Page 188 - Feline Cardiology

190 Section D: Cardiomyopathies

et al. 2000). No breed predisposition has been noted first-degree AV block, and third-degree AV block may
(Fox et al. 2000; Harvey et al. 2005). be observed alone or in combination (see Chapter
18).
HISTORY AND CHIEF COMPLAINT
Radiography
The majority of affected cats have presented for vague Right atrial and ventricular enlargements are almost
clinical signs, including lethargy and anorexia; addition- always observed, and findings consistent with right heart
ally, signs of right heart failure including dyspnea and failure (pleural effusion, caudal caval distention) are fre-
tachypnea may be observed. Syncope may be observed quently present.
but appears to be uncommon (Fox et al. 2000; Harvey Echocardiography
et al. 2005). Sudden death is possible. ARVC may be
Cardiomyopathies detected incidentally in cats not showing overt clinical Echocardiography is needed to confirm the diagnosis.
signs, but the majority of cases are identified due to
The significant right-sided lesions consist of right atrial
presentation related to overt clinical signs (Fox 1999;
and right ventricular enlargement and decreased right
Paige et al. 2009).
ventricular wall motion (Figures 14.1, 14.2). Paradoxical
PHYSICAL EXAMINATION

Physical examination findings are often consistent with
right heart failure including hepatosplenomegaly, abnor-
mal jugular distension and pulsation, and a soft holo-
systolic right apical murmur associated with tricuspid RV
valve regurgitation. In some cats, a murmur may not be
detected. Tachyarrhythmias may be ausculted.
LV
DIFFERENTIAL DIAGNOSIS
A differential diagnosis for ARVC is the congenital heart PI. Ef
defect tricuspid valve dysplasia (see Chapter 10). Arrhy-
thmogenic right ventricular cardiomyopathy is an adult
onset form of myocardial disease, so it should be recog-
nized by detection of a murmur or tachyarrhythmia in Figure 14.1. Short-axis echocardiogram of a cat with ARVC.
an adult cat. Because tricuspid valve dysplasia is a con- Note the right ventricular enlargement and presence of pleural
genital heart defect and is present at birth, one would effusion in the thorax. RV = right ventricle; LV = left ventricle;
expect that at least a soft systolic right apical murmur Pl.Ef = pleural effusion.
should be present at a very young age. However, some
cats with tricuspid valve dysplasia may have only a very
soft murmur that could be missed (see Chapter 1).
Echocardiography would be the best test to differentiate
the two diagnoses. Although both ARVC and tricuspid
valve dysplasia cause tricuspid valve regurgitation, it
would be expected to have higher velocity in tricuspid
valve dysplasia. Additionally tricuspid valve dysplasia RV
should have abnormal valve morphology and fairly
normal right ventricular systolic function in most cases.
LV
DIAGNOSTIC TESTING
PI. Ef
Electrocardiography
Arrhythmias are commonly observed in feline ARVC. Figure 14.2. M-mode echocardiogram of a cat with ARVC. Note
Ventricular premature complexes, ventricular tachycar- the right ventricular enlargement and presence of pleural effusion
dia, atrial fibrillation, atrial standstill, supraventricular in the thorax. RV = right ventricle; LV = left ventricle; Pl.Ef = pleu-
premature complexes, right bundle branch block, ral effusion.