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HCM Testing in Cats
Updated on January 11, 2023
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Cat Testing
HCM Testing in Cats

Humans and animals suffer from similar diseases.

This includes:

  • obesity
  • heart problems
  • cancer
  • diabetes
  • kidney diseases

There’s been an earlier debate among veterinarians on whether cats develop cardiovascular diseases, too. Like many animals, they do. This occurs when the heart doesn’t perform at the optimal level or when it doesn’t perform at all. Most of the cardiovascular cases in cats are rare, but they exist.

One of the most common heart disease in cats is hypertrophic cardiomyopathy (HCM). It affects about 10-15% of cats.

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What is Hypertrophic Cardiomyopathy (HCM)

Hypertrophic cardiomyopathy in cats is a genetic condition. It causes an abnormal thickening of the heart muscle (hypertrophy).

With HCM, the heart's left ventricular wall becomes thick. This causes an abnormal decrease in blood volume pumped by the heart.

HCM is a progressive condition. If not well managed, most affected cats develop heart failure. This might occur when the heart muscle is scarred enough to affect overall heart function.

What causes HCM in cats?

There’s no known cause of hypertrophic cardiomyopathy in cats. However, there are many theories on what could be the possible cause of the condition.

The three main factors that may predispose your cat to HCM are:

  • Genetics
  • Hypertension and Hyperthyroidism
  • Nutrition

There is no concrete evidence that shows that the above conditions cause HCM. But, research suggests a possibility of them being the cause.


Genetic predispositions have been noticed in some cat breeds. Research has identified two mutations in genes associated with HCM. Cat breeds such as Maine Coon cats and Ragdoll cats were identified to possess this mutated gene.

This research goes on to identify that HCM is an autosomal dominant inherited trait. It happens because of gene mutations.

The mutated gene responsible for HCM is expressed differently. This means it can be severe in some cats, may be mild in some.

Some cats may not have any signs but will produce affected kittens. However, from all the genetic studies done on this condition, no genetic cause has been identified.

Veterinarian geneticists are working hard to identify the gene that causes this condition. However, the study of the genetic cause of HCM seems bothersome. This is because not many veterinarians specialize in genetics and cardiology.

Also, the problem of variation of genes may pose a problem. For example, the gene responsible for HCM in Ragdoll cats may differ from the gene expressed in the Maine Coon cat. The studies would demand a study of each cat breed individually.

Hypertension and Hyperthyroidism

Other diseases such as hyperthyroidism and high blood pressure are also known causes. Although they are not the primary causes, some studies show that HCM developed in most hyperthyroid cats.

Hyperthyroidism causes the thickening of the heart’s left ventricle, leading to congestive heart failure (CHF). If your cat suffers from hyperthyroidism, your vet should check for HCM.



Nutrition may also cause HCM, but there’s no known evidence to suggest that. However, nutrient-gene interactions can provide an opportunity to study the condition’s severity.

Obesity is one of the risk factors of HCM. Studying nutrition and how food is processed in the cat’s body can provide a clue on how it affects the heart.

Most cats with HCM are usually overweight and have higher glucose concentrations. They develop more quickly in size when compared to healthy cats. Studying cats' growth, development, and nutrition may be key to determining the influence of nutrition in HCM.

What are the Signs of Hypertrophic Cardiomyopathy in Cats?

The signs seen in cats with HCM are usually noticeable. Some affected cats show no signs of illness, especially in the early stages of the disease. In more severe cases, the heart muscle becomes so stiff that an apparent heart failure occurs. 

The prominent clinical signs and symptoms of HCM include:

  • Fatigue
  • Difficulty of breathing (dyspnea)
  • Rapid breathing (tachypnea)
  • Low activity
  • Pale mucous membranes
  • Collapse episodes
  • Sudden death

Fatigue is caused by poor blood transportation in the cat’s body. This results in oxygen depletion in body cells. If oxygen is low or absent, cells won’t function well and tend to reserve energy by making your cat weak.

The difficult and rapid breathing is caused by fluid accumulation around the lungs or inside the lungs themselves. This may cause your cat to labor for breath or breathe heavily.

Cats, unlike dogs, don’t usually get much exercise. This makes it incredibly difficult to notice breathing problems. Inability to exercise is usually indicative of HCM onset.

The pale mucous membranes result from poor blood circulation around the body. This causes the membranes around the mouth to appear pale.

The collapse episodes are when you may require aggressive medical attention for the cat. It’s one of the critical signs of potential heart failure, which may lead to sudden death.

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How do Vets Diagnose Hypertrophic Cardiomyopathy? 

Veterinarian cardiologists diagnose hypertrophic cardiomyopathy using an echocardiogram (ECG). 

It is the gold standard for detecting HCM in both cats and humans. It involves the ultrasound scanning of the heart to detect irregular rhythm.

However, before applying any diagnostic methods, your vet is likely to run some minor checks. These include:

Heart Murmur

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Using a stethoscope, your vet will check for a heart murmur. It is an abnormal sound caused by irregular blood flow in the heart. Not all heart murmurs will signify that your cat is suffering from HCM.

Some heart murmurs are innocent or physiologic. Your vet would notice this and will determine if your cat requires further screening.

Gallop Rhythm

Gallop rhythm is an irregular heart sound heard when a part of the heart contracts, allowing blood to flow into the stiff left ventricle.

In HCM, where the left ventricle is already stiff, the vet can hear a third and fourth heartbeat when placing a stethoscope on the cat’s chest area.

Irregular heart rate

Your vet would check the rate of your cat’s heartbeat. Your cat’s heart rate is likely to be too fast or too slow when HCM is involved. Sometimes, the heart can beat for several episodes without pumping any blood.

Your vet would run lots of tests to determine whether these conditions are temporary or a result of an onset of HCM.

