Hypertrophic cardiomyopathy in cats: signs, scans and veterinary care

Feline hypertrophic cardiomyopathy (HCM) is a condition in which part or all of the wall of the heart's main pumping chamber is thickened while the chamber itself is not enlarged.

The main pumping chamber is called the left ventricle. In HCM, thickening may affect the whole wall or only one region of it. [1]

Yes. High blood pressure and an overactive thyroid can also produce a thickened-heart-wall pattern in cats.

Vets therefore check blood pressure and thyroid hormone levels when a cat has this heart-scan appearance before deciding whether it represents primary HCM. [1]

Yes. Some cats have HCM without showing any outward signs.

Vets describe cardiomyopathy without clinical signs as stage B. A cat can therefore seem well even though heart disease is present. [1]

Yes. A cat can have HCM without an audible heart murmur.

A murmur can be a clue, but it is not present in every affected cat. HCM can also occur in young cats and females, although it is more often associated with older male cats and louder murmurs. [1]

When cardiomyopathy causes signs, laboured breathing is the most common. Some cats instead hide or lose interest in food.

Many cats with cardiomyopathy, particularly HCM, have no obvious history of illness before it is found. [1]

HCM can lead to congestive heart failure, an arterial blood clot or sudden death.

Some cats tolerate the condition well and have a normal life expectancy, while others develop one or more serious complications. [1]

An echocardiogram performed by a veterinary cardiology specialist is the test of choice for diagnosing cardiomyopathy in cats.

Even specialists can sometimes find it difficult to distinguish one form of cardiomyopathy from another on the scan. [1]

For most average-sized cats, heart-wall measurements below 5 mm are considered normal, while measurements of 6 mm or more indicate thickening.

A result between 5 mm and 6 mm is a grey area. Vets interpret it alongside the cat's body size, family history and other findings on the heart scan. [1]

No. NT-proBNP testing is not reliable enough to tell a normal cat from one with mild or moderate HCM.

A normal result therefore does not, by itself, exclude those milder forms.

NT-proBNP reflects stretch and stress on the heart and can be useful as a screening test. [1]

Veterinary management of feline cardiomyopathy depends on the cat's clinical stage and risk of complications.

There is no single plan for every cat: the consensus guidance separates management recommendations by stage. [1]