Heart murmurs in cats – signs and vet care

Updated 2026-09-30 · 2 sources

Based on: PDSA, International Cat Care (iCatCare)

Book a vet visit

Book a vet appointment if you think your cat has this – a vet needs to confirm it and plan the treatment. A heart murmur is a whooshing sound caused by abnormal blood flow inside the heart.

What to do now

What you can do now

Contact your vet.
Note when it started, how often it happens and what else you see.
Take a photo or short video to show the vet.
Keep fresh water available.
Let your cat rest somewhere calm.

Don't

Do not give any human medicine.
Do not wait if it gets worse.

What it is

A heart murmur is a whooshing noise caused by abnormal blood flow inside the heart.^[1] Not all heart murmurs are problematic; some innocent flow murmurs are harmless.^[1]

Signs

Lethargy or tiredness
Pale gums
Abnormal breathing or increased breathing effort
Panting or open-mouth breathing
Weakness
Reduced appetite
Coughing
Collapse
Weight loss
Swollen abdomen

Causes and risk factors

Heart disease
Anaemia
High blood pressure
Hyperthyroidism
General illness
Pregnancy
Innocent flow murmurs

How a vet finds out

Physical examination
Blood tests
X-rays
Ultrasound
ECG
Echocardiogram

How vets treat it

Medication may be considered, depending on the underlying cause and heart-scan results.
Some cats with heart disease may not need specific treatment.

What the experts say

“Overview. A heart murmur is a whooshing noise caused by abnormal blood flow inside the heart. There are a few different conditions that can cause a heart murmur in a cat. Not all heart murmurs are problematic, some (such as innocent flow murmurs) are harmless.”
— PDSA [1]

“This very much depends on the underlying cause of the murmur. Cats with heart disease may not need specific treatment, depending on the results of the heart scan, while others may benefit from medication.”
— International Cat Care (iCatCare) [2]

If your pet is struggling to breathe, has collapsed, is having a seizure or can't stand up: go to the nearest vet now.

Not sure how serious it is?

OkPaw asks a few quick questions about your pet and tells you in 30 seconds whether it can wait. Free on Google Play for Android.

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Common questions

What is a heart murmur?

It is a whooshing noise caused by abnormal blood flow inside the heart.^[1]

Are all heart murmurs harmful?

No. Some, such as innocent flow murmurs, are harmless.^[1]

How does a vet hear a murmur?

A vet can hear it when listening to your cat’s heart with a stethoscope.^[2]

Sources

How this page was made: written with the help of AI from the sources below, then checked claim by claim against those sources. Urgency levels follow OkPaw’s fixed safety rules. It is guidance, not a diagnosis. How we write our pages

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