Page 180 - Feline Cardiology

180 Section D: Cardiomyopathies

for rapid supraventricular tachyarrhythmias (atrial
E fibrillation, etc.) should be managed to ideally have a
+ heart rate of 140–160 beats per minute on medication
when examined at the hospital.

COMPLICATIONS AND MONITORING
A Because cats with RCM appear to be at an increased risk
of thromboembolic disease, owners should be advised
X
to observe for signs of sudden paralysis, most commonly
Cardiomyopathies Owners should monitor the respiratory rate at home in
of the hindlimbs, but sometimes of a forelimb.
Congestive heart failure is often a complication.
a resting state once a day if possible; ideally it should be
less than 30 breaths per minute. An increase in respira-

Figure 12.5. Transmitral flow velocities from a cat with restric- tory rate may be an indication of the development of
pulmonary edema or pleural effusion.
tive cardiomyopathy. Note the restrictive filling pattern with in- Once the initial diagnosis is made, reevaluation and
creased E wave and shortened A wave (high E:A ratio) (see Chap- adjustment of medications is typically directed at control
ters 7 and 11).
of the clinical signs of heart failure. Much of this can be
based upon history (owner’s record of daily respiratory
rate at home) physical examination, radiographs, and
enlargement and typically normal ventricular wall thick-
ness. A hyperechoic appearance to the endocardial blood pressure. A renal profile to monitor BUN, creati-
surface may be observed as well as moderately decreased nine, and electrolytes is also helpful to guide drug
systolic dysfunction. therapy. Rechecking echocardiography may be needed
Pathologic findings should include an increase in only if acute changes occur, such as sudden decompen-
heart weight, and biatrial dilation with normal wall sation, or acute development of signs suggestive of
thickness and an absence of other structural defects thromboembolism.
(ventricular septal defect, mitral valve dysplasia, etc.)
that could explain the changes. OUTCOME AND PROGNOSIS

TREATMENT Unfortunately, the long-term prognosis is generally
poor. Many cats succumb to heart failure or a thrombo-
There is no specific therapy for RCM. Treatment is embolic episode. The extensive degree of the lesion at
directed at palliation of clinical signs that may be present the time of presentation suggests that most cats with
from arrhythmias or congestive heart failure. If heart RCM present late in the course of disease. Treatment of
failure is present, diuretics including furosemide and an congestive heart failure and/or aortic thromboembolism
ACE inhibitor should be considered (see Chapter 19). prophylaxis is successful in many cats but response rate
If myocardial dysfunction is observed, pimobendan and time to recurrence are highly variable, and they
may be considered at a dose of 1.25–1.5 mg/cat PO q 12 likely depend on owner commitment. The median sur-
hours, although its use in cats is not yet approved in vival of 16 cats with RCM was 132 days in one study
the United States (Sturgess and Ferasin 2007, MacGregor (Ferasin et al. 2003).
et al. 2010).
Because cats with RCM are at a high risk of throm-
boembolic disease, consideration of anticoagulents for REFERENCES
possible prevention of embolic disease is warranted, Boldface font indicates key references.
particularly for cats with significant left atrial enlarge- Bonagura JD, Fox PR. Restrictive cardiomyopathy. In Bonagura JD,
ment (usually a left atrium to aorta ratio of 1.9 or ed: Current Veterinary Therapy XII, Philadelphia, WB Saunders,
greater) (see Chapter 20). 1995, pp. 863–867.
If a supraventricular arrhythmia resulting in an ele- Côté E, Harpster NK, Laste NJ, et al. Atrial fibrillation in cats: 50 cases
(1979–2002). J Am Vet Med Assoc 2004;225:256–260.
vated heart rate is present, medical therapy to control Ferasin L, Sturgess CP, Cannon MJ, et al. Feline idiopathic cardiomy-
the heart rate may be indicated, including digoxin or opathy: A retrospective study of 106 cats (1994–2001). J Fel Med
diltiazem (see Chapter 18). Cats that are being treated Surg 2003;5:151–159.