Thickened heart muscle in cats - Hypertrophic cardiomyopathy (HCM)

A thickened heart muscle in cats, also known as hypertrophic cardiomyopathy (HCM), is the most common heart disease in cats. In this condition, the left heart muscle becomes abnormally thick, making it harder for the heart to relax and fill with blood. This ultimately leads to reduced pumping function and, in severe cases, to heart failure or sudden death.

In this article, we discuss the causes, symptoms, diagnosis, and treatment of HCM in cats.

What is hypertrophic cardiomyopathy (HCM)?

HCM is a condition in which the left heart muscle becomes abnormally thickened. As a result, the heart cannot fill properly with blood, leading to increased pressure in the heart and lungs. The disease often progresses insidiously and can be present without symptoms for a long time.

Causes of HCM in cats

• Hereditary predisposition: occurs in both pedigree and non-pedigree cats
• Gene mutations that affect heart muscle function
• Secondary causes such as high blood pressure or hyperthyroidism (thyroid gland disorder)
• Age: usually diagnosed in adult to older cats

Symptoms of HCM in cats

In cats, heart conditions often progress for years without clear symptoms. Symptoms usually only become visible once the condition is already well advanced and the cat is heading into (early) heart failure.

Possible symptoms include:

• Rapid or labored breathing
• Reduced activity or sudden lethargy
• Fainting spells or collapse
• Loss of appetite and weight loss
• Sometimes sudden death without any clear prior symptoms
• Complications: blood clots (aortic thromboembolism) causing paralysis of the hind legs

Diagnosis of HCM

HCM in cats is diagnosed using:

• Physical examination: sometimes a heart murmur or abnormal heart rhythm can be heard
• Echocardiography: the gold standard for assessing the thickened heart muscle
• X-rays: may show an enlarged heart or fluid in the lungs
• ECG: to detect heart rhythm disturbances
• Blood tests: to rule out secondary causes such as hyperthyroidism

Treatment of HCM in cats

HCM cannot be cured, but the symptoms and complications can often be well managed:

• Medication to support heart function, such as beta-blockers or calcium channel blockers
• Diuretics (water tablets) for fluid in the lungs
• Anti-clotting medication/anticoagulants to prevent the formation of blood clots
• Treatment of underlying conditions such as hyperthyroidism or high blood pressure
• Regular monitoring with ultrasounds and check-up appointments

Prognosis

The prognosis for cats with HCM varies greatly. Some cats live for years without symptoms, while others quickly develop serious symptoms. The presence of complications such as blood clots and heart failure significantly worsens the prognosis. Early detection and good follow-up are crucial for the best possible quality of life.

Want to know more?

Read more about cardiology and heart disease in cats at Nesto. Our specialized veterinarians have extensive experience in the diagnosis and treatment of HCM and other heart muscle conditions.

Frequently asked questions (FAQ)

What is the most common heart disease in cats?

Hypertrophic cardiomyopathy (HCM), a condition in which the heart muscle becomes thickened.

Does HCM only occur in pedigree cats?

No, it can also occur in regular domestic cats, but pedigree cats have an increased risk.

How is HCM diagnosed?

With a heart ultrasound (echocardiography), often supplemented with blood tests and an ECG.

Can HCM be cured?

No, the disease cannot be cured, but medication can improve quality of life.

What is a dangerous complication of HCM?

The formation of blood clots (aortic thromboembolism), which can lead to sudden paralysis of the hind legs.