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

Veterinarian Talks Through Heart Murmurs in Dogs | BetterVet


Around 1 in 10 dogs will develop heart disease in their lifetime, with the most common heart disease being mitral valve insufficiency. This leads to congestive heart failure. 

A heart murmur is the abnormal sound of blood flowing back into the heart through leaky valves. When a veterinarian listens to your dog's heart they should hear two parts of the heartbeat, the opening, and closing of the heart valves. When there is a backflow of blood from a leaky or damaged valve, a different sound is heard called a heart murmur. A heart murmur can be something that is detected early in life, such as at the puppy wellness checks or later in life as your dog ages. Most heart murmurs are detected later in life. 

Breeds commonly affected by heart murmurs include Cavalier King Charles Spaniels, Chihuahuas, Dashhounds, Dobermans, and Boxers.  

What causes heart murmurs in dogs? 

There are a few different causes of heart murmurs in dogs. 

In puppies, heart murmurs can be related to congenital causes (malformations in the womb). The good news is that puppies can ‘grow out’ of a heart murmur if it is mild so your veterinarian may just recommend monitoring the heart murmur as your puppy grows. 

Heart murmurs in older dogs can be related to congestive heart failure, either from valvular disease or dilated cardiomyopathy. 

Your dog can also have a heart murmur caused as a result of other illnesses such as high blood pressure or severe sudden onset illnesses such as anemia or shock from major trauma. 

What can be the symptoms of heart murmurs in dogs? 

Heart murmurs can go unnoticed for many years if your dog is not regularly checked by a veterinarian as often no symptoms are seen in early disease. This is why we strongly recommend a health check-up with a vet at least once a year to detect the early signs of disease. 

When the heart murmur is severe, common signs we see in dogs include: 

  • Lethargy 
  • Coughing
  • Increased breathing rate and effort 
  • Sudden episodes of collapse or fainting 
  • Exercise intolerance 
  • Blue or grey tinge to the gums (emergency) 

How are heart murmurs diagnosed in dogs?

Heart murmurs in dogs are first picked up when your veterinarian listens to your dog’s chest with a stethoscope. A heart murmur is graded on a scale of one to six, one being very mild and six very severe. 

Low-grade heart murmurs may be monitored by your veterinarian with regular checkups every three to six months. The veterinarian will listen to the heart again at this point and if the heart murmur is getting worse, then diagnostic tests may be advised. 

Diagnostic tests to find out more information about your dog’s heart murmurs often start with echocardiography, which is an ultrasound of the heart. This is best done by a board-certified veterinary cardiologist if there is one available in your area. The cardiologist will take measurements of the heart and look at the flow of blood through the heart. These measurements tell us how advanced your dog’s heart disease is. Medication can be prescribed to help support the heart based on these findings. 

Chest X-rays may be taken alongside the echocardiography exam. This helps the veterinarian to see signs of congestive heart failure such as fluid accumulation in the lungs, or enlargement of your dog's heart.

Further tests that may be run include ECG which measures the electrical activity of the heart and blood tests to look for other medical conditions that can be treated to help the overall health of the heart. 

How are heart murmurs treated? 

The treatment for some grades of heart murmurs may be to just monitor them if your dog is showing no obvious signs of illness associated with the heart murmur. 

If your puppy has a congenital heart abnormality, such as a PDA, surgery may be needed to fix the problem. 

Dogs who have heart murmurs related to congestive heart failure need medications to support the heart. These medications help the heart to pump blood around the body and reduce fluid build-up in the lungs. This helps your dog’s overall quality of life. Medications will need to be given daily, and often the doses of medications will need to be increased as your dog’s condition gets more advanced. 


Is a heart murmur painful?

A heart murmur in itself is not painful, but the effects of having a severe heart murmur such as pulmonary edema (fluid on the lungs) can be stressful, which is a similar sensation to pain. 

Can my dog still exercise regularly with a heart murmur? 

The severity of the heart murmur dictates how much exercise is okay for your dog. For low-grade heart murmurs, exercise can continue as normal. For high-grade heart murmurs and dogs with congestive heart failure, gentle short walks only are advised. 

What can I do at home to help my dog with a heart murmur? 

The best thing you can do for your dog at home is to keep their body weight within a normal range. Extra weight carried by your dog puts extra pressure on their joints, heart, and overall health. Talk to your veterinarian about a weight loss diet if you think your dog is overweight. 



A heart murmur can go undetected for many years and cause your dog no issues. With high numbers of dogs suffering from heart disease at some point in their life, it’s worth keeping an eye out for heart disease early on in their life through regular health checks with your veterinarian. This means medications can be started sooner, which slows down the progression of the heart disease and prolongs the time that your dog has left to enjoy with you. Keeping your dog healthy, fit, and not letting your dog get overweight will improve heart health. If you would like more advice on how to do this or anything else covered in this article, talk to our BetterVet veterinarian today. 


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