Heart Murmurs in Dogs: What You Need To Know

7 min read
7 min read

Updated - Jul 22nd, 2022

Much like humans, dogs can develop heart murmurs. A heart murmur refers to an abnormal noise within a dog’s regular heartbeat, caused by turbulent blood flow. There are three types of heart murmurs that can occur in dogs: 

  • Systolic murmur. This is the most common type of heart murmur in dogs. A systolic murmur occurs during the phase in which the heart pumps blood out as it contracts. This phase is called systole.
  • Diastolic murmur. This is the least common type of heart murmur in dogs. A diastolic murmur occurs during diastole, the period when the heart rests between beats. It is usually caused by a leaky aortic valve.
  • Continuous murmur. A continuous murmur can be heard during both systole and diastole. It most commonly occurs as a result of patent ductus arteriosus (PDA), a condition in which the opening between two major heart vessels which usually closes shortly after birth remains open.

A heart murmur can be caused by a wide variety of conditions, which makes care quite different for each dog. Treatment depends on the cause and severity of the heart murmur. To determine the correct course of action, a vet will diagnose a heart murmur, classify it, and then perform tests to determine its cause.

Symptoms of heart murmurs in dogs

Heart murmurs in dogs are not conditions within themselves — rather, they are symptoms of other health conditions, many of which are treatable.

Your dog’s heart pumps oxygen-rich blood throughout their body. As blood flows through the heart and is pushed out again, you can hear the rhythmic sound of your pup’s heartbeat, usually in a regular “lub dub“ pattern. A heart murmur is an abnormal noise within your dog’s heartbeat. It results from a disturbance in the pattern of blood flow. 

A heart murmur is sometimes accompanied by the following symptoms, which are also caused by other conditions: 

  • Increased and/or irregular heartbeat
  • Exercise intolerance
  • Fatigue
  • Hacking cough
  • Excessive panting
  • Fainting
  • Excessive water retention
  • Lack of appetite
  • Discolored (blueish) gums and/or tongue   

Causes of heart murmurs in dogs

Heart murmurs are most often caused by structural issues within the heart. Some dogs are born with heart valve or blood vessel abnormalities that cause turbulence in blood flow. These from-birth abnormalities are called congenital heart defects. Other dogs develop heart problems later, as a result of other health conditions. 

Some common causes of heart murmurs in dogs include:

  • Anemia. This is a condition in which your dog’s body doesn’t produce enough red blood cells.
  • Heart disease (cardiac disease). This includes congenital heart disease, and heart disease developed later in life.
  • Aortic insufficiency. This is a condition in which the aortic valve does not properly close, causing blood to flow back out of the heart. 
  • Mitral valve disease. This is a condition in which the valve between the left atrium and left ventricle of the heart does not properly close.
  • Dilated cardiomyopathy. This is a type of heart muscle disease that causes the ventricles to thin and stretch larger.
  • Patent ductus arteriosus (PDA). This is a condition developed by some young puppies in which the opening between two major heart vessels which usually closes shortly after birth remains open.
  • Pulmonic stenosis. This is a condition in which the pulmonary valve narrows.
  • Endocarditis. This is an infection of the heart’s inner lining.
  • Subaortic stenosis. This is a narrowing of the area below the aortic valve, causing blood flow obstruction. 
  • A ventricular septal defect. This is a congenital condition in which there is a hole in the wall between the two ventricles.


A vet will diagnose a heart murmur by listening to your dog’s heart with a stethoscope.

The vet will classify the murmur according to its location and loudness. They’ll determine if the murmur is systolic, diastolic, or continuous. The vet will also grade the murmur’s loudness on a scale of I to VI, VI being the loudest. The murmur’s volume is often indicative of its severity, and also can help a vet determine its cause.

Once a vet has diagnosed and determined the type of murmur, they will perform any number of diagnostic tests to determine its underlying cause. These tests can include:

  • Urine and/or blood tests
  • Chest x-rays 
  • Echocardiogram 
  • Electrocardiogram 
  • Ultrasound of the heart


Since a heart murmur can be caused by many different conditions, treatment options vary widely. Once a vet has determined the cause of the murmur, they can devise a plan for treatment for your dog’s condition. Sometimes, a general practitioner will refer you to a veterinary cardiologist.

Not all heart murmurs require treatment. A vet may diagnose your dog with an innocent heart murmur (sometimes called a physiologic murmur). This means the murmur does not pose any risk to the dog’s health. Innocent murmurs are most common in young puppies. Puppies tend to outgrow these murmurs by the time they reach five months of age.

Recovery and care

Once your dog is diagnosed with a murmur, you should monitor it carefully. Make sure to regularly check in with your vet, and report any new symptoms your dog may experience.


A heart murmur is not a preventable condition — especially given the fact that many of the heart conditions that cause murmurs are congenital. Heart murmurs that are detected early are more likely to be successfully treated and managed than those detected after they’ve been present for a while, so make sure to prioritize regular vet visits. 

Generally, promoting a healthy lifestyle for your dog may cut down on their risk of developing heart conditions.

What to expect at the vet’s office

First, a vet will use a stethoscope to listen to your dog’s heart. If the vet hears any abnormal sounds, they will diagnose your dog’s heart murmur, and classify it according to location and volume. 

The vet will then perform a series of diagnostic tests to determine the cause of the murmur. These tests may include chest x-rays, an echocardiogram, an electrocardiogram, and/or an ultrasound. Be sure to report any symptoms or unusual behaviors your dog has been experiencing, as this also may be useful information in determining the cause.

The bottom line

A vet can diagnose a heart murmur and determine the cause. Since each heart murmur’s cause and severity is different, a vet will determine the course of action that’s right for you and your pup.


Can pet insurance cover accidents and illnesses with heart murmur symptoms?

Pet insurance plans, like Pumpkin pet insurance plans, are designed to help you tackle unexpected accidents or illnesses. If your pet is unexpectedly diagnosed with an illness or accident with heart murmur symptoms, Pumpkin plans can help cover eligible diagnostic testing needed to determine the cause. They may also cover treatment for a number of unexpected accidents and illnesses with heart murmur symptoms.

Are certain dog breeds more susceptible to heart murmurs than others? 

Certain breed dogs have an increased risk of developing patent ductus arteriosus (PDA), which often causes continuous heart murmurs. These breeds include: Maltese, Pomeranian, Poodle, German Shepherd, Chihuahua, Bichon Frise, and Keeshond.

How do I treat my dog’s heart murmur?

Your vet will determine the best course of action for addressing a heart murmur in your dog. This will depend on the type and severity of the murmur.

Can heart murmurs be prevented?

The short answer: not really. Heart murmurs themselves cannot be prevented, but you can lower your dog’s risk for developing some conditions that cause them – such as heart disease – by promoting a healthy lifestyle.

Did you know

  • Heart murmurs are not conditions within themselves. They are symptoms caused by heart abnormalities or other medical conditions.
  • Not all heart murmurs are dangerous to your dog’s health. Innocent heart murmurs require no treatment, and most dogs grow out of them over time.
  • Pumpkin plans cover 90% of eligible vet visits — making it easier for you to provide your pet the best possible care if accidents and illnesses arise. Fetch a quote today!

Caitlin McQuade

Caitlin is a writer and the proud roommate of an adorable and elusive cat named Olive.
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