Heart Murmur in Cats

Heart Murmur in Cats

Heart murmurs can sound very scary if your vet has just told you that they’ve heard one while listening to your cat’s chest and abdomen with a stethoscope. But a heart murmur in cats doesn’t always mean a dire situation and in fact, some heart murmurs are very common.

Heart murmurs are caused when the blood flow around the heart, namely the large vessels exiting from the heart, becomes increasingly turbulent and forces pressure and an abnormal heart rate. That increase of pressure within the blood flow is so great that it actually produces a noise, which is known as a heart murmur.

Once the vet has detected a murmur, they will grade it according to what they heard. The grades of heart murmurs range from Grade I, which is the most minor, to Grade VI, the most severe and worrisome. The grade of the murmur depends on how loud it is and where it was heard on the body. But a loud murmur doesn’t always mean that it’s going to have severe consequences on the heart. Some heart conditions don’t produce any murmur at all but are quite dangerous, while other minor underlying condition can produce a very loud murmur with little to no effects.

The grades of heart murmurs are as follows:

  • Grade I – can barely be heard through a stethoscope
  • Grade II – can be heard, softly but easily, with a stethoscope
  • Grade III – a very common grade of murmur, this murmur has “intermediate loudness”
  • Grade IV – a murmur that can be heard on both sides of the chest, can seem to radiate, and is quite loud
  • Grade V – can be heard when stethoscope is very gently placed on the chest, can also be felt through the walls of the cat’s chest when a hand is laid over it
  • Grade VI – can be heard, sometimes without a stethoscope, and can definitely be felt when hand is placed over it

In addition to the grades of the murmur, the vet may also speak to you about the configuration of the murmur or rather, its rhythm. This configuration is typically classified into one of three categories:

  • Plateau murmurs – loudness is consistent and uniform
  • Crescendo murmurs – start soft and get louder
  • Decrescendo murmurs – start loud and get softer

Sometimes, especially with the mildest forms of heart murmurs, cats won’t display any symptoms of having one at all. However, if the murmur is due to structural heart disease or congestive heart failure, the most common symptoms will be coughing, weakness, and an inability to exercise.

Causes of a Heart Murmur in Cats


Heart murmurs are typically caused by an underlying heart condition but there are other causes of heart murmurs, too. The most common are:

  • Murmurs are often heard in young kittens under the age of six months old and typically go away within a couple of months of being heard. These are called “innocent” murmurs.
  • “Physiological” murmurs that can randomly be heard as blood is pushing through the existing blood vessels but don’t have any significance.
  • Abnormal valves causing an abnormal blood flow between them.
  • Dilated vessels or diseased valves between the chambers of the heart.
  • Anemia.
  • Hyperthyroidism.
  • Heartworm.

Diagnosing and Treating Heart Murmurs in Cats

After listening to the heart and chest through a stethoscope, as well as doing a physical examination of the area, your vet will identify the heart murmur, but that’s not the complete diagnosis. In order to provide that diagnosis, the vet will have to listen carefully to the murmur while trying to detect and differentiate between different sounds. The sounds of a murmur can range from split sounds, ejection sounds, galloping sounds, and clicking sounds, and each sound will help the vet determine which type of murmur your cat has, and how to treat it.

After a physical examination and listening with their stethoscope, the vet will most likely also want to perform other tests to eliminate or determine the underlying cause of the heart murmur. These can include but are not limited to x-rays, a Doppler test, and echocardiography. Blood samples may also be taken to determine the total blood count. This particular test can be helpful when detecting murmurs due to anemia.

Treatment for heart murmurs can be very easy and in fact, require little to no treatment at all. This is especially true in the case of the innocent murmurs found in kittens. If a heart murmur is detected however, the vet will also likely recommend that the cat come back every few months to monitor the murmur and document any changes. When the murmur is due to something more serious, treatment will depend on treatment for the underlying condition.

A heart murmur in cats can sound very frightening upon first hearing that your cat has one. However, many heart murmurs are completely harmless with some even dissipating in their own time. It’s important to keep calm and know that even when a murmur does indicate an underlying problem with the heart, most can be treated, helping get rid of the condition and the murmur all at the same time.



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I've been a dog lover since the day I was born but it's the current four legged love of my life, Phoebe who inspired me to create the Munch.Zone.

We moved together from Israel to New York in 2013, love hiking together, and never pass up a trip to the dog park. Watching her over the years sparked so many questions about dog behavior and health needs, and it wasn't always easy to find answers. Thus, the Munch.Zone was born.

On any given day you'll find me watching Netflix originals, eating popcorn, and thinking about how to get into house flipping.

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