Hypertrophic Cardiomyopathy in Cats

Causes, Treatment, and Prevention

Doctor veterinarian at clinic.
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Hypertrophic cardiomyopathy (HCM) affects a cat's left ventricle, inhibiting blood flow and potentially causing health issues throughout its body. Cats don't always show symptoms of HCM, but when they do, symptoms may include labored breathingcollapse, and an irregular heartbeat. HCM is caused by a mutated gene and disproportionately affects Maine coonsrag dollsPersianssphynxsChartreuxs, and British shorthairs. A vet will diagnose HCM with a comprehensive physical examination and diagnostic tests like an electrocardiogram. Because the cause of the mutated gene isn't understood, HCM can't be prevented. The prognosis is good for asymptomatic cats but varies for cats showing signs of heart failure. 

What Is Hypertrophic Cardiomyopathy?

Hypertrophic cardiomyopathy (HCM) is a condition that causes the muscular walls of the heart to thicken, especially the left ventricle—the primary pumping chamber of the heart. As a result, the left ventricle shrinks, enlarging the left aorta, and potentially leading to heart disease. When the left ventricle thickens, the heart can't adequately pump blood, creating other problems in the body, including blood clots and congestive heart failure. HCM causes the heart rate to increase to compensate for the lack of proper blood flow, and, in doing so, depletes the body of oxygen, killing heart cells. When the cells die, the heart function decreases even more. HCM is the most common heart condition in cats.

Symptoms of Hypertrophic Cardiomyopathy in Cats

Not all cats present HCM symptoms, but they may come on suddenly and acutely if they do. If your cat seems ill, visit your vet right away.


  • Labored breathing
  • Pale or blue gums
  • Collapse
  • Weakness
  • Irregular heartbeat
  • Hind limb paralysis

The symptoms of HCM in a cat will typically resemble those of congestive heart failure. Labored breathing is usually identifiable by observing your cat taking quick breaths and wheezing audibly. You may notice its abdomen rising and falling instead of the chest, an open mouth, heavy panting, and pale or blue gums. The lack of oxygen can lead to weakness and collapse. HCM can also cause sudden hind limb paralysis if a clot travels out of the heart and blocks blood flow to the legs. This onsets suddenly and is sometimes accompanied by the limb feeling cold to the touch.

Causes of Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy is an inherited disease caused by a mutated gene. Certain breeds are more likely to develop hypertrophic cardiomyopathy than others. Maine coons, ragdolls, Persians, sphynxs, Chartreuxs, and British shorthairs have a genetic predisposition to HCM. The reason for the genetic mutation is unknown.

Diagnosing Hypertrophic Cardiomyopathy in Cats

To diagnose your cat with HCM, your vet will begin with a full physical examination and search for an abnormal heart rhythm. If your vet finds a heartbeat irregularity, they will likely perform an echocardiogram which will create an image of your cat's heart and show the thickened wall if present. Your vet will rule out other illnesses may cause thickening of the left ventricle, with additional diagnostic tests before making an HCM diagnosis. Your vet will likely run blood analysis and urinalysis in addition to imaging tests.

Treatment & Prevention

Treatment for HCM depends on the severity and stage of the condition. Overall, treatment is aimed at improving heart function, limiting the symptoms of heart disease, and minimizing the chance of blood clots developing. While you can take measures to manage HCM, there is no cure. Your vet may administer oral or injection medications if your cat is healthy enough to tolerate them. If your cat suffers from breathing problems due to HCM, your vet may suggest oxygen therapy. In addition to medication, your cat may be placed on a low-sodium or high fatty acid diet, and your vet may recommend keeping your cat's activity level and stress level low to minimize strain on the heart.

Because HCM is an inherited disease, it isn't preventable, but providing proper nutrition to support the heart and keeping up with annual veterinarian examinations is essential to ensuring your cat's heart is healthy.

Prognosis for Cats With Hypertrophic Cardiomyopathy

HCM is a progressive disease and will worsen over time. The prognosis for cats with HCM varies depending on your cat's symptoms. Some cats whose symptoms progress rapidly will die suddenly, while others with slow onset will live unaffected lives. Early detection of HCM is essential to enlongating your cat's life as much as possible.

  • How can I tell if my cat has HCM if it isn't showing symptoms?

    It's difficult to detect HCM in an asymptomatic cat. However, if your cat isn't showing symptoms, its health and quality of life will likely be unaffected.

  • Why does HCM cause hind limb paralysis?

    HCM can cause blood clots that travel to the limbs and block blood flow, causing paralysis. If you notice your cat showing symptoms of paralysis, visit your vet immediately.

  • Is HCM inherited?

    If one of your cat's parents has HCM, there is a chance they have passed along the gene. Discuss possible genetic testing with your vet if you know there is HCM in your cat's family.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.
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  1. Hypertrophic Cardiomyopathy. Cornell University College Of Veterinary Medicine.

  2. Acquired Heart and Blood Vessel Disorders in Cats. Merck Veterinary Manual.