It’s scary when your dog gets a diagnosis of a heart murmur. You want to know what it means, how it’s treated, and what kind of life expectancy you can expect for your dog.
This dog heart murmur life expectancy guide is designed to give you hope and a better understanding of the diagnosis.
Rest assured, dogs with heart murmurs often live long and healthy lives.
Once a diagnosis is made, it’s important to understand that your dog’s life expectancy isn’t necessarily related to the heart murmur.
Heart murmurs are a common diagnosis in veterinary medicine
While we tend to associate heart problems with older dogs, puppies and young dogs can develop these murmurs as they grow.
What Is a Heart Murmur?
A heart murmur is an abnormal sound 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. At this stage, the veterinarian will want to determine what is causing the heart murmur.
TIP: 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.
Top 7 Symptoms That May Determine Heart Murmur Life Expectancy in Dogs
If your dog starts to display any of the following symptoms, have them evaluated by a vet as soon as possible.
The cause of coughing in dogs can range from an infection (viral, bacterial, or fungal) to heart disease. Heartworms, Parvo virus (flu) and Kennel Cough can all cause a dog to cough.
Sound and severity of cough is not directly related to a dog heart murmur or life expectancy. The issue to consider is the severity of the underlying disease.
Only a licensed veterinarian can diagnose the reason for your dog’s cough.
It’s normal for a dog to cough sometimes, but if you notice more of a recurrence, make an appointment for your dog.
Dog Has Difficulty Breathing (Dyspnea)
Rapid breathing isn’t the same as panting on a hot day or after exertion. When a dog is having trouble breathing, you’ll notice other problems like anxiety and an unusual stance.
Your dog might sit or stand with legs wide. The dog’s mouth may remain open as he tries to get more air into his lungs.
Difficulty breathing is one sign of heart disease in dogs and should be checked if it is a consistent, random event that doesn’t directly relate to a quick bout of exercise, etc.
Congestion or “Noisy” Breathing
Brachycephalic dogs (dogs with flat faces and very short noses) are known for noisy breathing. You might heart “snorting”, “snoring sounds”, or a high-pitched sound known as stridor.
You know what sounds normal for your dog and what doesn’t.
If you suspect any kind of unusual breathing patterns, it’s time to take your dog to the veterinarian for an assessment. It could be a sign of heart disease in dogs.
Recognizing an exercise intolerance in dogs can be tricky.
It’s easy to blame old age, a shift in weather, sore joints, or any number of things on a dog’s reluctance to exercise.
Most dogs, however, are happy to get out for a regular walk. If your dog is showing signs of distress and suddenly refuses to move, he/she could be showing signs of a heart murmur.
Weakness or Fatigue
The heart muscle moves vital oxygen through the body to all of the organs. Without enough oxygen, the vital organs become starved.
If your dog’s heart is working too hard (high heart rate) or not hard enough (heart failure) he/she is going to be exhausted.
Fainting in dogs (syncope) occurs when a sudden shift in heart rhythm (could be very fast or very slow) halts adequate blood flow to the brain.
Fainting on it’s own isn’t particularly dangerous. However, the underlying cause could be.
Gray or Blue Gums
Gray or blue gums are caused by lack of oxygenated blood flow through the body.
If your dog’s heart is not properly pumping blood, he/she may have gray or blue-tinged gums. Sometimes, discolored gums are a sign of dehydration unrelated to heart conditions.
Abdominal Distention (Pot Belly)
The sudden appearance of a pot-belly on a dog coud be related to heart disease.
When the heart cannot pump blood adequately through the body, fluid build-up can occur in the tummy.
In severe causes of heart disease, the body simply cannot generate enough energy.
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).
This is a great video that goes into more details about heart murmurs in dogs. Watch!
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?
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.
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.
Heart Murmur Qualities
There are four qualities of heart murmurs known as: plateau, crescendo-decrescendo, decrescendo, and machinery.
Does your dog have any of these? Here are the definitions:
These are characterized by a steady loudness. They are usually associated with an aortic valve insufficiency.
These murmurs get louder and then quieter. Conditions such as aortic and pulmonic stenosis may be the cause.
These murmurs start loud and then get quiet. They are usually seen with either an aortic valve insufficiency or a ventricular septal defect.
Machinery quality, or continuous murmurs, are associated with congenital heart defects in dogs.
What Causes Heart Murmurs in Dogs?
Causes of heart murmurs are generally due to blood flow disturbances.
These can be:
- Abnormal valves or vibrations
- Obstruction, diseased valves, or dilated vessels
- Disturbances caused by regurgitant flow
In some cases, underlying disease may be the cause.
Systolic Murmurs in Dogs – Potential Causes
The most common cause of systolic murmurs is due to a narrowing of the blood vessel that causes obstruction of the blood flow.
Other underlying conditions that could cause a systolic murmur include:
- Heartworm disease
- Aortic valve insufficiency
- Mitral and tricuspid heart failure
- Systolic anterior mitral motion
Diastolic Murmurs in Dogs – Potential Causes
This type of murmur is very rare in dogs. When it happens, however, it is usually associated with aortic insufficiency. Aortic insufficiency occurs when the aortic valve does not close tightly.
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.
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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 https://MyWickedTribe.com.