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February 14, 2019 – Valentine’s Day is a celebration of love and the heart (in a poetic sense) and happens to fall during National Heart Month (very intentional) when healthy heart campaigns for people are in full swing. But did you know heart disease affects our pets as well, including cats?

Morris Animal Foundation has made great strides in learning more about heart problems in cats, and in improving diagnostics, genetic testing and treatments, but more work remains. One serious heart disease posing a threat to cat health is hypertrophic cardiomyopathy (HCM).  

The heart is a specialized muscle, designed to fill with blood then contract, ejecting blood to begin its journey to all parts of the body. Diseases that affect the heart muscle are collectively known as cardiomyopathies. Hypertrophic cardiomyopathy is a type of heart muscle disease characterized by thickening of the heart muscle.

Hypertrophic cardiomyopathy is the most common heart disease diagnosed in our feline friends. A recent study suggests the disease affects one in seven cats, and hypertrophic cardiomyopathy accounts for more than half of all cases of cardiomyopathy diagnosed in cats.

Hypertrophic cardiomyopathy is a heritable condition with some breeds showing an increased prevalence of the disease. Breeds identified at risk include Maine coon cats, ragdoll cats, sphynx, British shorthair, Chartreux, Persian, domestic shorthair and Norwegian forest cats. Male cats also are more likely to suffer from this condition than females.

Because HCM is a heritable condition, many researchers currently are working on diagnostic tests to identify genes that would help veterinarians and owners identify cats prone to developing the disease. These tests also could provide guidance for cat breeders. Some commercial tests are available, and your veterinarian can help you decide whether genetic testing is indicated for your cat.

Diagnosing hypertrophic cardiomyopathy in cats is not easy. Cats are masters at masking when they’re ill – a leftover from their days in the wild when a sick animal was vulnerable to attack. However, there are signs your cat might have hypertrophic cardiomyopathy. These include:

  • Difficulty breathing or increased respiratory rate
  • Sudden hind limb paralysis due to a blood clot to the rear legs (called arterial thromboembolism, ATE)
  • Anorexia and lethargy
  • Weight loss

Unfortunately, many cats exhibit no signs until they’re either in heart failure or develop arterial thromboembolism. Worse yet, hypertrophic cardiomyopathy can cause sudden death.

In a cat without clinical signs, there are physical exam findings that can point to possible HCM. These include a heart murmur, particularly in cases where one has never been detected before, or a gallop rhythm, which is a type of irregular heart beat detected when a veterinarian listens to the heart. In some patients, ruling out other diseases can help cone down the diagnosis.  

The gold standard for diagnosis of HCM remains echocardiogram. Routine X-rays sometimes are helpful for ruling out other problems. Unfortunately, no blood tests can tell whether a cat has HCM.

Once a diagnosis is made, treatment options are tailored to the patient based on echocardiogram results and presence (or absence) of clinical signs. Medications used to treat hypertrophic cardiomyopathy in cats include:

  • Medications to prevent abnormal blood clots from forming
  • Diuretics for patients in heart failure
  • Anti-hypertensive medication
  • Medications such as pimobendan, a drug used to treat heart muscle disorders
  • Antiarrhythmics to control irregular heartbeats

As with so many diseases, early detection is critical to helping cats with HCM live longer. Once a cat has heart failure, or suffers from ATE, the prognosis for long-term survival is poor.

Morris Animal Foundation has been funding studies focused on hypertrophic cardiomyopathy in cats since 1986. Our studies have covered a wide range from early diagnosis of HCM to treating ATE, the deadliest consequence of HCM. But we still have much to learn, and we’re passionate about helping cats with HCM live longer, healthier lives. Learn more about our current and past studies and find out how you can help!