Heart murmurs in cats

A heart murmur is an abnormal noise that can be heard when listening to a cat’s chest with a stethoscope. Heart murmurs affect cats of any age, but are most common in middle aged and older cats.  An ultrasound scan of the heart is usually the best way to know what is going on.

Many heart murmurs in cats are ‘functional’, meaning they are due to stress or other factors. A murmur is usually caused by turbulence, meaning blood isn’t flowing through the heart as smoothly as it should. Others can be due to problems with the heart itself, the blood pressure, or other diseases. How loud a murmur is does not always reflect the seriousness of the problem. Cats are very good at hiding signs of heart disease and when in doubt it is safer to check what is going on.


What to do

How to tell if your cat has a heart murmur

A stethoscope and a trained ear are usually needed to detect a murmur, so this is something a vet will detect during an examination. Where a murmur is caused by a heart problem, you may first notice signs of heart disease. This includes:

  • Sleeping or hiding more
  • Eating less and losing weight
  • Not wanting to play
  • Struggling to jump or climb or other signs of weakness
  • Tiredness after minimal exercise
  • Intermittent coughing
  • Fast or laboured breathing
  • Having a wet or runny nose
  • Fainting
  • Sudden pain and loss of use of their back legs
  • Stunted growth (kittens)



Why does my cat have a heart murmur?

Heart murmurs in young kittens:

  • Small openings in the heart allow blood to flow in the wrong direction
    • These openings form naturally as the heart develops in the womb but should close before or soon after birth
  • Abnormal development of large blood vessels in the chest
  • Occasionally due to inherited (genetic) problems
  • More commonly an unfortunate mischance

Cats of all ages:

  • Diseases of the heart muscle, called cardiomyopathy
    • The heart is a muscular pump for blood.
    • Changes in the thickness of the heart muscle affect how blood flows through the heart
    • A warning heart murmur is often present before other symptoms develop
    • Most common in adult and older cats
    • More common in certain breeds
  • High blood pressure (hypertension) and hyperthyroidism
    • Cause irregular blood flow through the heart and largest blood vessels
  • Anaemia or low numbers of red blood cells
    • Reasons for anaemia include infections or long-standing diseases
  • Diseases of the heart valves.
    • Heart valves control the direction of blood flow through the heart, making sure it’s a one-way system
    • Diseases of heart valves are not common in cats


When to worry

When to worry about a heart murmur in your cat

When the murmur is first detected, your vet will discuss with you a plan that will depend on the type of murmur and whether other signs are present.

  • Some types of murmur are more concerning and will need to be investigated straight away
  • The heart murmur may change from one examination to the next. In a recent study no disease was found in 56% of cases.
  • Many kittens also have mild murmurs during their growth that disappear with age.
  • If a murmur is consistently present on repeat examinations or any other concerns are present, further testing is advisable.

Preventative treatments, such as anticoagulants or blood pressure medication, may prevent severe complications if started at the right time.


Can I prevent a heart murmur in my cat?

  • The best way to prevent heart murmurs in kittens is not to breed cats if others in their close family tree were born with or developed heart problems.
  • Good quality and balanced nutrition for the mum also helps prevent developmental issues in the kittens.
  • Balanced nutrition remains important for heart health throughout the cat’s life, especially when it comes to having appropriate levels of the essential amino acids the heart needs.
  • It is suspected that chronic dental disease may allow bacteria to get into the blood and settle in the heart valves. Good dental care may prevent some heart problems.
  • Good flea and tick prevention helps reduce the risk of infections that cause anaemia.



What to look out for in a cat with a heart murmur

Please speak with a vet if your cat has been diagnosed with a murmur and develops any of the following symptoms. You can speak to a vet in the Joii app if you’re unsure.

  • Sleeping or hiding more
  • Tiredness after minimal exercise
  • Intermittent coughing
  • Fast or laboured breathing
  • Having a wet or runny nose
  • Fainting
  • Sudden pain and loss of use of their back legs


Home treatment

How can I help my cat with a heart murmur?

Cats are very good at hiding illness. In the early stages of heart disease or hypertension, they may be able to cope with the symptoms through adjustments to their habits. This often goes unnoticed. The disease may then appear when a sudden, severe complication arises. This is why regular checks and early treatment are important.

When heart disease is present:

  • Ideally, keep your cat indoors
  • Keep your cat cool in hot weather
  • Avoid active pouncing or chasing games
  • Minimise stressful events like travel, catteries or household upheavals
  • Provide coping mechanisms when stress is unavoidable, such as safe and accessible hiding places or pheromone diffusers

Monitoring how quickly your cat is breathing at rest is an excellent way to keep track of changes in heart function.

  • Wait until your cat is relaxed and  sleeping
  • Count how many times they breathe in and out in one minute (one cycle in and out = one breath)
  • Most cats take between 15-40 breaths per minute
  • Keep a daily record of your cat’s breathing habits so you can check for increases over time
  • An increase in breathing rate can be an early warning of poor blood flow and fluid build up in the lungs
  • Sudden changes to breathing should be discussed with a vet straight away.

Phone apps are available to help you to monitor your cats breathing rate effectively at home.

Vet treatment

What is the vet treatment for heart murmurs in cats?

Before deciding on the best approach to treatment, your vet may recommend blood pressure checks and blood tests to check for other diseases. An ultrasound with a specialist will help determine the cause of the murmur and evaluate any heart disease present.

Treatment will depend on the cause of the murmur.

  • Some heart defects in kittens require complex operations at a specialist veterinary hospital
  • High blood pressure can often be managed with medication.
  • Hyperthyroidism can sometimes be cured with surgery or radiation therapy but often is a long-term condition managed with medication.
  • Chronic disease of the heart muscle can’t be reversed or cured but daily medication may improve quality of life and prevent serious complications. Treatment is usually lifelong.
    • Regular check ups and blood tests allow your vet to monitor your cat’s progress and adjust medication when needed. Over time some medicines will need to be changed or added in to keep your cat’s quality of life as good as possible.
    • Anticoagulant medicines reduce the build-up of blood clots in the heart and prevent them from causing blockages in other parts of the body.
    • Diuretics (‘water tablets’ or injections) help to remove fluid build-up in the lungs.
  • Fluid build-up around the lungs will need to be removed by placing a special drain in the chest. This helps them to breathe more easily and feel much better.
  • Other medications may be used for specific conditions.

Often ultrasound scans will need to be repeated periodically to see if the disease is progressing and treatment needs to be adjusted.


Are some cats more at risk of heart murmurs than others?

Certain breeds of cats have a higher risk of developing heart murmurs and heart disease.

  • Maine Coon cats
  • Persians
  • American and British Shorthairs
  • Siamese cats

Other causes of heart murmur in cats

Endocarditis (infection of a heart valve) is rare in cats. Infection and inflammation result in the heart valve(s) becoming misshapen. A murmur develops when the damaged valve leaks. Cats with endocarditis will be very sick.

Pregnancy may cause a temporary heart murmur, but this doesn’t reflect any health problem and should disappear when the kittens are born.

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