Hypertrophic Cardiomyopathy in Cats and Dogs

What is a cardiomyopathy?

Cardio refers to the heart, and myopathy means disease of the muscle. Most cardiomyopathies are due to genetic mutations, hereditary conditions, or are of unknown origin. They are not usually caused by systemic diseases or other primary heart disease. Dogs and cats can have several types of cardiomyopathies, including hypertrophic cardiomyopathy (HCM).

What is hypertrophic cardiomyopathy?

Hypertrophic is defined as an increase in the growth of muscle cells. In HCM, the walls of the left ventricle of the heart become excessively thickened over time. Although this heart disease is most common in cats, it can also sometimes occur in small dogs (and in people and cows).

If HCM is severe, muscle cells can actually start to die and then scar, replacing what was once healthy heart muscle tissue with fibrosis. Thickened heart walls combined with a stiff, fibrous heart muscle can lead to a build-up of pressure within the heart and lead to left-sided heart failure and/or a blood clot causing a stroke.

How is hypertrophic cardiomyopathy diagnosed in pets?

HCM is a disease that may not be able to be diagnosed without chest x-rays, an electrocardiogram (ECG or EKG) and/or an echocardiogram (ultrasound of the heart), due to the fact that 1/3 of cats have no obvious heart murmur on auscultation with a stethoscope. However, if it is a chronic or severe disease, your vet may hear a murmur easily, due to changes that occur to the heart valves over time.

A heart murmur can indicate many different types of heart disease, so x-rays and ultrasound are often recommended to further differentiate and to determine if any medications are necessary to help the heart function better. There is also a blood test to examine the levels of a specific heart muscle protein in the blood plasma, which, when elevated, indicates that the heart is working harder than normal.

What are the treatment options for hypertrophic cardiomyopathy?

Treatment is determined on a case by case basis, often by a cardiologist after evaluating an ultrasound of the heart. Medications to thin the blood and prevent blood clots are often prescribed to prevent strokes. Animals that may already be in heart failure may be prescribed medications to increase contractility of the heart, decrease fluid in the body (diuretics), and block calcium channels.

Stable pets with active heart disease on medications are typically advised to be seen by their vet every 3-4 months to recheck bloodwork and make sure the liver and kidneys are tolerating the heart medications.

The survival time is extremely variable for pets with hypertrophic cardiomyopathy. The prognosis for HCM can be very good, as some cats live long full lives with no clinical signs. But once the heart goes into failure, prognosis is very poor and usually their time on this earth is limited. Every once in a while a pet may live for a year or even two years after going into heart failure, but these are very well managed cases, diligent owners, and lucky pets who, for some reason, just didn’t get the memo that they were only supposed to live another 3-4 months. If you have concerns about your pet’s heart condition or medications, it’s important to speak to your vet or veterinary cardiologist right away.

Read more:

Your Pet’s Heart: A Guide to Understanding Heart Health in Dogs and Cats

Can cats develop heart disease?

Congestive Heart Failure in Dogs

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