Heart Murmur in Dogs: Causes, Treatment & Prognosis

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Last Updated on March 5, 2024 by Aftab Tariq

Heart murmur in dogs is an important aspect of their health, much like it is for humans. When your vet listens to your dog’s heartbeat using a stethoscope, they’re paying attention to something called a heart murmur.

But what exactly does it mean if your dog has a murmur, and what steps should you take if your vet detects one?

What is a Heart Murmur?

A heart murmur is a strange sound coming from the heart, which a doctor can hear by using a stethoscope.

What Causes a Heart Murmur?

Heart murmur in dogs causes can be classified into two types: “innocent” or “physiologic,” and “pathologic.” Innocent or physiologic murmurs are typically harmless and not indicative of any disease.

However, “pathologic” murmurs may indicate a problem either within the heart itself, such as a heart disease, or elsewhere in the body, unrelated to heart disease.

Do all Murmurs Have a Similar Sound?

The classification of heart murmur in dogs stages, ranging from Grade I to Grade VI, is based on their loudness, reflecting the level of turbulence within the heart.

A Grade I murmur is very soft and might only be heard sometimes and in one place on the chest. A Grade VI murmur is very loud and can be felt when you put your hand on the chest where the heart is.

Murmurs also depend on when they happen during the heart cycle and how long they last. Most dog murmurs happen during systole, when the heart squeezes to push blood out.

Your vet will assess the unique features of the murmur and any signs of heart murmur in dogs symptoms your pet may exhibit to diagnose the underlying cause.

Which Structural Heart Issues Result in a Heart Murmur?

The heart is like a house with four rooms: the left atrium, left ventricle, right atrium, and right ventricle. Blood moves from the right side of the heart to the lungs through a big blood vessel called the pulmonary artery to get oxygen, turning it into oxygenated blood.

Then it goes to the left side of the heart and out to the body through a big blood vessel called the aorta. Each room in the heart has a door called a valve. These valves stop oxygenated blood from going backward as the heart pumps.

When a dog has a heart murmur, it means there’s something wrong with the heart’s structure. This could be a problem with a valve that’s not closing properly, a valve or blood vessel that’s too thick or narrow, or an unusual hole between heart chambers or blood vessels. This trouble in the heart creates turbulence, or swirling, of the blood.

Heart murmurs in dogs can be caused by structural heart problems that happen either when the dog is born or later in life. Some dogs are born with congenital heart diseases, meaning their hearts are defective from birth.

Certain breeds are more likely to inherit these conditions, such as subaortic stenosis, pulmonic stenosis, and patent ductus arteriosus. But not all heart problems are inherited. Some, like ventricular septal defects, atrial septal defects, and Tetralogy of Fallot, can occur without a clear genetic cause.

The most common reason for a heart murmur in older dogs is a condition called mitral insufficiency, also known as mitral regurgitation. This happens when the mitral valve, one of the heart’s valves, becomes thickened and starts leaking.

This issue is more common in smaller dog breeds. Other reasons for a heart murmur in older dogs include bacterial endocarditis, caused by an infection that affects a heart valve, and dilated cardiomyopathy (DCM).

“Heart problems can be present from birth (congenital) or develop later in life (acquired).”

Which Non-Heart-Related Issues Lead to a Heart Murmur?

Some things outside of the heart can also cause what’s called a “functional heart murmur.” This type of murmur might happen because of certain health problems like anemia (which means there aren’t enough red blood cells), low protein levels in the blood, a fever or infection, being pregnant, being overweight, or being very skinny.

When a dog has anemia or low protein levels, their blood becomes too thin or watery. This makes the blood flow through the heart valves more turbulent, potentially resulting in heart murmurs at different heart murmur in dogs levels.

In young puppies, anemia or low protein levels can happen because of a serious parasite problem, like intestinal worms, blood parasites, fleas, or ticks. Adult dogs might become anemic because of blood loss or they might have another serious health issue.

What Constitutes an Innocent or Physiological Heart Murmur?

An innocent or physiologic heart murmur is a heart murmur that doesn’t affect the dog’s health. It’s quite common for young puppies, especially big ones, to have this type of murmur while they’re growing quickly.

The murmur might show up when they’re about 6-8 weeks old, and most puppies with this kind of murmur will grow out of it by the time they’re about 4-5 months old.

This type of murmur isn’t harmful. Usually, a physiologic or innocent heart murmur is soft (usually Grade I-II out of VI) and doesn’t cause any symptoms or problems.

How is a Heart Murmur Detected?

In many instances, a heart murmur is discovered during a veterinary examination when your veterinarian listens to your dog’s heart using a stethoscope.

How Can we Determine if a Murmur Indicates a Significant issue?

If your vet finds a heart murmur in your dog, they’ll ask you some questions about your dog’s health. They’ll also check your dog’s overall physical condition to see if there are any signs that suggest more tests are needed.

