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Dog Heart Murmur Life Expectancy Guide

One of the scariest things a vet can say is that they hear a heart murmur in your dog. It doesn’t matter if you are at a routine exam or there with a sick puppy. A heart murmur diagnosis is sure to cause your heart to skip a few beats. It is natural to be worried and wonder about the typical dog heart murmur life expectancy.

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The good news is that a heart murmur diagnosis does not necessarily mean that your dog is at any greater risk of dying! Scary as the diagnosis may be, dogs with heart murmurs often live long and healthy lives. In this post we are going to break down heart murmurs in dogs and explain how this diagnosis impacts your dog’s life expectancy.

Dog Heart Murmur Life Expectancy

Heart murmurs are a common diagnosis in veterinary medicine. While we tend to associate heart problems with older dogs, in fact many puppies and young dogs develop these murmurs as they grow. So what is a heart murmur and why do they happen?

What Is a Heart Murmur?

A heart murmur is simply an abnormal sound that is detected when your vet listens to your dog’s heart with a stethoscope. The abnormal sound is caused by turbulence in the blood being pumped through your dog’s heart.

A good way to understand a heart murmur is to picture a hose with a kink in the line. The hissing-sound of the water flowing past the kink is similar to a heart murmur.

So all a heart murmur diagnosis means is that there is some turbulence in your dog’s heart. In and of itself, a heart murmur diagnosis has no impact on the life expectancy of your dog.

The real question, and the one that matters in terms of life expectancy, is what is causing the turbulence?

How Is a Heart Murmur Diagnosed in a Dog?

Most of the time, a heart murmur is diagnosed at a routine vet visit. Many murmurs are so subtle that they can only be detected by listening to the heart with a stethoscope. Even then, low-grade murmurs can be easy to miss.

If your vet hears a heart murmur the first thing they will do is determine the grade of the heart murmur.

Heart murmurs are graded 1 through 6 based on how loud or intense they are. A level 1 murmur is a subtle sound, while a 6 is so loud you can actually feel the murmur with your bare hand.

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Grading Scale for Heart Murmurs in Dogs

Grade 1– barely audible.

Grade 2– soft, but easily heard with a stethoscope.

Grade 3 -intermediate loudness.

Grade 4– loud murmur that radiates widely, often including opposite side of chest

Grade 5– very loud, audible with stethoscope barely touching the chest; the vibration is also strong enough to be felt through the animal’s chest wall.

Grade 6– very loud, audible with stethoscope barely touching the chest; the vibration is also strong enough to be felt through the animal’s chest wall.

Once your vet has graded the murmur they will also classify it based on several other characteristics. They will consider the location of the murmur (right or left side of the heart) and whether the murmur is heard during the heart’s contraction or while it is relaxed (systolic vs diastolic).

Not All Heart Murmurs are Significant

Once your vet has finished their exam and looked over your dog’s history they will be able to walk you through their findings and recommendations. Your vet should have a pretty good idea of what is causing the murmur and whether you need to be worried.

You might be surprised to hear this, but in cases of low-grade heart murmurs your vet may just recommend keeping on eye on the situation. If your dog is otherwise healthy and has no other symptoms, you may not need to do further testing or see a specialist.

Innocent or Physiological Heart Murmurs

Some heart murmurs are completely benign. They indicate turbulence in the heart but they don’t have any impact on your dog’s overall health or life expectancy.

Heart murmurs in puppies are very common, for instance, especially in large-breed puppies. These so-called “innocent” murmurs usually appear around 6 weeks of age. Sometimes they come and go, and your vet may hear a murmur on one visit but not the next.

These murmurs are caused by changes in the heart as the puppy rapidly grows, but have no lasting impact on your dog’s health. Most of the time a puppy will outgrow the murmur. A puppy or young dog with an innocent heart murmur has the same life expectancy as a dog with no heart murmur.

Another common cause of low-grade innocent murmurs in dogs is stress. Sometimes a stressed dog may have a murmur while at the vet that is undetectable at home. In these cases, no treatment is needed and your dog should have a normal life expectancy.

Older dogs can develop these benign murmurs as they age too. My miniature schnauzer had a grade 2 heart murmur for the last 6 years of her life but never developed any signs of heart disease. As long as your dog is healthy and symptom-free you shouldn’t stress over a low-grade innocent murmur.

Structural Heart Murmurs

Many middle-aged dogs develop low-grade murmurs as they age. The valves in the heart can start to weaken and change shape, leading to the turbulence that causes the murmur. These murmurs are signs of structural problems in the heart itself.

There are 4 chambers in the heart, 2 on each side. When blood flows through the heart, it is pumped through the right atrium and ventricle and into the pulmonary artery. There it is diverted to the lungs where the blood is oxygenated. This blood returns to the left side of the heart, passing through the atrium and ventricle and then into the aorta where it heads to the rest of the body.