Irregular heart rhythms

As electrical impulses control the heart, minor disturbances can cause a change in these impulses. This can lead to irregular heart rhythms, also known as arrhythmias.

Normally, cats have irregular heart rhythms when they are stressed, nervous, or scared. However, it is necessary to take your cat to your vet at least once a year.

Since irregular heart rhythm can also be a sign of HCM, your vet can detect the disease early and take necessary precautions in its management.

Other Diagnostic Tests 

There are other options used to detect hypertrophic cardiomyopathy in cats. Since an echocardiogram is expensive and usually not readily available, your vet may consider these equally effective but cheaper methods.

These methods include:


Radiography is used to monitor and evaluate the cat’s heart shape and size. However, there’s a limitation to this method.

Results from ordinary radiography fail to differentiate between cats with cardiac disease from the ones without cardiac disease. This is because heart conditions like HCM do not involve the enlargement of the heart.

Thoracic Radiography

`Thoracic radiography has become one of the most common diagnostic methods used in detecting heart diseases in cats. This method is mostly used to detect cardiogenic pulmonary edema (accumulation of fluids in lungs, caused by heart diseases).

It has a low sensitivity in detecting the enlargement of the heart. However, It has higher accuracy in detecting other parameters associated with heart diseases. 

Thoracic radiography also has high accuracy in differentiating between cardiac and non-cardiac disease, making it a reliable tool in diagnosing cats for HCM.

Gene testing

Since genetics can give a clue about the presence of HCM in cats, a genetic test can be regarded as one of the diagnostic tools to consider. The gene test evaluates the genetic profile of the cat and determines if any gene mutation has occurred, which may predispose the cat to HCM.

The Maine Coon cats and Ragdoll are the few breeds of cats predisposed to HCM genetically. They should be screened for HCM using the gene test.

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Other methods such as blood tests can also be considered as a diagnostic tool.

How often should you test your cat for HCM? 

Usually, only cats with known indications of hypertrophic cardiomyopathy are tested for the disease. However, you should not rule out regular visits to your vet to be safe.

Echocardiography(ECG) is one of the best methods for diagnosing HCM. Some cats go through ECG, but the vets fail to detect any signs of HCM. Due to irregular veterinary visits, most cat owners only visit the vet when they notice abnormal behavior in their cats.

The best way to make use of this diagnostic tool is to visit your vet at least once a year. Regular visits will help the vet look at other details that may be associated with the disease. 

You can remind your vet to include the HCM test as part of the schedule during your visits.

Does HCM affect cats of all ages? 

Yes. Hypertrophic cardiomyopathy affects cats of all ages. HCM has been detected in newborn kittens and adult cats. In humans, men are more prone to HCM than women. This situation is also the same with cats. 

In Maine Coons, the disease usually starts early at two to three years of age in males and three to four in females. Although it rarely occurs in female cats as compared to the male. 

Ragdolls, in contrast, tend to develop HCM under one year of age. The testing guideline for other cats is not yet available. However, it seems reasonable to start HCM testing in cats around 1 to 2 years of age.

Since HCM affects cats of all ages, you should not relax after one test. You may be required to test your cat yearly to avoid missing any sign of HCM in your cat.

What to do if your cat is diagnosed with HCM?

It’s not the end of the world if your cat gets an HCM diagnosis. Most cats live through the disease, but it requires a dedicated effort from the owner. 

When you get the results, the first thing to do is talk to a veterinary professional about how you will go about it. 

Lifestyle Recommendations and Precautions 

Your vet is likely to provide adequate information you need to manage the disease and give your cat a better life. 

The next thing to do is stick to the information given to you religiously and apply every step given. You can also pay regular visits to the vet if there is any other information or changes you need to make. 

If you’re a breeder, you might need to do the following:

  • Remove all diagnosed cats from any breeding program. Don’t breed any cat from the HCM-diagnosed cats. If this happens accidentally, monitor the kittens and test them for any potential occurrence of HCM.
  • Test and monitor all cats from the Maine Coons and Ragdoll breeds and make sure they are free from HCM before breeding.
  • Some cats can have one normal gene and one abnormal gene. These cats would pass 50% of the genes to their offspring. The best practice is to remove them from the breeding program entirely.

Applying these principles will have your cat live longer and healthier even with HCM. It can also help cat breeders to take extra caution while running a breeding program. 

Most HCM are mild. Some come with just heart murmurs. However, the condition can go from mild to severe if the cat owner doesn’t show enough care to improve the cat’s quality of life. 

Final words

Cats suffer from HCM as much as humans do. HCM stiffens the heart muscle, preventing the heart from pumping enough blood required for the overall well-being of your cat. If this is not well managed, it can lead to heart failure.

HCM occurs mainly in Maine Coon cats and Ragdolls. They are the only breed confirmed to have a genetic predisposition to the disease. Other cat breeds are yet to be studied.

There's no known treatment or cure for HCM for now. However, it is necessary to run several tests on your cat to determine whether it is prone to HCM or not. The best way to know this is to visit the vet regularly. 

Regular visits to the veterinary clinic provide you with information about HCM. It may also uncover other underlying illnesses in your feline friend.

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Updated on January 11, 2023
Dr. Alam
Dr. Alam Roky
Medical Reviewer
Dr. Shamsul Alam Roky is a registered veterinarian who graduated from the Faculty of Veterinary, Animal, and Biomedical Sciences. Currently, he is working as a graduate research assistant at his university, in addition to running a private veterinary clinic named ‘Sylhet Veterinary Services” in his city.
Joel Hirsch
Joel Hirsch
Content Contributor
Joel Hirsch is a health enthusiast and gym rat with a degree in Health Sciences. He spends his time writing about products that help people reach their health goals.
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