Heart Murmurs In Dogs: What Does It Mean For Your Pet?


A devoted pet parent, pet store manager and animal shelter volunteer. Read more about me here.

Our pets are like our family; all pet owners know that. No, scratch that. Our pets ARE family. We never want anything bad to happen to them - and if something does happen, we want to react adequately.

So, your pooch has been diagnosed with a heart murmur, or you think they might have it - what does it mean? What's the prognosis?

Do heart murmurs affect their quality of life, does it seriously affect your dog's health, will they feel any discomfort? Can you walk a dog with a heart murmur?

I'm sure these - and many other - questions might be bubbling up in your mind.

Worry not; I'm here to answer all of your burning questions and hopefully ease your mind. So, if that's what you're looking for today - keep reading!

What Is A Heart Murmur?

You might've heard this term being used when talking about heart conditions in humans - but did you know it could also affect dogs? Well, unfortunately, it can, and it doesn't differ much from when it's found in people.

One way to recognize it yourself is by hearing an abnormal sound that occurs when blood flows fast across the dog's heart valves - a sound that could be described as "swooshing."

But, what is it actually? 

Well, first and foremost, I want to point out that a heart murmur is not a disease, nor does it indicate that your dog has heart disease. What it should be seen as is a signal to investigate further. It can be a red flag and definitely shouldn't go unchecked by a vet - but you certainly shouldn't panic, either.

A heart murmur alone won't make your dog die. So, don't start the waterworks yet.

Heart murmurs in dogs can be indicators of structural abnormalities in the heart or potentially heart disease. That's why it's crucial to have your vet perform a physical examination and the necessary diagnostic testing.

Are All Heart Murmurs The Same?

Like many other health conditions, heart murmurs in dogs can occur on a scale, and not all of them are the same - nor do they have the same effect on your pup's health.

The scale ranges from 1 (the faintest murmur) to 6 (the most severe murmur). To put it simply, this scale grades how loud heart murmurs sound.

We need to remember that this scale can only give us an idea of how severe the heart murmur is, but not if there's an underlying disease. That's why we need diagnostic testing to be sure.

Additionally, an essential characteristic of a heart murmur is the time of the heart cycle they occur in and if they are short or long. We also need to pay attention to where these murmurs appear the most and where they are the loudest.

While you're at home, pay attention to these things and tell them to your vet once you visit. It will help them identify the kind of heart murmur your dog might have. Your veterinarian must listen to what you've noticed since you - the person who spends the most time with your dog - play a considerable role in pointing the vet in the right direction. From there, diagnosing a disease should be easier.

Just like with most health issues, early detection is crucial in treating your dog's heart condition, so don't put off the vet visit.

Heart Murmur Configurations (Qualities)

There are four different heart murmur configurations:

  • Plateau murmurs (uniform loudness; associated with aortic valve insufficiency)
  • Decrescendo murmurs (start loud, then grow quieter)
  • Crescendo-decrescendo murmurs (they get louder and then quieter)
  • Machinery heart murmur (continuous heart murmur)

Innocent Heart Murmur

A dog getting checked out by a vet and a volunteer

Now that you know that heart murmurs can be graded on a scale - from faintest to most severe - I should also mention that there's an innocent murmur, also called a physiologic or functional heart murmur.

That should ease your mind a bit since this kind of physiologic heart murmur doesn't affect your dog's health. It's just an abnormal heart sound and nothing more.

Innocent heart murmur most commonly affects young puppies of large breeds while it's in the phase of rapid growth (6-8 weeks) and is usually outgrown by four or five months of age.

Innocent murmurs (physiologic heart murmurs) usually rate somewhere between 1 and 2 on the scale and have no effect on your dog's health, nor do they cause any clinical signs or symptoms.

Types Of Heart Murmurs

As I already mentioned, not all heart murmurs are the same; there are also several types. Here, I'll break down the most common ones:

  • Systolic murmur
  • Diastolic murmur
  • Continuous murmur

I'll also take a moment to discuss systolic murmurs since they're the most common out of the bunch.

Systolic Murmurs

Most heart murmurs have one thing in common - they occur during systole, which is a phase of the heart cycle in which the heart muscle contracts to pump blood out.

You may be wondering, what causes this?

The most common cause is pulmonic stenosis, which essentially means a narrowing of the blood vessel, leading to an obstruction of the blood flow.

Other potential causes include aortic valve insufficiency, heartworm disease, cardiomyopathy, hyperthyroidism, etc.

Dog Heart Disease: Underlying Diseases

A very small puppy being examined by a vet

Heart murmurs can have an underlying cause in the form of cardiac disease - but you know that.

Still, I want to highlight again that that's not always the case and that you should always consult with your vet before jumping to conclusions.