If your puppy still has a faint heart murmur, your vet might suggest checking again in a few weeks to see if it’s gone or lessened. This could mean it’s just a harmless murmur.

Similarly, if your grown-up dog is really stressed during a check-up and has a faint murmur, your vet might want to re-check when the dog is calmer. Sometimes, if a dog is super excited or panting a lot, it’s hard to know if the strange sounds are from a heart murmur or just from being worked up.

A dog with a heart murmur from a heart problem or something else will usually show some symptoms. These can include not eating well, losing weight (or not growing right if they’re a puppy), having trouble breathing (especially at night or after resting), getting tired easily during exercise, fainting, having pale gums, or coughing.

If your vet notices an odd rhythm to the heartbeat or weak pulses, it’s more likely there’s a problem causing the murmur. If they think the murmur is from a heart problem or something outside the heart, they’ll recommend more tests.

In most cases, these tests should happen right away so treatment can start as soon as possible.

“Identifying abnormal sounds in an overly excited or panting dog can be tricky, as it’s hard to tell if they’re from a heart murmur or just increased heart rate and heavy breathing.”

What other Tests May be Recommended?

Your vet might suggest X-rays, an electrocardiogram (ECG), or an ultrasound of the heart (echocardiogram) based on your dog’s symptoms. If they think the heart murmur might be due to another illness, they may also recommend blood tests or other checks.

An echocardiogram, especially one with a Doppler exam, is the best way to find out where a heart murmur is coming from. It shows the heart’s size and how it moves.

The Doppler exam, a special type of echocardiogram, can measure how fast and in which direction blood flows across the heart valves and in the heart chambers. This test often helps to pinpoint where the problem is causing the murmur.

What are the Treatment Options for a Heart Murmur?

Treatment for heart murmur in dogs depends on what’s causing it. If it’s just a harmless murmur, called a physiologic heart murmur, no treatment is needed, but it’s good to keep an eye on it.

If there’s another problem causing the murmur, like a heart defect, treatment will depend on what the vet finds. It might include adjusting the heart murmur in dogs diet, medication, or extra care.

Some heart defects, like pulmonic stenosis or patent ductus arteriosus, can be fixed with surgery. Your vet will tell you what’s best for your dog and what you can do to help them feel better.

What is the Prognosis?

The outlook for dogs with a heart murmur varies a lot, depending on what’s causing it. If it’s just a harmless murmur, called physiologic, no treatment is needed and the dog usually does well.

But if the murmur is from another problem that can be treated, like an illness, it might go away with time.

For dogs born with a heart problem, the prognosis is different for each dog, depending on what type of defect they have. If surgery can fix the problem, the prognosis is good.

When observing symptoms of heart murmur in dogs, such as those indicative of dilated cardiomyopathy, the prognosis hinges on the severity of these indications. While some dogs respond well to long-term medication, others may face a less favorable outlook.

The prognosis for dogs with bacterial endocarditis, an infection in the heart, depends on how bad the infection is and which valve it affects. Good dental care is important to prevent this kind of infection.

Every dog is different, so your vet will talk to you about what’s best for your dog. They’ll keep an eye on your dog’s condition and might need to do more tests from time to time to see how they’re doing.

Remember, taking care of your dog’s teeth is crucial to prevent issues like bacterial endocarditis.

“The forecast varies from very good to very serious, depending on the reason behind the murmur.”

Note: When it comes to grade 3 heart murmur in dogs life expectancy, it depends on various factors like underlying health issues and prompt medical care.
Understanding the significance of a heart murmur in dogs Veterinary Partner provides valuable insights into diagnosis and treatment.

Frequently Asked Question

What are the Implications of a Heart Murmur in Dogs Grade 4?

Grade 4 murmurs are loud and can be heard on both sides of the chest, signaling a more serious heart issue. At this point, it’s important to do more tests and possibly take action.

What are the Characteristics of a Stage 3 Heart Murmur in Dogs?

A stage 3 heart murmur in dogs is moderately loud and typically audible over a wider area on the chest. It may indicate a moderate underlying heart condition, prompting the need for further evaluation by a veterinarian.

What does the Classification Heart Murmur in Dogs Grade 2 Signify?

A Grade 2 heart murmur in dogs is relatively soft and may only be heard in a specific area of the chest. While it may not necessarily indicate a serious underlying heart issue, it’s essential for a veterinarian to assess and monitor the dog’s condition to ensure optimal health.

What Does the Heart Murmur in Dogs Rating Scale Indicate?

Heart murmurs are graded on a scale from 1 to 6, with 1 being the softest and 6 the loudest. Vets use this scale to figure out what’s causing the murmur and what to do next.


Heart Murmurs in Puppies

American Kennel Club

Veterinary Medicine &Biomedical Science

Animal Medical Centre


Aftab Tariq

I am a dedicated content writer with more than five years of experience, particularly skilled in the art of storytelling. My writing journey commenced during my college years, where I pursued journalism and unearthed my talent for creating captivating narratives.

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