not present. Surgical treatment
ment is exposed to higher pressure due to the obstruction with a patch graft was successfully performed in one case
caused by the muscle bundles and may have right ven- (Koffas et al. 2007). Balloon valvuloplasty was attempted
tricular hypertrophy. The distal chamber has normal in one case, not successfully, likely due to the fibrous
pressures. bundles not being responsive to valvuloplasty (i.e., they
stretch and deform rather than breaking or tearing)
(MacLean et al. 2002).
History and Chief Complaint
Reported clinical signs are fairly nonspecific and have Prognosis
included lethargy, exercise intolerance, and chylothorax,
but some cats remain asymptomatic (MacLean et al. Many cats remain asymptomatic for years, but others
2002; Koffas et al. 2007). may progress to the development of heart failure, with
chylothorax a possible outcome.
Physical Examination
A systolic heart murmur is most commonly heard on PATENT DUCTUS ARTERIOSUS
the left hemithorax, but it may be loudest on the right. Patent ductus arteriosus (PDA) is an uncommon defect
Progression of the disease can include the development in the cat. A patent ductus arteriosus occurs when the
of right heart failure, so jugular venous pulses may be embryologic ductus that allows shunting of blood
observed. between the pulmonary artery and the ascending aorta
fails to close (Figure 10.6).
Differential Diagnosis
Because pulmonic stenosis can also lead to the develop- Etiology and Pathophysiology
ment of right ventricular hypertrophy, it should be Etiology
considered.
Although the patent ductus arteriosus is well known for
being a familial trait in the dog, heritability has not been
Diagnostic Testing
demonstrated in the cat.
Electrocardiography
A sinus rhythm is expected, but a right axis shift or an Pathophysiology
arrhythmia could be observed. Atrial tachycardia has As long as the ductus is patent, blood will shunt from
been noted as well. the descending aorta to the pulmonary artery since the