Page 189 - Feline Cardiology

Chapter 14: Arrhythmogenic Right Ventricular Cardiomyopathy 191

septal motion may be observed. Aneurysmal bulges in ered including treatment with aspirin or clopidogrel as
the apical or subtricuspid region are uncommon but are described (see Chapter 20).
characteristic of ARVC. Mild myocardial dysfunction of
the left ventricle may be observed, but function is more
commonly within normal limits. COMPLICATIONS AND MONITORING
The Doppler echocardiogram often identifies mild After the initial diagnosis is made, reevaluation and
tricuspid valve regurgitation due to the dilated right control of treatment will be based on control of respira-
ventricle and tricuspid valve annulus. As mentioned tory rate and heart rate that can be determined by physi-
above, a differential diagnosis for feline ARVC would be cal examination, radiographs, and electrocardiogram. A
congenital tricuspid valve dysplasia, which should have renal profile to monitor BUN, creatinine, and electro-
higher velocity tricuspid valve regurgitation as well as lytes is also helpful to monitor for development of azo-
abnormal valve morphology. temia. Recheck echocardiography is needed only if the
case seems to be progressing unusually rapidly or in an Cardiomyopathies
TREATMENT unusual fashion. It should be remembered that a trip to
the veterinary hospital for reevaluation is almost always
There are no specific treatments for arrhythmogenic associated with increased stress for a cat and may in
right ventricular cardiomyopathy in the cat. some cases result in a well-controlled cat suddenly
Treatment should include medications as needed for decompensating. Therefore the benefits and indications
the symptoms associated with congestive heart failure if for a hospital revaluation should be carefully weighed
it is present. This might include furosemide and an ACE with possible risks and it should not be recommended
inhibitor as described in Chapter 19. unless truly medically indicated. Additionally, the
Thoracocentesis and/or abdominocentesis should be reevaluation appointment should be done as efficiently
performed (see Chapter 3) if pleural effusion or ascites and as calmly as possible to minimize stress.
is present and is negatively impacting respiration. Congestive heart failure, right or biventricular, is a
If clinical signs are present that are thought to be common complication of this disease. Owners should
associated with the ventricular tachycardia (syncope, be instructed to monitor the respiratory rate at home in
exercise intolerance, lethargy) or if the tachycardia a resting state. A target resting respiratory rate for a cat
is sustained, an antiarrhythmic like sotalol should should be less than 16 breaths per minute. If the respira-
be considered. Sotalol may be prescribed at 1–2 mg/kg tory rate is maintained in a low range and the cat is
orally q 12 hours. The efficacy of this drug for feline eating and appears comfortable, a recheck may not yet
ARVC has not been extensively studied. However, be needed. If an owner detects a persistently elevated
sotalol has been used for treatment of the arrhythmias respiratory rate it may be a sign of developing pleural
associated with ARVC in both dogs and human beings effusion and indicates a need for a reevaluation with
(Meurs et al. 2002; Marcus et al. 2009). The sotalol thoracic radiographs.
caplets come in 80 mg, 120 mg, and 240 mg but it is pos-
sible to have them compounded for accurate dosing in OUTCOME AND PROGNOSIS
the cat.
If atrial fibrillation or an atrial tachycardia is observed, Generally, feline ARVC carries a grave prognosis. Many
antiarrhythmics such as digoxin or diltiazem may be cats are euthanized for right heart failure within 4
indicated to slow the heart rate (ventricular response months of clinical onset (Fox et al. 2000; Harvey et al.
rate) (see Chapter 18) with an ideal target heart rate of 2005). Cats are also at risk of thromboembolism.
140–180 on medication.
If the right ventricle is very dilated and ventricular REFERENCES
dysfunction is suspected, pimobendan, a positive ino-
trope, may be useful at a dose of 1.25 mg–1.5 mg/cat PO Boldface font indicates key references.
Basso C, Fox PR, Meurs KM, et al. Arrhythmogenic right ventricular
q 12 hours, although its use in cats is not yet approved cardiomyopathy causing sudden cardiac death in Boxer dogs: New
in the United States. Therefore, use of this drug in cats animal model of human disease. Circulation 2004;109:1180–1185.
should be supported by client understanding and Fox PR. Feline cardiomyopathy. In Fox PR, Sisson DD, Moïse, NS, eds.
consent for off-label use. Textbook of Canine and Feline Cardiology, 2nd ed. Philadelphia,
WB Saunders, 1999, pp. 621–678.
Right atrial enlargement could lead to the develop- Fox PR, Maron BJ, Basso C, et al. Spontaneously occurring arrhyth-
ment of an atrial thrombus, and prevention of possible mogenic right ventricular cardiomyopathy in the domestic cat.
thromboembolic complications should also be consid- Circulation 2000;102:1863–1870.