Hypertrophic Cardiomyopathy in Cats

Hypertrophic cardiomyopathy in cats is a serious cardiac condition caused by an abnormal thickening of the heart's left ventricle. Today our Boulder emergency vets explain more about HC in cats and how it is treated.

Your Cat's Heart

Like humans, your cat's heart has four sections or chambers, each with a unique and vital role to play. The bottom-left section of the heart is called the left ventricle and it is responsible for receiving oxygenated blood from the lungs and pumping it out to all parts of your cat's body that need oxygenated blood.

While the left ventricle is naturally thicker than the other 3 sections of the heart due to its enormous workload, hypertrophic cardiomyopathy is a condition that occurs when there is an abnormal thicking of the left ventricle. This then negatively impacts the heart's ability to pump the blood out into the body.

Which cats are more prone to hypertrophic cardiomyopathy?

Maine Coon cats have been shown to be predisposed to developing hypertrophic cardiomyopathy due to a gene mutation in one specific (huge!) family line. American Shorthairs and Persians could also face an increased risk of the disease, but the link requires more study.

Male cats are more likely than females to suffer from hypertrophic cardiomyopathy, and the condition is most often diagnosed in cats between 5 - 7 years of age although cats of almost any age can have the disease.

What causes hypertrophic cardiomyopathy in cats?

The causes of hypertrophic cardiomyopathy are largely unknown but genetic mutations and some cat breeds' predispositions towards the disease have been linked to the occurrence of the condition in felines. And while it has not been shown to be a direct cause of the condition, high blood pressure and/or hyperthyroidism can lead to further complications in cats with hypertrophic cardiomyopathy.

What are the signs of hypertrophic cardiomyopathy in cats?

If your cat is suffering from hypertrophic cardiomyopathy the following symptoms may become apparent:

  • Loss of appetite (anorexia)
  • Lethargy
  • Weak pulse
  • Difficulty breathing
  • Shortness of breath, snapping or crackling sounds when breathing
  • Abnormal heart sounds (muffled, galloping rhythm, murmurs)
  • Inability to tolerate exercise or exertion
  • Sudden hind-limb paralysis due to a clot in the terminal aorta (limbs may also feel cold to the touch)
  • Bluish discoloration of the pads of fee and nailbeds (due to lack of oxygen flow to the legs)
  • Collapse
  • Sudden heart failure

How Do Vets Diagnose Hypertrophic Cardiomyopathy in Cats?

EKG testing can be used to analyze the electrical currents in the heart muscles and could reveal potential abnormalities in the heart's electrical conduction. This diagnostic testing can also help your vet to determine the origin of any abnormal heart rhythms detected.

That said, an EKG may not be sufficient for a definitive diagnosis of hypertrophic cardiomyopathy. X-rays and ECG (echocardiograph) performed with ultrasound imaging technology is typically more useful for visually examining the heart for enlargement, thickening of the walls, or other tell-tale signs of the condition.

Your cat's blood pressure will be checked to rule out hypertension, and blood testing will be performed to test for high levels of thyroid hormones. High levels of thyroid hormones are linked to hyperthyroidism in cats which can lead to many of the same symptoms as hypertrophic cardiomyopathy.

Treatment for Hypertrophic Cardiomyopathy in Cats

Cats with hypertrophic cardiomyopathy are typically hospitalized in order to most effectively treat the condition. While hospitalized your cat may receive oxygen therapy to help with breathing and will be kept warm, relaxed and comfortable. Treatment may also include one or more of the following treatments:

  • Diltiazim to slow the heart rate, treat irregular heartbeats, and help in the reduction of the enlargement in the left ventricle
  • Beta-blockers to slow the heart rate, help correct irregular heartbeats, and control blockage of the blood flow.
  • Ace inhibitors, in cases with congestive heart failure to help improve the flow through the ventricle
  • Aspirin to help decrease your cat's risk of blood clots
  • Warfarin to prevent blood clotting
  • Furosemide as a diuretic to help remove excess fluid from your cat's body
  • Spironolactone - a diuretic used sometimes in conjunction with furosemide - for cats with congestive heart failure
  • Nitroglycerin ointment, to improve flow by dilating (opening) the ventricle and arteries

Note that the treatment used for your cat with hypertrophic cardiomyopathy will depend upon your kitty's unique symptoms, overall condition, and any other conditions that may also be impacting your cat's health.

What is the prognosis for cats with hypertrophic cardiomyopathy?

Home care may include a prescription low-sodium diet and a quiet home environment. You will need to observe your cat for any signs of breathing difficulties, weakness, lethargy, loss of appetite, limb weakness, or paralysis.

Ongoing vet care and monitoring will also be required to ensure that treatment is effective and to monitor your cat for any possible side effects such as poor kidney function or bruising.

The prognosis for cats with hypertrophic cardiomyopathy is based on the severity of your cat's condition and other factors that affect your cat's overall health. Your vet will be able to provide you with a realistic prognosis for your kitty.

Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.

Is your cat showing signs of hypertrophic cardiomyopathy? Contact our Boulder vets right away for urgent care.