Hypertrophic Cardiomyopathy in Cats

Your Cat's Heart

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

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

Are some cats more prone to developing hypertrophic cardiomyopathy?

Maine coon cats have been shown to be predisposed to developing hypertrophic cardiomyopathy due to a gene mutation in one specific (very large) family line.  American Shorthairs and Persians may also appear to 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 cat's 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 predispositions in some breeds have been linked to the occurrence of hypertrophic cardiomyopathy in cats. 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 with cold limbs due to clot in the terminal aorta
• 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 see hypertrophic cardiomyopathy in cats?

EKG testing can be used to examine the electrical currents in the heart muscles and may reveal possible abnormalities in the heart's electrical conduction. EKG 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.

What is the 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 relaxing home environment. You will need to monitor your cat for any signs of breathing difficulties, weakness, lethargy, loss of appetite, limb weakness or paralysis.

Ongoing veterinary care and testing 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 mixed 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 a diagnosis of your pet's condition, please make an appointment with your vet.