Page 89 - Feline Cardiology

Chapter 10: Congenital Heart Malformations 87

Gross Pathology the morphology of the tricuspid valve should be normal
Tricuspid valve dysplasia is characterized by long, thick- in a cat with ARVC.
ened septal valve leaflets, which can be focal or
diffuse (Liu and Tilley 1976). The leaflets may adhere Diagnostic Testing
directly to the septum with absent or short, abnormal Electrocardiography
chordae tendinae. The papillary muscles may be hyper- Cats with tricuspid valve dysplasia may have a normal
trophied and attach directly to the valve leaflet (Liu sinus rhythm, a normal axis, and normal QRS morphol-
1977).
ogy. Alternatively, they may also have a splintered
(notched) QRS or evidence of right ventricular enlarge-
Signalment
ment (with a right axis shift of >160° and prominent S Congenital Heart Disease
There are no known breed predispositions. The breeds waves in leads I, II, III and aVF) (Liu and Tilley 1976;
reported in the literature include the domestic shorthair, Kornreich and Moïse 1997). Occasional atrial or ven-
Siamese, Birman, Persian, and Chartreux (Lord 1968; tricular premature beats have been observed (Chetboul
Liu and Tilley 1976, Fossum et al. 1994; Kornreich and et al. 2004).
Moïse 1997; Chetboul et al. 2004).

Radiography
History and Chief Complaint
Depending on the severity of the defect and the age
There is a spectrum of clinical presentations. Some
kittens or even adult cats are diagnosed at the time of a of the cat, the radiographs may be normal or may dem-
routine evaluation when a heart murmur is detected and onstrate signs of right-sided or generalized cardiomeg-
a thorough evaluation is performed. One cat presented aly (Chetboul et al. 2004). A dilated caudal vena cava
with exercise-induced tachypnea and two have been and pleural effusion suggest right heart failure (Figure
reported to present for syncope (Chetboul et al. 2004). 10.1).
Some cats are only diagnosed when they have progressed
to congestive heart failure and present with tachypnea Echocardiography
and dyspnea (Liu 1977). Two-dimensional echocardiography should identify the
abnormal, thickened appearance and movement of the
Physical Examination tricuspid valve and its abnormal attachment to the pap-
Cats with tricuspid valve malformation would be illary muscles or wall of the ventricle. Right atrial and
expected to have a holosystolic murmur over the 3rd– ventricular dilation can be observed as well. In milder
5th intercostal spaces on the right thorax. However, in cases, only a small amount of tricuspid regurgitation
some cases the degree of the abnormality may be so may be noted on color-flow Doppler examination as the
severe that right atrial and ventricular pressures seem to sole abnormality. Ebstein’s anomaly, a malformation of
equilibrate and the heart murmur may be very soft or the tricuspid valve where the basal attachment of the
even not detectable. Additionally some cats have mul- valve is more apically placed than normally, is another
tiple congenital cardiac malformations and have differential for the abnormal appearance of the tricuspid
murmurs that characterize their other defects. valve and may be considered as well. Ebstein’s malfor-
Cats with severe tricuspid valve dysplasia that mation is a specific type of tricuspid valve dysplasia, and
have progressed into heart failure may have distended it appears to be uncommon in the cat. Color-flow
jugular veins and tachypnea associated with pleural Doppler should indicate the presence of tricuspid valve
effusion. In rare cases, cyanosis can develop if a regurgitation in virtually all cases. Valvular stenosis
stenotic tricuspid valve or severe tricuspid regurgitation appears to be uncommon.
leads to elevated right atrial pressure and a patent A staging scheme for tricuspid valve dysplasia based
foramen ovale results in a right-to-left shunt at the on echocardiographic identification of tricuspid regur-
atrial level. gitation was suggested by Chetboul et al. (2004):

Differential Diagnosis • Stage 1: Tricuspid valve is structurally abnormal but
Cats with arrhythmogenic right ventricular cardiomy- the right atrium and right ventricle appear normal.
opathy (ARVC) can have a similar echocardiographic • Stage 2: Tricuspid valve is structurally abnormal and
appearance. However feline ARVC is generally observed right atrial dilation is present.
in older cats and should have a lesser degree of tricuspid • Stage 3: Tricuspid valve is structurally abnormal and
regurgitation noted on echocardiography. Additionally, both right atrium and ventricle are dilated.