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CARDIOMYOPATHY
What is cardiomyopathy?
Cardiomyopathy is a term used to describe diseases of the heart muscle. In cats, at least three classes
of cardiomyopathy have been described. In all cases, the heart disease may result in clinical signs of
heart failure. Cardiomyopathy may be seen as a primary condition or secondary to other diseases.
What are the clinical signs seen with cardiomyopathy?
In the early stages of disease, the cat may be able to cope and hence show no signs of disease. This
situation is referred to as compensated heart disease. Often the cats will alter their activity levels to
those that they can cope with which makes it difficult to diagnose cardiomyopathy until it is quite
advanced.
The major longterm concerns with all types of cardiomyopathy are:1.
Development of congestive heart failure: Breathlessness and lethargy are the most
frequently noticed signs of congestive heart failure and these result from a failure of the heart
to efficiently pump blood. Blood banks back into the blood vessels of the lungs, resulting in
fluid accumulation in or around them.
2.
Thromboembolic disease: Altered flow of blood in enlarged heart chambers predisposes to
the formation of a blood clot within the chambers of the heart. This becomes organised and is
known as a thrombus. If parts of the thrombus become dislodged they can travel in the
bloodstream and become lodged in smaller blood vessels. These particles are called emboli
and the most common place for them to lodge is at the bottom of the aorta which is the biggest
artery in the body. This results in obstruction of the blood supply to the back legs which is
usually very painful and the back legs become paralysed and cold to the touch. Although a
minority of cats may recover completely with appropriate treatment, this is a potentially fatal
complication of any cardiomyopathy. In some cats, a partial recovery which may take a long
time, is seen.
How is cardiomyopathy diagnosed?
Diagnosis of heart disease can be suspected on the basis of clinical signs, such as those of
congestive heart failure, in addition to more specific tests such as chest x-rays. Electrocardiography
(ECG) rarely provides useful information on heart conduction and size. Cardiac ultrasound scans,
where available, are indispensable in distinguishing between the different types of cardiomyopathy.
Specific tests may be done in order to check that the cardiomyopathy is not secondary to some other
disease. (see below).
What causes cardiomyopathy?
There are many causes of cardiomyopathy, however, in older cats thyroid disease (hyperthyroidism)
may cause a type of cardiomyopathy. Other causes include dietary deficiency of taurine, an essential
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nutrient. This is not seen in cats fed a commercial cat food or fresh meat. Often, no cause of the
cardiomyopathy is found.
How is cardiomyopathy treated?
In cases where an underlying cause of the heart disease is found, then treatment of this may result in
improvement or reversal of the heart disease. Hyperthyroidism is the most treatable cause of
cardiomyopathy since complete resolution of the heart disease is possible if treated early. In cases
where no cause is identified, (referred to as idiopathic cardiomyopathy), and in cases where disease
remains following treatment for an underlying cause then medication may be needed.
Treatment varies according to each case but may include:1.
Diuretics if congestive heart failure is present.
2.
Beta blockers to reduce the heart rate where this is excessive.
3.
Calcium channel blockers to help the heart muscle relax and hence help more effective filling
of the heart. These drugs are generally the most effective form of treatment and often are the
only drug required (in the long term).
4.
Aspirin may be used for its effects at reducing the risk of thrombus formation and hence
thrombo-embolic disease although it is being used less frequently these days for this purpose.
Dosing of asprin should always be as advised by a veterinary surgeon since aspirin may be
toxic to cats. Aspirin poisoning, which occurs if the dose or frequency of aspirin
administration is too high, may cause vomiting and internal bleeding. If your cat shows these
signs, goes off their food or is sick then aspirin therapy should be stopped and you should
consult your vet.
5.
ACE inhibitors - these drugs also help to control congestive heart failure.
The longterm outlook for a cat with cardiomyopathy is extremely variable depending on the
cause of this disease. Cats with idiopathic cardiomyopathy may remain stable for several years
and lead near-normal lives.
Does a cat with cardiomyopathy need a special diet?
Other than in cases of taurine deficiency, no specific diet is recommended although excessively
salty foods, e.g. dry cat food should be avoided since these will predispose to fluid retention. This
may increase the risk of congestive heart failure. Proprietary cat foods are usually adequate although
special low salt diets are available and may be recommended by your veterinary surgeon in specific
cases. Cat treats are often quite salty and probably should be avoided.
Ark Veterinary Centre
A Lifelearn Product from:.
Arthur Webster & Associates Pty Ltd
P O Box 438, PYMBLE NSW 2073 Australia