Feline Hypertrophic Cardiomyopathy ~ Pawprints and Purrs, Inc.

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Any health care links located here are NOT to replace a veterinarian visit; please take your cat to a vet immediately at any sign of odd behavior or any symptoms of illness or injury. Call your vet and describe your cat's symptoms with any of your concerns about the cat's well-being. Your veterinarian may discover changes in your cat's health that you have overlooked. It is always better to err on the side of caution.

This page is dedicated to Hannah, a brave little cat who fought this disease only to be lost to cancer (she's the second AngelKitty on this page) and to her loyal and loving mom, Julie.

Feline Hypertrophic Cardiomyopathy

Heart problems are not as common in felines as they are in humans, but cats are by no means immune to the heartbreak of heart disease. It's not currently known how many cats are affected, because no one has ever looked at incidence across the general cat population. Incidence can vary in different parts of the country, probably because of the gene pool present in a particular area. The most common problem among cats is heart muscle disease (cardiomyopathy) and it causes no end of trouble. Once your veterinarian has diagnosed cardiomyopathy, he will treat it accordingly. In most cases, cardiomyopathy is irreversible, but guardians may be able to add years to their cat's life by diligently sticking to drug treatments and keeping excitement, adventure, and stress to a minimum. Guardians won't necessarily prevent the progression of heart disease, but anything that keeps the heart from racing may help to prevent heart failure.

Research indicates hypertrophic cardiomyopathy may have a genetic component and can affect cats at any age. However, hypertrophic cardiomyopathy is most common in young cats more than one year old and in middle-aged cats. It bears repeating, though, this disease can strike any cat at any age.

In hypertrophic cardiomyopathy, the muscle wall of the heart thickens and stiffens, so the heart's chambers are greatly reduced in volume and can't relax properly after contracting - the chambers can no longer fill with blood.

The severity of symptoms varies from cats who appear totally unaffected to those who die suddenly. A mildly affected cat could very possibly lead a totally normal life. These cats may be identified only when symptoms suddenly develop due to a stressful event, such as bathing or teeth cleaning. Stress causes an increase in the cat's heart rate, which means there's less time for the heart to fill.

Symptoms can be extremely variable:

lack of appetite

gagging

difficulty breathing

increased respiratory rate

reluctance to move around

Affected cats may exhibit labored breathing from pulmonary edema (fluid-filled lungs) or pleural effusion (fluid in the chest cavity around the lungs), which may be present due to congestive heart failure. Poor cardiac output may result in lethargy, weakness or mental depression. Heart failure that results in poor circulation to the intestines and liver may cause reduced appetite or anorexia.

Another dramatic symptom is hind limb pain or paralysis, which results from thromboembolic disease secondary to the cardiomyopathy. Thrombosis is the formation of a blood clot within a cardiac chamber or a vessel and is often seen along with cardiomyopathy. Embolization occurs when the clot breaks off and "gets stuck" in another location, blocking normal blood flow. This type of clot shoots through the circulation and lodges in the distal aorta, back in the rear limbs where the aorta splits. The result is a "saddle thrombus" which causes pain and sometimes paralysis in one or both rear legs.

By the time cats start showing obvious clinical signs of cardiomyopathy, they generally have severe disease. At this point, treatment may not prolong the cat's life, but it may improve the quality of the time the cat has left.

Diagnosis of hypertrophic cardiomyopathy can include:

X-rays - will reveal the presence of fluid in the lungs and chest cavity, and the silhouette of the heart itself. But the cardiac x-ray often looks normal and won't show the thickness of the heart muscle.

Electrocardiography - records the electrical activity of the heart during and between contractions and may pick up abnormalities, such as muffled breathing sounds, extra heart sounds, or gallop rhythms due to the heart chamber enlargement.

Cardiac Ultrasound (echocardiography) - shows thickness in the wall of the heart and how well blood is being pumped. This is usually the determining test of whether a cat has cardiomyopathy and will allow vets to categorize the disease.

Cardiac Catheterization - this will make a specific diagnosis. But because anesthetic risk is high in cats with heart problems, and a definitive diagnosis doesn't change treatment in most cases, this procedure is rarely done.

Treatment depends on the type and severity of the disease and on what owners are willing to do. If the cat is totally without symptoms, therapy may not be necessary. But once clinical signs of heart failure are apparent, intervention with drugs is necessary.

For cats with hypertophic cardiomyopathy, drugs such as diltiazem (trade name Cardizem), propranolol (trade name Inderal), and atenolol (trade name Tenormin) can help reduce heart rate and relax the thickened heart muscle. This disease may lead to congestive heart failure, for which veterinarians often prescribe low-salt diets and diuretics such as furosemide (Lasix®) to reduce fluid accumulation. Lasix® forces the kidneys to get rid of excess sodium and water. Vasodilators such as enalapril may be used as well to reduce blood pressure. If a cat is at risk for blood clots, vets sometimes prescribe small doses of "blood thinners" such as aspirin. But guardians should never give aspirin without consulting a veterinarian. While this medication is harmless to most humans, it can be toxic to cats.

Studies have looked at clot-dissolving drugs like the "clot buster" tissue plasminogen activator (TPA) to treat cats with thromboembolic disease. However, TPA is not only extremely expensive, but severe side effects may occur. One study cites where 50 percent of cats who received the drug ultimately died when the clot dissolved and toxins that had built up on the other side of the clot were released. Other cats suffered spontaneous hemorrhage.

Prognosis of cats with hypertophic cardiomyopathy is affected by both the heart rate and the severity of the symptoms. In the August 1992 issue of the Journal of the American Veterinary Association a study was performed on 74 cases; the median survival for 61 cats was a little over two years. The Journal cited:

Fifty percent of cats with clinical signs and with hypertrophic cardiomyopathy can be expected to die within three months of diagnosis...whereas most cats without clinical signs can be expected to survive more than five years.

Anytime your cat shows a change in behavior, particularly labored breathing or exercise intolerance, consult your veterinarian immediately. Cardiomyopathy isn't preventable or curable, but if caught early, therapy can perhaps improve the cat's quality of life.

Feline Hypertrophic Cardiomyopathy Links for Additional Information:

Case Studies In Small Animal Cardiovascular Medicine
Feline Hypertrophic Cardiomyopathy
Winn Feline Foundation Report

Page URL: http://www.sniksnak.com/cathealth/hyp-cardio.html

Resource References:
Cat Fancy Magazine, January 1995 - Article "Matters of the Heart"
Catnip Newsletter, October 1997, Tufts University School of Veterinary Medicine