Here, I'll give you an overview of some of the most common underlying causes of heart murmurs.

Congenital Heart Disease In Dogs

Congenital heart defect or patent ductus arteriosus is a genetic disability that causes the heart vessel to function abnormally. This condition starts forming in utero and develops once the puppy is born.

Congenital heart diseases in dogs cannot be noticed at first. A young puppy affected by this cardiac disease won't seem any different than other puppies from the litter - other than maybe being a bit smaller.

It's important to get routine check-ups by a vet when the pups are still small so that turbulent blood flow can be detected and investigated further.

The good news is that there is treatment available, but unfortunately, not all young puppies respond to treatment the same. That means that it can either be managed and cured or can have a fatal outcome.

Some symptoms include shortness of breath - or difficulty breathing - inability to exercise, weakness, and stunted growth.

There are three types of congenital heart disease:

Aortic and pulmonic stenosis are some of the most common congenital diseases in dogs.

The way a vet can diagnose your pup with this condition is by doing some physical exams, blood tests, as well as doing chest X-rays.

A pug yawning

Mitral Valve Insufficiency

Mitral insufficiency happens due to high pressure created when the left ventricle contracts to pump blood out to the body. That causes the valve to wear out and become leaky over time. This condition is known as mitral valve insufficiency.

A leaky mitral valve can occur to dogs even as young as four years old.

Dilated Cardiomyopathy

Dilated cardiomyopathy is a structural heart disease present mostly in larger dog breeds. It causes progressive heart muscle dysfunction, chamber dilation, and eventually even congestive heart failure or death.

We still don't know the underlying cause for this condition, but we know that genetics definitely plays a role.

Unfortunately, there isn't an effective way to prevent your pet's heart from developing this issue, but treatments are available to help with the quality of life and maybe even lengthen your pet's life.

Signs Of Cardiac Disease Indicated By A Heart Murmur

A dog being monitored for its blood pressure

Prevention is better than cure. My point? It's best to pay attention to early dog heart disease symptoms accompanied by heart murmurs. That way, your vet can promptly diagnose your dog, and you can discuss further prognosis and treatment options together.

So, here are some common symptoms of heart problems in dogs and general signs of cardiac disease in dogs:

  • Decreased appetite
  • Exercise intolerance (even though there are no paw problems present)
  • Fainting/collapse
  • Difficulty breathing
  • Coughing
  • Arrhythmia in senior dogs

These symptoms can also be signs of heart failure in dogs - which requires you to react quickly.

Who Can Be Affected By Heart Murmurs And Cardiac Disease

I know that you'd be relieved if I told you that only certain types of dogs could have a heart murmur and be affected by cardiac disease. Sadly, I can't.

Many dogs can be affected - adult dogs, older dogs, small dogs; you get the idea.

But, as I said, you need to be aware of your dog's heart murmur. This way, you'll catch the underlying cause in time and be able to provide them with adequate treatment that can potentially prolong their life.

If you catch a heart murmur on time, there's a pretty good chance that they won't be affected by severe heart disease or experience dog heart failure symptoms. They may still develop less severe conditions, though.


So, we've discussed the most important facts about heart murmurs in dogs. I hopefully answered your questions - but now, let's reiterate all the crucial info here.

Most murmurs refer to abnormal heart sounds and by themselves aren't a problem. However, they could often indicate underlying causes and point to congenital heart defects - which is why you should react timely.

Heart murmurs have different types; they can be graded on a scale - based on how loud they are - and they have different qualities.

An innocent heart murmur can happen in puppies due to a growth spurt; they usually grow out of it before they turn one.

As far as types go, the most common type of heart murmur is a systolic murmur, which has a couple of causes. The most common one restricts blood flow by thickening the walls of the vessel and thus narrowing the passage. Restricted blood flow can then lead to further, more severe conditions.

A dog's heart murmur can point to some of the following cardiac diseases: leaky heart valve, dilated cardiomyopathy, congenital heart diseases, etc.

A heart murmur can be detected in your pet's heart regardless of the dog's breed, age, size, and so on.

With a heart murmur, your dog can show specific symptoms that can help your vet diagnose them easier. Try to look for other signs if you've noticed a slight heart murmur in dogs.

So, now that you know what a heart murmur entails, you can have some peace of mind and know that if your dog is otherwise healthy and exuberant, there's no need to worry. However, you should never replace a visit to the vet with reading online articles.

That means that if you notice anything that seems off about your dog's behavior, don't hesitate to talk to your vet.

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About the Author

A devoted pet parent to two lovely creatures – Charlie the Cat and Jimmy the Dog – a full-time assistant pet store manager, and an animal shelter volunteer. I've gathered knowledge about pets for almost a decade, and it all started in a small store called Jack's Pets.

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