Heart Murmur in Dogs: Causes, Symptoms, Treatment & More

Heart Murmur in Dogs: Causes, Symptoms, Treatment & More

Last Updated on February, 2023

Heart murmurs are often seen among dogs, a common problem that all dog parents go through. This condition can occur irrespective of your dog’s breed, sex, age, or health conditions. This could be due to many reasons, which we will understand in the latter part of this article. So keep reading! 

Quick Summary

A heart murmur is an unusual sound or vibration from the heart, caused by an unsettled blood flow.

There are three main types of heart murmur – diastolic, systolic and continuous – each with their own symptoms.

Heart murmur can be caused by a heart structure abnormality, such as a leaky heart valve, or by an extracardiac condition, such as anemia.

What is a Heart Murmur?

veterinarian checking a dog's heartbeat

A heart murmur is an unusual sound or vibration from the heart. It also means that there is an unsettled blood flow in the heart. A heart murmur will sound like a whoosh, and I am not going to lie; it is quite alarming to have a heart murmur in your dog’s heart. Our blood flow is meant to flow in one direction—a disturbance in the middle of the pathway where the blood flows create heart murmurs or a sound. 

It is also essential to understand that there could be heart murmurs in dogs that are not as dangerous as it sounds like innocent heart murmur. Which we will talk about more in detail in this article. 

A heart murmur is detected by carefully inspecting it through the help of a stethoscope. When the veterans identify heart murmurs in dogs, they will do further checkups to find the cause for this. 

Usually, it is either because of a structural defect or extracardiac conditions. Congenital heart defects cause most structural heart disease—congenital, meaning born with heart defects. Extracardiac diseases are caused by an issue in the heart’s electrical system. 

Types of Heart Murmurs

Also, there are three main heart murmur types: Diastolic, Systolic and Continuous. 

Diastolic Heart Murmur

Diastolic heart murmurs occur when the heart is filled with blood. Aortic insufficiency is caused by narrowing the aortic and pulmonic valve, which causes a diastolic heart murmur. 

Systolic Heart Murmur

Systolic murmurs occur when the heart is emptying with blood. This heart murmur occurs due to mitral valve or tricuspid valve regurgitation. 

Continuous Heart Murmur

Continuous Murmurs is when there is a murmur in the dog’s heart throughout. Continuous heart murmur occurs during both contraction and relaxation of the heart. 

Configuration of Heart Murmurs

A dog lying on the bed

Do all heart murmurs sound the same? The answer is no! Depending on the configuration of the heart murmur, the sound differs. 

  • Plateau murmurs are generally uniform in sound and often caused by blood regurgitation through an abnormal valvular orifice. Regurgitation is when the valve does not function properly and causes blood backflows.
  • Crescendo-decrescendo murmurs are caused by turbulent blood flow flowing forward. In simpler terms, when there is a disturbance to the blood that flows forward. These murmurs start louder and then get softer. This murmur is similar to aortic and pulmonic stenosis. 
  • Decrescendo murmurs are similar to diastolic heart murmurs, which start louder and get softer.

Heart Murmur Grades in Heart Disease 

There are six grades of heart murmurs in dogs. Heart murmur grade grades the heart murmur depending on how loud the murmur is. 

Grade I – Barely audible. 

Grade II – Soft but can be heard through the stethoscope. 

Grade III– Related to mechanics of blood circulation and loud. 

Grade IV – Radiate loud and wide it even vibrates the opposite side of the chest. 

Grade V – A bare touch on the heart with the stethoscope is sufficient to hear the murmur. Very loud. It can even be heard by keeping the ear to the animal’s chest wall. 

Grade VI – The vibration is so strong that it can be heard/ felt by just touching the animal’s chest walls. 

What is an Innocent Heart Murmur? 

A veterinarian checking a puppy's heartbeat

An innocent murmur is harmless and can be seen in small puppies. These grade III or lesser murmurs usually do not require any medication. The heart resolves the murmur by itself with time.

