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Heart Murmurs in Cats

A heart murmur is an abnormal sound heard when listening to the heart with a stethoscope. It is caused by turbulent blood flow and high velocity. A veterinarian cannot tell the cause of the heart murmur just by listening to the heart. If a murmur is heard, it is recommended that tests are run to determine the cause of your cat’s heart murmur. Even without any symptoms, cats can have serious underlying heart disease.

Common Causes of Heart Murmurs in Cats

  • Innocent Kitten Murmur: Kittens may have a quiet heart murmur that resolves by 5 months of age. If the murmur goes away, there is no need to investigate the cause of the heart murmur. If the murmur persists after 5 months, a full work up is warranted. We will monitor your kittens heart murmur at every visit and let you know if any testing needs to be done.

  • Physiologic or Flow Murmur: This is a benign cause of a heart murmur and there is no structural heart disease present.

  • Congenital Heart Disease: Cats can be born with abnormal hearts and we may hear a heart murmur in these cases. If your kitten has a heart murmur and is over 5 months old, or the murmur is very loud, your vet will recommend investigating the cause of the murmur.

  • Systemic Disease: Other disease can cause heart murmurs, including high blood pressure, hyperthyroidism, and anemia.

  • Heart Disease: The most common heart disease seen in cats is Hypertrophic Cardiomyopathy, or HCM. HCM can lead to clinical symptoms, like congestive heart failure, blood clots, and lethargy.

Breeds with Increased Incidence of Heart Disease

Although any breed can develop heart disease, it is found at higher rates in certain breeds of cats.

  • Maine Coon
  • Norwegian Forest Cat
  • Ragdoll
  • Sphynx
  • British or American Shorthair
  • Devon Rex
  • Persian
  • Oriental Breeds

Diagnostic Tests for Heart Murmurs

If your veterinarian hears a heart murmur for the first time, we may recommend that your kitty return for a recheck to see if we hear the murmur again. Some cats may get a heart murmur from stress. If your veterinarian hears the murmur consistently, they will recommend further diagnostics.

  • Blood Tests: A full profile including a blood count, thyroid, chemistry screen, and urinalysis will be run. This will help your veterinarian rule out systemic disease (anemia, thyroid disease, etc.) that can cause or contribute to a heart murmur. In addition, a special blood test called Cardiopet proBNP may be recommended. This test looks at an enzyme that is present when there is significant stretch of the heart muscle cells. This test is good for screening cats for significant disease, but it still will not tell us what type of heart disease is present. We will recommend running this test at regular check ups to monitor for any changes.

  • Blood Pressure: Your veterinarian will check a blood pressure to rule out hypertension.

  • ECG: An ECG may be done to look for arrythmias or other changes in the heart.

  • Chest X-Rays: X-rays can help your veterinarian screen for changes like congestive heart failure and other diseases, but it is not very helpful in diagnosing hypertrophic cardiomyopathy.

  • Echocardiogram: An echocardiogram is an ultrasound of the heart. This is the test of choice to determine the cause of your cat’s heart murmur.


Heart murmurs are heard by your veterinarian during your cat’s exam. If your veterinarian hears a new heart murmur, they will guide you on the recommended work up for your kitty. Cats with heart murmurs can live long, healthy lives, but it is important to determine the cause of the murmur. Cats with hypertrophic cardiomyopathy may need medication. Most cats will need periodic follow up, including exams, blood tests, and even echocardiograms

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