What Is Hypertrophic Cardiomyopathy (HCM) in Cats?

Hypertrophic cardiomyopathy (HCM) in cats is a heart condition that may cause heart muscles to thicken. The condition reduces the heart’s efficiency. Symptoms may show in other body parts. Hypertrophic cardiomyopathy is more common in certain cat breeds, including the British shorthair, Maine coon, Chartreux, Ragdoll, Persian, and Sphynx.

What Causes HCM in Cats?

There is no conclusive research on what causes feline hypertrophic cardiomyopathy. The heart condition will mostly affect specific cat breeds and male cats who have reached middle age.

Hypertrophic cardiomyopathy is the most common heart condition in cats. The prevalence of hypertrophic cardiomyopathy in the cat breeds listed above may suggest that the condition has a genetic origin.

What Are the Symptoms of HCM in Cats?

Sometimes your cat may not show any symptoms of hypertrophic cardiomyopathy. As the condition worsens, your cat may get symptoms like:

• Lethargy (extreme exhaustion)
• Difficulty breathing
• Weakness
• Open-mouth breathing (after exercise)
• Abdominal distension (due to fluid accumulating in the chest)
• Collapsing
• Heart failure
• Paralysis of the back legs (due to blood clots)
• Sudden death

How Is HCM in Cats Diagnosed?

Your cat’s veterinarian might choose to use echocardiography to diagnose hypertrophic cardiomyopathy. Echocardiography is a type of ultrasound used to check the thickness of the left ventricle. Your cat’s vet may also have to do some tests to rule out other heart conditions like hyperthyroidism and hypertension, which may have similar symptoms to hypertrophic cardiomyopathy. 

Additional tests used to confirm hypertrophic cardiomyopathy in cats are:

• Physical exam findings
• Electrocardiogram
• Blood sample
• X-ray

What Is the Treatment for HCM in Cats?

Hypertrophic cardiomyopathy treatment may depend on the severity of your cat’s condition. A mild case may not need medical intervention. After your veterinarian has confirmed the presence of hypertrophic cardiomyopathy with the help of an echocardiogram and blood tests, they may recommend medications, including:

• Angiotensin-converting enzyme inhibitors (like enalapril or benazepril)
• A diuretic (furosemide)
• Beta-blockers (atenolol or carvedilol)
• Clopidogrel
• Pimobendan

Your vet may also recommend a low-sodium diet for your cat in addition to the medications.

How Can I Prevent HCM in My Cat? 

There is currently no conclusive research on how to prevent hypertrophic cardiomyopathy from happening. More studies are being done on medications that might help slow or reverse the progression of the condition.

How to Care for a Cat With HCM

Cats with feline hypertrophic cardiomyopathy will generally live well on medications. Simple dietary modifications might be sufficient to manage your cat’s condition in the early stages. Keep an eye on your cat to detect any signs of the condition early. Look for breathing issues, tiredness, weakness, or a loss of appetite. The earlier you diagnose and treat HCM, the easier it might be to prevent a crisis like heart failure and blood clots.

You might also need regular follow-up visits to your veterinarian for repeat blood tests, echocardiography, and medication adjustments. That may help ensure that the heart medications are working without negatively affecting your cat’s kidneys and electrolyte levels.

The outcome of your cat’s heart condition is dependent on whether symptoms are showing or not. A cat who has developed a clot in their back legs might not survive for long. Classic signs of a blood clot are sudden pain and paralysis of the back legs. It might take weeks for a cat to regain their leg function and walk again. Some cats lose their leg function completely. If your cat survives a clot, it might take around two to six months for a repeat episode to happen.

Heart medications are fairly effective in controlling HCM symptoms and preventing blood clot formation. Your cat may live on after a hypertrophic cardiomyopathy diagnosis if you do frequent checkups. Some cats might even live up to three years or longer after the start of heart failure.

You may be forced to euthanize your cat if the HCM progresses and starts affecting their quality of life. Consider talking to your veterinarian about your cat’s condition and what to expect.

Other Common Heart Conditions in Cats

Other common heart conditions that affect cats aside from hypertrophic cardiomyopathy include:

1. Dilated cardiomyopathy (DCM): Dilated cardiomyopathy causes the wall of the heart to become thin, making it weaker. 
2. Congenital heart disorders: Here, your cat may be born with a heart defect like a ventricular septal defect (VSD), mitral valve dysplasia (MVD), and patent ductus arteriosus (PDA).
3. Restrictive cardiomyopathy (RCM): Restrictive cardiomyopathy causes the heart not to fill with blood as it should.
4. Arterial thromboembolism (ATE): Arterial thromboembolism involves a blood clot forming in the cat’s blood vessels and blocking the blood flow.