When a vet hears a murmur in a cat that seems perfectly healthy, owners understandably assume the worst. The research on this is unusually clear, and it cuts both ways: most murmurs in healthy-looking cats are harmless, and some cats with real heart disease have no murmur at all.
So a stethoscope can raise the question but can’t answer it. This page explains why, what actually answers it, and why it’s worth finding out even in a cat with no symptoms.
What the Studies Found
The largest look at this is the CatScan study, published in 2015 in the Journal of Feline Medicine and Surgery. Researchers examined 780 apparently healthy cats in UK rehoming centres with both a stethoscope and an echocardiogram:
- About 41% had a heart murmur.
- About 70% of those murmurs were judged to be functional, meaning not caused by heart disease.
- Hypertrophic cardiomyopathy (HCM), the most common heart disease in cats, was found in about 15% of these apparently healthy cats.
- A murmur’s ability to predict HCM was modest: depending on age, only roughly 18–43% of cats with a murmur turned out to have HCM. Murmurs were more likely to mean disease in older cats.
A smaller study of 32 healthy-looking pet cats with murmurs (Nakamura and colleagues, 2011) found echocardiographic evidence of heart disease in 53%. The other 47% had murmurs from causes that weren’t heart disease.
Read together, a murmur in a healthy-looking cat is close to a coin flip. A cat without one isn’t guaranteed a healthy heart either.
Why Cats Are So Different From Dogs
In dogs, the common adult heart disease is a leaking valve. The leak itself makes the murmur, so a louder murmur generally tracks with more advanced disease. (Our page on dog heart murmurs covers that story.)
In cats, the common disease is a thickening of the heart muscle itself, and the sounds it makes are less predictable. Cat murmurs also often come and go with heart rate and excitement. A cat that is stressed at the clinic can have a murmur that disappears when it is calm at home. Other conditions — an overactive thyroid, high blood pressure, anaemia — can also produce murmurs, or thicken the heart muscle, without primary heart disease.
Veterinary cardiology guidance is explicit on both points: a murmur raises suspicion but isn’t diagnostic, and the absence of a murmur does not exclude heart muscle disease.
What Actually Answers the Question
| Test | What it tells you | Typical cost |
|---|---|---|
| NT-proBNP blood test | Screening: an abnormal result is an indication for an echocardiogram | Considerably less than an echo; ask your clinic |
| Echocardiogram (heart ultrasound) | The definitive test: shows wall thickness, chamber size and function | About $400–$1,200; many routine studies $600–$850 |
| Blood pressure and thyroid test (older cats) | Checks for conditions that can mimic or drive heart changes | Often part of senior bloodwork |
Chest X-rays, so useful in dogs, are much less sensitive for early heart muscle disease in cats. They become more useful once heart failure is suspected.
Many vets use the NT-proBNP test as a first step when an echocardiogram isn’t immediately practical. A normal result is reassuring, and an abnormal one is the indication to go on to an echocardiogram.
Why It’s Worth Finding Out in a Cat With No Symptoms
Cats hide heart disease extremely well. Often the first sign isn’t tiredness or a cough but one of two emergencies:
- Congestive heart failure: fast or laboured breathing, sometimes with the mouth open.
- Arterial thromboembolism, a blood clot, often lodging where the aorta splits to the back legs. It causes sudden back-leg weakness or paralysis, cold back feet and severe pain.
Knowing in advance changes what you can do. Under the staging system cardiologists use, cats whose disease has enlarged the left atrium, a higher-risk stage called B2, are typically started on clopidogrel, a medication to reduce the risk of clots. Cats at the earlier stage, B1, usually need no heart medication, just treatment of any thyroid or blood pressure problem and periodic rechecks.
There’s also a practical reason. If your cat has a murmur and an anaesthetic is coming up, for a dental cleaning for example, ask your vet whether screening first makes sense. Heart disease can change how anaesthesia and IV fluids are managed.
Which Cats Are Higher Risk
HCM can occur in any cat, including mixed breeds, which make up most cases simply because they are most cats. Certain breeds are recognised as predisposed, including Maine Coons, Ragdolls, British Shorthairs, Sphynx and Persians, and genetic tests exist for specific mutations in Maine Coons and Ragdolls. For predisposed breeds, cardiology guidance recommends screening echocardiograms even without a murmur.
What to Watch at Home
The most useful daily check is the sleeping breathing rate. Count your cat’s breaths while she is asleep and not purring:
- About 15–30 breaths a minute is typical.
- Consistently above about 30 is the point to recount and call your vet.
Our Sleeping Respiratory Rate Counter runs the 30-second count and keeps a log you can show your vet.
Go to an emergency vet for open-mouth breathing, laboured breathing, collapse, or sudden weakness, dragging or crying in pain in the back legs.
Frequently Asked Questions
Does a heart murmur mean my cat has heart disease? Not necessarily. In the CatScan study of 780 apparently healthy cats, about 41% had a heart murmur, and around 70% of those murmurs were judged to be functional rather than caused by heart disease. A smaller study of healthy-looking cats with murmurs found heart disease on ultrasound in 53% of them. A murmur in a cat is a reason to find out, not a diagnosis.
Can a cat have heart disease without a murmur? Yes. Veterinary cardiology guidance is explicit that the absence of a murmur does not rule out cardiomyopathy, and some cats with heart muscle disease sound completely normal. In the CatScan study, hypertrophic cardiomyopathy was found in about 15% of apparently healthy cats, a reminder that a quiet stethoscope is not a clean bill of health.
How do vets find out if a cat’s murmur is serious? An echocardiogram (heart ultrasound) is the test that gives a definitive answer. A blood test called NT-proBNP can be used as a screening step: an abnormal result is an indication for an echocardiogram. Chest X-rays are less useful for spotting early heart muscle disease in cats than they are in dogs.
How much does a cat echocardiogram cost? Published price ranges run from about $400 to $1,200, with many routine studies falling around $600–$850. The NT-proBNP screening blood test costs considerably less, which is why some vets use it first to decide whether an echocardiogram is needed.
What are the warning signs of heart disease in cats? Cats often show nothing until heart disease is advanced. Signs to act on include a sleeping breathing rate consistently above about 30 breaths a minute, breathing with the mouth open, hiding or reduced activity, and sudden weakness, dragging or pain in the back legs, which can be a blood clot. Open-mouth breathing and sudden back-leg weakness are emergencies.
Related Articles
- Sleeping Respiratory Rate Counter — the daily home check
- Dog Heart Murmur: Why Heart Size Matters More Than the Grade
- Cat Hyperthyroidism Treatment Cost — a common cause of murmurs and heart changes in older cats
- How Much Does a Cat Vet Visit Cost?