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HCM is the abbreviation for “Hypertrophic Cardiomyopathy”, one of the most common heart diseases in cats. We explain what to look out for if your cat is suspected of having HCM or has been diagnosed with HCM.

What is HCM in cats?

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In HCM, to put it simply, the following happens: The heart muscle becomes thicker and stiffer so that the heart can no longer fill up with sufficient blood. The result: its pumping capacity drops. As a result, the organs are no longer adequately supplied with oxygen in the further course of the process. The chest and lungs fill with water, making it difficult to breathe.

In most cases, HCM is an inherited condition that can affect all breeds of cats. Some cats are carriers, but they never show symptoms or show symptoms very late. Yet they pass the disease on. HCM that is spontaneous or caused by illness – for example, an infection – is less common.

Symptoms of HCM

Cats with HCM do not show symptoms until a late stage. The first sign may be panting after a short exertion. If the weak heart leads to bluish mucous membranes, shortness of breath, or tiredness, the disease is well advanced. By the way: unlike dogs, cats rarely cough due to heart disease. Anyone who knows that close relatives of their own cat have HCM should also have symptom-free velvet paws examined cardiological.

Investigation and diagnosis

An ultrasound examination of the heart is necessary to rule out or confirm an HCM diagnosis.

The cat’s heart ultrasound

HCM can only be diagnosed with certainty using a heart ultrasound. This requires a special ultrasound device with color Doppler, which is only available in a few veterinary practices. HCM usually manifests by the age of seven. If the animal is older and no thickened heart wall can be seen on the ultrasound, it is likely to remain healthy. If you suspect your cat has HCM, it is best to contact a specialist. The examination takes up to half an hour and is painless. HERE you will find a list of cardiological trained veterinarians.

Is there an HCM test for cats?

No. With some cat breeds, there is the possibility to prove the system for HCM by means of a genetic test. Unfortunately, a negative test does not mean that the cat will not develop HCM. Because there are many possible mutations for the disease that the genetic tests do not cover. For comparison: There are 180 different mutations in humans that can lead to HCM. For breeders, this means that only regular ultrasound examinations of the parent animals can offer the greatest possible safety. Unfortunately, many shy away from the resulting costs.

Therapy for HCM in cats

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HCM is not curable. However, regular check-ups and appropriate medication slow down the process in many cases.

Heart medication for cats

Depending on the heart rate and blood pressure, beta-blockers such as atenolol or ACE inhibitors are used to relieve the heart. The majority of cats tolerate these drugs well and without side effects. An experienced veterinary cardiologist can assess when medication is necessary.

Treat water in the lungs

HCM is often not diagnosed until the heart is so weak that water collects in the lungs and chest. The vet will prescribe drainage tablets that your cat will need every day from this point on. In some cases, a puncture of the lungs is required.


In order to be able to observe the course of HCM in cats, regular ultrasound monitoring is useful. This is the only way for the vet to adjust the medication. At the beginning, the intervals between the examinations are shorter in order to observe whether the four-legged patient responds to the medication. If this is the case, an annual check is sufficient for many.

A cat with heart disease: the cost

The costs for a cat suffering from HCM cannot be quantified across the board. The price for the ultrasound examination alone varies between 100 and 200 euros. Practices or clinics with little experience with sound are often more expensive in order to earn the high purchase price for the ultrasound device. Dehydrating medication only costs a few euros per month. The prices of heart drugs, by the way, differ greatly.

Tips for living with an HCM cat

Enjoy the time with your velvet paw! Keep an eye on your breathing rate at rest: If the cat breathes more than 40 times per minute at rest, you should contact the veterinarian. Slow-moving animals often reach a high double-digit age (life expectancy). Protect your cat from stress and obesity and take more breaks when playing.

Terminal HCM

Pulmonary edema

In addition to increased breathing rate, panting can be a symptom of water in the lungs after brief exertion. The vet will recognize this on an X-ray. Thanks to dehydrating medication, some velvet paws can still live for years without restriction. However, when it comes to drainage, the following applies as much as necessary, as little as possible. Because the therapy damages the kidneys in the long term.

Thromboembolism in cats

In advanced HCM, thromboembolism is a dreaded complication. This is a blood clot caused by poor blood flow in the heart. An accomplished animal cardiologist can read the risk of thromboembolism on ultrasound by looking at the size of the left atrium and prescribing preventive medication. But these do not protect 100 percent.

In cats, thromboembolism usually occurs in the hind limbs (aortic thrombus). One or both legs are paralyzed, cool to the touch, and in great pain for the cat. It belongs immediately to the vet or to a veterinary clinic. It is only possible to dissolve the thrombus with medication within a few hours. Unfortunately, this does not always succeed and there is a high relapse rate: around 50 percent of the animals suffer another thromboembolism in the next few weeks. Some owners, together with their vet, decide to euthanize the cat at this point.

Preventing HCM in cats

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Consistent control of the parent animals protects against genetically caused HCM. Not only breeders are responsible: As a cat lover, buy from responsible breeders.

Course and life expectancy in cats with HCM

Every HCM history is different. Basically, the earlier the animal shows symptoms, the more unfavorable the course.

A practical example describes three related animals: a tomcat and two of his sons from one litter. The breeding tomcat was diagnosed with “mild HCM” at the age of five and henceforth beta-blockers and ACE inhibitors. This means that he has reached an old age of 18 years without any symptoms. The two sons inherited the disease. One of them dies at the age of three as a result of pulmonary edema. In the second, HCM is milder: at the age of four, he is diagnosed with HCM and given appropriate medication. From the age of nine, he needs additional drainage. At 15 he suffered thromboembolism and was put to sleep.

If HCM is detected before the first symptoms appear, medication can significantly extend life.