An innocent murmur occurs when there is a turbulent, but safe to say that the heart can manage it out and need no medical intervention. So if your vet diagnoses an innocent heart murmur in your dog, do not worry! (1)

Symptoms of Heart Murmurs in Dogs

Now, this is a very common question, how to know if my dog has abnormal heart sounds or a cardiac disease? Look I have got you covered, below mentioned are a few of the symptoms that can be seen commonly among dogs with heart murmurs. 

Persistent Cough, Excessive Panting 

When the heart swells, pressure is created in the area of the lungs. As a result, your dog might cough more than usual, which means blood flow disturbances. 

Exercise Intolerance, Lethargy, or Weakness

This is another common symptom of congenital heart disease.

When the heart cannot function optimally, your dog cannot do everyday activities. Instead, he will feel more tired and weak at all times.

Abnormal Breathing or Excessive Panting

Persistent cough and excessive panting are mostly coupled together. This abnormal breathing is prevalent during the nighttime while sleeping or when they stand up from laying down. 

Pale Gums 

Pale gums are a common symptom of heart murmur in dogs. This is also a serious sign of a cardiac disease restricting the heart from functioning properly. While this could also be due to dental disease, there is no harm in taking your dog to the vet for immediate medical care. 

Distended Abdomen

This is referred to as ascites. Blood fluids collected in the abdomen are the leading cause of this condition. The tummy of your dog will be bloated more than usual. It can be a threat to your dog’s health.

Episodes of Collapse 

This is a reason to get medical treatment because abnormal collapse episodes could be for any reason. When it comes to dogs’ heart-related conditions, there is a shortage of blood flow to the brain. As a result, the dog becomes unconscious and collapses. 

What Causes a Heart Murmur in Dogs?

A dog lying on the wooden floor

As I have previously stated in the article, the cause of a dog’s heart murmur can differ, whether it is a heart structure abnormality or an extracardiac condition. 

Heart Structure Abnormalities 

Heart structure abnormalities are associated with problems in heart valves like leaky heart valves or a hole in a heart muscle. These abnormalities are mostly birth defects, but in some instances, dogs can develop these with time too. The most common heart structure abnormalities are; 

  • Degenerative mitral valve disease – A leaky mitral valve causes this condition. The abnormality causes the blood to flow back to the upper right chamber, causing tricuspid heart failure. 
  • Tricuspid valve stenosis – This is a narrowing of the tricuspid valve opening. 
  • A ventricular septal defect is when the wall separating the heart’s lower chambers does not fully develop. 
  • Dilated Cardiomyopathy – The heart cannot pump blood efficiently because the pet’s heart muscles are too weak and enlarged. As a result, it causes a disease called dilated cardiomyopathy.
  • Patent ductus arteriosus – This is when two major blood vessels leading blood from the heart fail to close after birth. 

Extracardiac Condition

Certain other conditions that are not within the heart’s control and not related to the heart could cause heart murmurs in dogs. Few of these are, 

  • Anemia 
  • Heartworm disease 
  • Hyperthyroidism 
  • Hypoproteinemia 
  • Infections

Prognosis for Heart Murmurs

Particular heart murmurs like an innocent heart, or physiologic heart murmurs will resolve by the heart itself. So it does not require any intervention. But other types, such as dilated cardiomyopathy, can be very serious and sometimes deadly. 

Prognosis and treatment options for congenital heart disease are different because some defects can be corrected through surgeries. However, other types can also be treated and cured to a certain extent through medications for long periods. 

The exact prognosis of your dog will depend on the cause of its heart murmur and several other external factors, which will be communicated to you with detailed explanations. 

Treatments for Dog Heart Murmurs 

a dog lying on a table, and a veterinarian holding a test report

Treatments for dog heart murmurs vary from the clinical signs it shows. Continuous murmur can result in doing multiple tests such as blood tests, scans and other medical tests. 

