Cat heart murmur: symptoms and causes plus video of ultrasound testing

It is worthwhile to have a quick look at the causes before setting out cat heart murmur symptoms as it helps to understand the symptoms. It is important to state that I am not a veterinarian. I do know a lot about cats and cat health. The latter information has all been gleaned from reference books and studies. The former information has been acquired through direct experience of many years of caregiving, together, of course, with reading many reference books. Therefore, this article should be read in that light and in the knowledge that there is no substitute for seeing a veterinarian. That said, a well-informed cat caregiver at a veterinary clinic is an asset.

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A cat with heart disease
A cat with heart disease. Photo in public domain.

Jan 2008: Tippy, above, had heart disease. He was put to sleep and sadly missed. He had blood clots, one of the signs of either type of cardiomyopathy described below. I’d like to dedicate this page to him.

What are feline heart murmurs?

Feline heart murmurs are the sound of the blood flowing through the heart. Sometimes it is simply what is to be expected. These are called ‘functional’ murmurs and are not indicative of a health problem. In other words, the sound is that of the heart functioning normally.

Feline heart murmur causes
Feline heart murmur causes. Chart: MikeB

However, heart murmurs are serious when due to feline cardiomyopathy and birth defects. For example, an FIV infected mother can give birth to kittens who have birth defects (congenital problems). Hypothyroidism can also cause heart murmurs (see below).

Heart murmurs can be graded from 1 – 6 (6 is the most serious) (

Sometimes the murmur can be bad enough to the point where it can be felt as a buzzing or vibration over the area of the heart. This is called a thrill and is a serious heart condition and one of the cat heart murmur symptoms.

Heart muscle function is reduced when a cat has cardiomyopathy. There are two forms: hypertrophic and dilated. Cat heart murmur symptoms are different in each case.

Hypertrophic cardiomyopathy (HCM)

The walls of the heart (the ventricles) became thickened but weaker. The heart becomes less elastic. I have made some other posts in relation to this disease concerning the Bengal cat breed: HCM in Bengal Cats (this link opens in a separate window and at a blogger subdomain site).

As feline cardiomyopathy causes heart murmurs the symptoms of this diseases will provide a clue as to whether the cat has a heart murmur. The murmur can be detected by a veterinarian with a stethoscope.

However, early symptoms of HCM are apparently vague. It may not be noticed as cats can adapt to the change. Coughing is not usually a sign of heart disease.

Dilated cardiomyopathy

This is a much quicker onset and progresses over several days. The heart muscle loses tone. One cause is lack of taurine, an essential ingredient in a cat’s diet (see Homemade Cat Food and Bengal Cats and Taurine – both these links open in a new window).

RELATED: What are the symptoms of taurine deficiency in cats?

The symptoms of dilated cardiomyopathy are clearer and as follows:

  • laboured breathing when resting
  • sitting with head & neck extended straining for breath
  • extremities (ears and feet) are cold
  • pulse rapid
  • heart murmur
  • loss of appetite
  • weight loss
  • weakness

Feline Hyperthyroidism

As a form of dilated cardiomyopathy can be caused by feline hyperthyroidism the symptoms of hyperthyroidism may be an indication that the cat has a heart murmur as well. Hyperthyroidism is caused by an excess of the hormone thyroid running through the veins. It occurs in older cats and may be an underlying disease. The symptoms are:

  • restlessness
  • irritableness
  • pacing
  • hungry and thirsty
  • weight loss
  • vomiting
  • increased amount of feces

Although symptoms may be masked by other illness in an old cat.


Ultrasound testing can detect heart disease (and its severity) and kidney disease. See this video taken of a person using mobile equipment to detect for HCM in purebred show cats at a cat show in Oklahoma, USA. It was not expensive by the way. As I remember about $80. The video was made by me. This was a mobile testing facility.

Heart Murmurs and Age

Cat heart murmur symptoms need not mean a shorter life. Having read forums etc. it seems that a decent and sometimes a long life can be had by a cat with a heart murmur. It clearly depends on the severity of the heart disease. Cats that have heart murmurs should not be written off.

From Cat Heart Murmur Symptoms to Cat Health Problems

Sources: Pet Health Blog (vets’ input), Cat Owner’s Home Veterinary Handbook, as stated in text, own experience.

Postscript: this page has been refreshed and checked with some added improvements as at December 29, 2021. It’s been republished at that date to bring it forward.

2 thoughts on “Cat heart murmur: symptoms and causes plus video of ultrasound testing”

  1. My female long haired tabby Daisy has had a grade 5 heart murmer,since it was found as 8week old kitten checkup,by vet,he thought she would only live less than a year! Thankfully she is now 4years6months approx.she has learned to pace herself,although I can tell it does effect her breathing at times,because she opens and closes her mouth,her purr can sound very noisy,b it rattly at times but as yet she’s not needed meds!what concerns me is a neighbour has installed an ultrasonic cat deterrant on top of their boundary fence,my cat always daily crosses top of fence to go in vegitation behind it! Does anyone know if these deterrants could harm a cat with a severe heart murmer? Would be grateful for any info!

    • Hi Suzanne. Thanks for commenting. My first impression (and I am pretty sure I am correct) is that the ultrasonic device will not harm you cat. It just creates high frequency sound. It should be okay. Make sure that the person does not harm your cat though! Good luck. I’ll check some more today and get back if I am wrong.


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