Heart murmurs in dogs

A heart murmur is an abnormal noise that can be heard when listening to a dog’s chest, usually with a stethoscope. Heart murmurs are most common in older dogs but can also happen in puppies, and are often the first sign of a serious heart problem.

The murmur is caused by turbulence, meaning blood isn’t flowing through the heart as smoothly as it should. How loud a murmur is does not always reflect the seriousness of the problem. An ultrasound scan of the heart is usually the best way to know what is going on and is also useful for monitoring.


What to do

What should I do about my dog’s heart murmur?

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. An ultrasound scan and other tests allow us to know exactly what is going on in the heart and also how it is coping, which is the best way to guide treatment decisions.



Why does my dog have a heart murmur?

Adult dogs

  • Commonly a heart valve (a little gate that makes sure the blood is flowing in the right direction) is not closing properly and is letting blood leak backwards.
  • These changes can happen slowly with aging, but may sometimes be due to a low-grade infection in the valve.
  • This may not be causing any problems when first detected but can cause heart failure over time.


  • Mild murmurs happen because of differences in blood flow during development and these will disappear as the puppy grows.
  • Sadly, puppies can also have a murmur because a valve does not open properly or because of a hole connecting parts of the heart that should be separated. The best chance for these puppies is if the problem is addressed before more symptoms appear.


When to worry

When to worry about a heart murmur in your dog

  • Some types of murmur are more likely to be due to serious disease and your vet will recommend tests straight away.
  • A study has shown that about 28% of puppies have a murmur that will cause no issues and disappears by 6 months of age. When one of these is suspected, your vet will recommend regular monitoring.
  • In adult dogs, murmurs are almost always associated with heart disease. Sometimes this will progress very slowly, while in others the disease may already be quite advanced.

Please speak with a vet straight away if your dog has been diagnosed with a murmur and develops any of the following symptoms:

  • Shortness of breath
  • Laboured breathing
  • Tiredness after minimal exercise
  • A swollen abdomen
  • Coughing
  • Fainting



Can I prevent heart murmurs in my dog?

  • The best way to prevent heart murmurs in puppies is not to breed dogs if others in their close family tree were born with heart problems.
  • Good quality and balanced nutrition for the mum also helps prevent developmental issues in the pups.
  • Balanced nutrition remains important for heart health throughout life.
  • 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.



Things to look out for if your dog 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. In very severe cases you can hear the murmur by placing an ear against your dog’s chest. In these cases, you can even feel the reverberations of the murmur through the chest wall by placing your fingertips or palm over the heartbeat.

If a murmur goes undetected, you may instead spot signs of heart disease, such as:

  • Tiredness/sleeping more
  • Inability to cope with exercise
  • A dry cough that doesn’t go away, usually noticed more in the evening
  • Excessive panting or fast/laboured breathing
  • Fainting


Home treatment

How can I help my dog with a heart murmur?

Heart murmurs lead to heart disease over time. Many adult dogs will have a completely normal life for a long time, but once functional changes start to happen in the heart, treatment is very important. This can reduce symptoms and sometimes slow down the progression of the disease. This is why regular checks and early treatment are important.

Once symptoms develop, it is advisable to:

  • Avoid intense exercise, especially in hot weather.
  • Monitor how quickly your dog is breathing at rest. This is an excellent way to keep track of changes in heart function
    • Wait until your dog is relaxed and  sleeping
    • Count how many times they breathe in and out in one minute (one cycle in and out = one breath)
    • Most dogs take between 15-30 breaths per minute
    • Keep a daily record of your dog’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


Vet treatment

What is the treatment for heart murmurs in dogs?

The best approach to a heart murmur depends on what is causing it and whether there are any other changes to the heart.

  • Your vet may recommend an ultrasound with a specialist or other tests to get more information.
  • Some problems in puppies can be completely cured with surgery or other advanced procedures, but these require referral to a specialist vet. Medication may help stabilise the condition until treatment can be attempted.
  • Chronic changes in older dogs cannot be reversed, but medication may improve heart function and sometimes slow down the disease.
  • In most cases treatment should be started after the heart function starts to change, but before obvious symptoms develop. Heart scans help find this window.
  • Once started, treatment is usually for the rest of the dog’s life, but some medications may need to be adjusted over time depending on progression of disease and development of complications.
    • An Inodilator can be used to improve blood supply to the heart itself as well as heart muscle function
    • ACE inhibitors help avoid congestion and lower blood pressure
    • Diuretics (water tablets) help remove fluid that is accumulating in the lungs, chest or abdomen
    • Other medications (such as Digoxin or Sildanefil)  are used more rarely and for very specific conditions.



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

Congenital heart problems have a strong genetic component. Breeds commonly affected are:

  • Boxer
  • French Bulldog
  • English Bulldog
  • Newfoundland
  • Rottweiler
  • Golden Retriever
  • Chihuahua
  • Cavalier King Charles Spaniel
  • Dobermann
  • Miniature Pinscher
  • Cocker Spaniel
  • Yorkshire Terrier
  • Border Collie
  • Dachshund
  • Dogue de Bordeaux
  • Bull Terrier

Chronic valve disease can happen in any breed, but Cavalier King Charles Spaniels tend to develop it at earlier ages. Other breeds that are commonly affected are:

  • Miniature poodles
  • Cocker spaniels
  • Miniature schnauzers
  • Dachshunds
  • Chihuahuas
  • Many small terrier breeds

Other causes of heart murmur in dogs

Dogs with disease of the heart muscle, such as dilated cardiomyopathy, may sometimes have a murmur as well, but this is less common than other causes of murmurs.

Anaemia and other problems that make the blood thinner can cause a temporary murmur to appear. This goes away once the blood is back to normal.

High blood pressure due to disease or exercise can cause an intermittent heart murmur, as can fever and severe infections elsewhere in the body.

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