Hypertrophic cardiomyopathy or HCM is a serious, life-threatening heart condition. Cats are good at hiding ill-health so you may not notice any signs of HCM until the condition is advanced. If you have any concerns about your cat’s health, always ask your vet for advice.

To help you understand about hypertrophic cardiomyopathy in cats, we've joined up with Vetstream, experts in the veterinary field, and have put together some information on HCM in cats.

What is Hypertrophic Cardiomyopathy in Cats?

Cardiomyopathy means disease of the heart muscle (cardio = heart and myopathy = muscle disease). Hypertrophic means an increase in size; in this case, the heart muscle becomes thick, stopping the heart from working properly.

The amount of blood flowing through the heart is reduced and in severe cases, this can lead to congestive heart failure and blood clots. These are both serious conditions so it’s good to keep an eye out for any signs. Signs of congestive heart failure can include weight loss, difficulty breathing and anorexia.

Signs of blood clots vary depending on where the clot is, but can include poor circulation, problems with the back legs like cold legs and feet, or even blindness.

HCM can affect cats that are young to middle-aged (5 to 6 years old) or even earlier. The condition is inherited in certain breeds like the British Shorthair, Maine Coon and Ragdoll amongst others.

What Causes Hypertrophic Cardiomyopathy for Cats?

There are two forms of HCM in cats– primary or idiopathic, and secondary. The cause of primary HCM is unknown, although it is likely to be genetic, meaning that some breeds of cats are more likely to develop the condition. Secondary HCM can be caused by conditions that force the heart muscle to work harder than normal, like high blood pressure, thyroid or kidney disease.

What Cat Breeds Often Suffer from HCM?

HCM is seen more often in certain breeds including:

• British Shorthairs
• American Shorthairs
• Maine Coons
• Ragdolls
• Persians
• Sphynxes

Genetic tests are available for Maine Coon and Ragdoll breeds to test whether the cat carries the gene for this condition. There’s also an HCM Negative Register screening scheme under the International Cat Care and Veterinary Cardiovascular Society (VCS). This lists cats that have been tested and identified to be free from hypertrophic cardiomyopathy and are safe to breed from.

If your cat has the gene for HCM or has been diagnosed with it, it’s important that they’re neutered and aren’t used for breeding. This prevents the condition from being passed on.

What Are Hypertrophic Cardiomyopathy in Cats Symptoms?

The clinical signs of this disease in cats can come on really quickly in a cat that had appeared previously well. Affected cats may seem lazy, breathe heavily and may go on to faint or even collapse and die. They may develop a blood clot (called a thromboembolism) which can get lodged in a blood vessel and block the cat’s circulation.

The cat may develop problems with their back legs if the clot lodges in the blood vessels supplying the back legs (this is called a saddle thrombus). If the clot lodges in the blood vessels in the eye, they may become blind.

If you notice that your cat’s hindlimbs appear cold and their footpads become pale or blue/black, your cat needs to be treated as an emergency. FATE is an acronym for Feline Aortic ThromboEmbolism and is another name for a saddle thrombus.

HCM in cats can be diagnosed by ultrasound, x-rays and ECG. Your vet may listen to your cat’s heart to see if they have a heart murmur. An x-ray can show if the heart is enlarged and an ECG will show if your cat has an irregular heartbeat.

The best way of diagnosing HCM is by using ultrasound. This measures the thickness of the heart muscle. If the heart muscle is thickened, it needs lots of energy and oxygen to function. If it’s starved of oxygen, some of the cells start to die and form scars.

This can cause irritation and stops the heart from beating properly. Blood tests will also be taken to monitor for cardiac biomarkers to see if your cat has any underlying health conditions such as thyroid or kidney disease.

What Treatment for Hypertrophic Cardiomyopathy in Cats Is There?

If heart disease is recognised early enough, long-term medication and other steps can slow the disease down. This can include controlling exercise, and special drugs to reduce fluid building up in the lungs such as diuretics and ACE-inhibitors. These drugs allow your cat to breathe more easily. If your cat has HCM their heart rate will usually be high so drugs such as beta blockers may be recommended to reduce their heart rate.

What’s the Life Expectancy of a Cat Suffering from HCM?

This is difficult to predict! It can vary between a few weeks to several years, depending on how far the disease has progressed and if blood clots have developed. Cats that are asymptomatic, i.e. don’t have any signs or symptoms, may live to a good old age without the need for any medication.

But, if your cat is very poorly and has suffered a thromboembolism, the prognosis may not be so good and sadly, sudden death can occur. On a brighter note, most cats can remain stable on long-term medication and lead a good quality of life.

Spotting any problems early on is so important, so always check with your vet if you are concerned about your cat.

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Content provided from Vetstream's Vetlexicon Felis - www.vetlexicon.com/treat/felis

Vetlexicon is the world’s largest peer-reviewed online clinical reference source. All our content is written and peer-reviewed by over 1,000 of the world’s leading veterinarians, ensuring relevance, accuracy and quality.