Inside each of those chambers are a series of flaps and valves that keep the blood moving in the correct direction. When these valves develop problems, either from age-related changes or infections, they may start to leak. A leaky mitral valve is a common cause of a heart murmur, for instance.

Structural problems in the heart include leaking valves, thickening or narrowing of valves or blood vessels or thickening of the heart muscle itself. These changes can be minor or major, and are often but not always progressive.

A heart murmur diagnosis in an older dog may or may not affect their life expectancy.

It depends on what is causing the murmur. Many vets do not treat an acquired heart murmur as long as the dog isn’t showing any symptoms of heart disease.

Congenital Heart Murmurs

Not all murmurs in puppies are innocent murmurs. If your puppy has an intense murmur or one that does not improve as they grow your vet may start to suspect they have a congenital heart defect.

Congenital heart defects are structural defects in the heart that your dog is born with. They may be mild or severe, and are fairly common in some breeds of small dogs.

Some congenital heart defects are surgically-repairable but many are not. Unfortunately, congenital defects may dramatically reduce the life expectancy of your dog if they can’t be corrected through surgery.

If your dog has a congenital heart defect, it is important to get an early diagnosis and have a cardiologist involved. While medications can often reduce the impact of a congenital heart defect, without surgery most dog with a defect like this will go into heart failure at a young age.

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When Is a Murmur a Problem?

So when do you need to be worried about a heart murmur?

Generally, if your dog has a low-grade murmur ( grade 1 or 2) and has no other symptoms of heart disease your vet may recommend a wait-and-watch approach. They may have you come in more frequently for exams, or have you monitor your dog’s breathing at home.

Heart murmurs can be a serious sign of other medical problems, however. If your dog is sick or showing signs of heart disease then your vet will likely want you to consult with a specialist.

Should You See a Specialist?

Honestly, having a dog with a heart murmur evaluated by a cardiologist is never a bad idea if you can afford the expense. Many cardiologists are covered under pet insurance plans too.

A cardiologist will be able to view your dog’s heart using a special kind of ultrasound called an echocardiogram. This will allow them to view the chambers, valves and arteries and check the thickness of the heart wall.

You will get a specific diagnosis and treatment plan from your cardiologist and you will have the benefit of knowing exactly what your dog faces. The only true way to know how a heart murmur will impact your dog’s life expectancy is to seek specialty care.

When my schnauzer first developed her heart murmur I was so worried I had trouble sleeping. Taking her to a cardiologist and getting confirmation that her murmur was insignificant brought me a lot of peace of mind.

The most important thing to do if your dog has a heart murmur is to be aware of the signs of cardiac distress. A dog can have a heart murmur for years before they develop signs of heart disease. If you know what to watch for, you can get your dog into a vet before they go into a crisis.

Symptoms of Heart Disease

If your dog starts to display any of the following symptoms, have them evaluated by a vet as soon as possible. Don’t put it off, and go to an emergency vet if your dog is having problems breathing or has collapsed.

For dogs with existing murmurs, these symptoms can be a sign that the heart is starting to have problems functioning. If left untreated, dog with these symptoms may go into congestive heart failure (CHF).

CHF is the end-stage of heart disease. Once your dog’s heart begins to fail, your treatment options become more limited and focused on quality-of-life care.

Signs that your dog’s heart is starting to struggle include:

  • Coughing

  • Difficult or rapid breathing

  • Congestion or “noisy” breathing

  • Exercise intolerance (reluctance to exercise)

  • Weakness or lethargy (tiredness)

  • Fainting episodes

  • Gray or blue gums

  • Abdominal distention (a pot-bellied appearance)

  • Collapse

Heart Murmurs Are Hard to Predict

As you can see, heart murmurs are difficult to predict. The life expectancy of a dog with a murmur will vary a lot and will depend on what is causing the murmur. Many dogs have murmurs for years and never develop any signs of heart disease, while others slip into CHF rapidly.

Some breeds are more prone to developing heart disease. King Charles Cavalier Spaniels, Doberman Pinschers, Pugs, Chihuahuas and Boxers are all breeds commonly seen at cardiology offices.

The good news is that many dogs with murmurs never develop active heart disease, and even those that do often do well with treatment. I have seen dogs survive with CHF for several years with diligent care and medication.

A heart murmur is not necessarily a dangerous diagnosis, even though it sounds scary. There are also many great treatment options for dogs with early-stage heart disease. When in doubt, talk to your vet or seek out a cardiologist for advice.

Thank you for reading this post on heart murmur’s in dogs! If you found it useful and informative, please take a second to share and post on social media. If you have any comments or questions, please contact me directly at [email protected], or leave a message in the comment box below. I always get back to my readers.

Author’s Bio

Jen Clifford has a B.A. in Biology from Reed College. She was a field biologist for several years, and then spent 10 years working in veterinary medicine as a receptionist and technician.  Jen is currently a freelance writer living in the Pacific Northwest with her Tribe of pets. She is a passionate animal lover who is dedicated to helping people find solutions to their pet-related challenges.

You can find more of her work at her website