Treatment for physiologic heart murmur is different to that of the treatment for an innocent heart murmur. For innocent murmurs of 1-2 grades require constant exercise and maintaining a healthy weight. 

For louder murmurs vets often prescribe angiotensin-converting enzyme inhibitors, diuretics, and positive inotropes which support and control the underlying cause. These will bring the heart cycle back to normal in most instances. 

If the dog’s heart is enlarged and does not show any congenital heart diseases it is likely that a pimobendan (TM Vetmedin) will be prescribed. However diagnosis of this condition is tad hard. 

Treatment for subsequent leaky mitral valve, heart valve replacement,aortic valve replacement, leaky heart valve correction or other types of complex surgeries require constant professional care for prolonged periods depending on the severity of the condition. 

Recovery After Heart Murmur Correction Surgeries or Treatments

Post congestive heart failure or after taking treatment for a dog’s heart murmur, the recovery plays a major role. The abnormal heart sound tends to return back if proper care is not taken. Other than innocent murmurs every other type of congenital heart disease is a threat to your dog’s life, yes I said it right, even after treatments it could still be a big threat. 

However, make sure to restrain your dog’s activity levels as much as you can. Especially with young puppies and even adult dogs. Monitor the dog’s blood pressure at all times. 

Follow up and make sure to provide adequate medications prescribed by your vet if the diagnosis was a functional heart murmur due to anemia. 

Recovery for dilated cardiomyopathy varies if a surgery was performed.

If so, it is important to monitor the sutures and avoid your dog from licking the wound. Because an infected dog wound is the last thing you want to take care of at this moment!

How to Prevent Heart Murmurs and Cardiac Disease in Dogs? 

Murmurs and Cardiac Disease Preventing ways

This is a very practical question that all pet parents want answers to! Here are a few essential tips for you to follow to prevent heart murmurs and keep your dog’s heart healthy! Also, it is essential to understand that not all heart murmurs can be prevented. But there is a chance if the problem is detected in young puppies at early stages. 

Regular Dental Cleaning 

Dental cleaning helps a lot in preventing heart problems. Regular dental cleaning and brushing teeth daily are highly recommended. It is also good to give dental chews now and then because they help prevent heart murmur in dogs. 

Diet and Nutrition 

This applies to us too. Proper diet and nutrition can prevent any underlying cause, chronic valve disease leading to abnormal heart sounds. Feed your dog with high-end supplements and make sure that all the necessary nutrition is given to the dog!


Daily exercises can help to avoid any type of severe heart issues. However, this has to be done every day or regularly. 


Heart murmurs are not something that you can do trial and error with. So the best is to seek medical advice as soon as you see symptoms. But I must remind you that prevention is better than cure, so incorporating healthy food that helps your dog’s heart is a smart move. Food items such as garlic, CBD oil, omega 3 fatty acids, hawthorn berries and dandelion leave some of it. 

The loudness of a heart murmur depends on the underlying condition. However if it is an innocent murmur of the heart, you will not hear without a stethoscope. Generally a heart murmur within the scale of 4-6 can be barely heard by placing the ear near the heart. 

Generally the vet will prescribe the type of test to be done depending on each circumstance. Chest X-rays, echocardiograms or blood tests are quite popular. 

Wrapping Up

Finally, I will conclude this article by giving you one important piece of advice. Heart is an essential part of our bodies and the same applies to dogs. The difference is we can talk and dogs cannot. There are plenty of chances that you might miss out on diagnosing a heart murmur leading it to unpleasant circumstances. In order to avoid such bad situations, take your pet’s health seriously. Do check ups when necessary. 

If you detect any unusual behavior, any symptoms of heart failure or murmurs immediately take to healthcare professionals and identify the underlying cause. The clock is ticking and time is precious! Take care of your furry friend because they deserve love, care and affection. 

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Thomas Villalpando is the main author of IPet Guides. He spends his time reading, training, and working with several Dogs' behaviors. You can find more about him here.

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