What does it mean when we diagnose a heart murmur in your cat during a consultation?

What is a murmur?

Firstly, cat heart murmurs don’t always mean something bad!
A murmur just indicates that there is blood flow turbulence somewhere in the heart or in the great vessels that are leaving the heart. This can result from many different things. Sometimes the murmur may be a sign of a serious problem. However, the problem can often be treated, with the cat having many wonderful, comfortable years ahead of him.
A kitten, for instance, may have what is known as an “innocent” murmur that he outgrows. In fact, it’s very common for kittens to have a soft murmur in the first months of life!
Older cats may occasionally develop soft heart murmurs often due to anaemia, fever, or other systemic illness. An adult cat with a murmur might also have a disease of the heart muscle, called cardiomyopathy. The most common type of cardiomyopathy in cats is hypertrophic cardiomyopathy, which is a thickening of the heart muscle. That prevents the muscle from fully relaxing, so limiting the amount of blood the heart can pump.
The loudness of the murmur depends on where the muscle thickens. Murmur or not, cardiomyopathy often leads to congestive heart failure and may need to be treated with medicine to slow the progression of the disease, and this can be very effective! Appropriately treated cats can live a long time, often years, with a good quality of life.

Are there different types or severity of murmurs?

Murmurs are graded on a scale of one to six for loudness or intensity. A grade one is so quiet that even an experienced listener can only hear it after a few minutes in a quiet room. A grade six, on the other hand, can often be felt on the side of the chest wall.

What should I expect if my cat has a murmur?

Not all heart murmurs call for immediate follow-up testing to find the cause. For a young kitten with a low-grade murmur, we can normally just wait and see if he grows out of it. But as a general rule for adult cats, an echocardiogram, or ultrasound of the heart is highly recommended. A chest X-ray and a blood test, called NT-proBNP, are often used in diagnosing heart disease and assessing the need for further diagnostic tests.

Remember that just as not all murmurs are signs of heart disease, lack of a murmur does not automatically mean heart disease is not present. Another way of putting it: being told your cat has a murmur might be concerning, but it’s better to know so we can perform tests to determine whether heart disease is present, rather than to allow an undiagnosed disease to silently progress.

We hope your cat is found to be happy healthy and heart disease-free! But you can always talk to us if you have any worries.