Heart Murmurs in Dogs: Symptoms, Causes, and Treatment
Key takeaways:
A heart murmur is an abnormal sound a dog’s heart makes when the blood isn’t flowing properly.
Conditions that can cause heart murmurs in dogs include birth defects, heart disease, and stress.
Treatment for a heart murmur depends on the underlying cause. Medication or a special diet might be necessary.
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When a vet frowns while listening to your dog’s heart during a routine visit, it can be scary. And if they say your dog has a heart murmur, you probably have questions about what that is and what it means for your pup.
Heart murmurs aren’t always emergencies. But it’s good to know if your dog has one, so that you can keep an eye on their heart health. We’ve got answers to your questions, so keep reading.
What does it mean when a dog has a heart murmur?
A heart murmur is an abnormal sound veterinarians can hear through a stethoscope when they listen to your dog’s heart. A dog’s heart normally makes a consistent noise when it pumps blood. The abnormal sound comes from blood that’s not flowing properly through the heart. A murmur is often described as having a whooshing sound.
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Heart murmurs in dogs could indicate heart disease. But sometimes heart murmurs are benign, or harmless.
What are the symptoms of heart murmurs in dogs?
Dogs may not show signs of having a heart murmur. You may not even know your dog has one until your veterinarian hears it during an exam.
But you may notice signs of the underlying causes of heart murmurs, such as:
Breathing problems
Lack of energy
Pale gums
Weight loss
Collapse
A veterinarian will use what they hear and any noticeable symptoms to determine the next steps for your dog.
What causes heart murmurs in dogs?
Heart murmurs in dogs can be caused by a number of underlying health conditions.
Heart disease
Heart disease is a common cause of heart murmurs in dogs. About 10% of dogs will develop heart disease in their lifetime. Mitral valve disease is the most common type of heart disease in dogs.
Treating heart disease: Heart disease is common in dogs. If your dog gets a diagnosis, check out all your potential treatment options.
Maintain a healthy weight: Overweight dogs are at risk for several health conditions, including heart murmurs. Learn how to help your pup lose weight safely.
Need to change your dog’s food? It’s best to make the switch gradually over 5 to 7 days. Here’s a schedule you and your dog can follow.
Congenital murmurs
Some dogs are born with a heart murmur, which is called a congenital murmur. There are several common congenital conditions that can cause heart murmurs. Some dog breeds are more likely to be born with these issues than others.
Dog breeds more prone to a heart condition and murmurs include:
Beagles
English bulldogs
Chihuahuas
Spaniels
Poodles
Labrador retrievers
Golden retrievers
Collies
Yorkies
Terriers
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Structural heart issues
Heart murmurs can can be caused by a structural problem in your dog’s heart, such as:
A heart valve that doesn’t open and close correctly
A hole between areas of the heart
Parts of the heart being unusually narrow
Vibrations occurring within the heart
Issues outside the heart
Other causes come from outside the heart and are not related to heart disease. These include:
Anemia or thin blood
Excitement or stress, which makes the heart beat faster and harder
Low protein in the blood (hypoproteinemia)
Low weight
Bacterial infection
Heart valves can become infected when bacteria gets into the bloodstream. This is called endocarditis. It can also cause heart murmurs in dogs. The bacteria can come from things like a wound or dental disease.
Heart murmurs in puppies
Murmurs caused by issues that don’t directly involve the heart are generally considered harmless, especially when an underlying cause can’t be found. Benign heart murmurs are more common in puppies than in adult dogs. In puppies, the murmur usually goes away by the time they’re 12 to 15 weeks old.
How are heart murmurs diagnosed?
Heart murmurs are diagnosed based on what your veterinarian hears while listening to your dog’s heart. Veterinarians can get an idea of the severity of a dog’s heart murmur based on the type of sound they hear and the location of the sound. But this is not enough to make a diagnosis.
Your dog’s heart murmur might be given a grade. The grading system describes how loud a heart murmur is, with louder murmurs getting higher grades. But a high grade doesn’t always indicate severe heart disease. A veterinarian will help you interpret any grade your dog’s heart murmur might receive.
Heart murmur tests
If your dog doesn’t have other symptoms — such as lack of appetite or breathing problems — a veterinarian might just keep an eye on the heart murmur. If you decide to pursue a diagnosis, a vet might recommend various tests.
These tests could include:
Electrocardiogram (ECG)
Ultrasound
X-rays
Blood and urine tests
Heart ultrasounds — also known as echocardiograms — are usually best for determining the specific location of heart murmurs. They allow veterinarians to see any abnormal blood flow that may be causing the murmur. Typically, you’ll need to see a veterinarian cardiologist (a heart specialist) for the ultrasound.
If a disease is suspected to be the underlying cause, a vet might run more blood and urine tests. Dogs with heart disease usually have lowered functioning in their liver and kidneys.
What are heart murmur grades in dogs?
Once a veterinarian determines your dog has a heart murmur, they will grade the murmur. A grade helps vets determine how severe the heart murmur is. There are six heart murmur grades:
Grade 1: Murmur is very soft and hard for veterinarians to hear, even with a stethoscope. This murmur is the least severe.
Grade 2: A heart murmur that can be heard faintly, and it’s usually heard only in a specific area of a dog’s heart.
Grade 3: A veterinarian can easily hear the murmur, as long as they are listening near the murmur’s location in the heart.
Grade 4: This murmur is loud and obvious when a veterinarian begins listening to a dog’s heart.
Grade 5: The murmur sounds very loud, and a veterinarian can feel the murmur when they place their hands over it.
Grade 6: This murmur is the most severe. It is incredibly loud and can still be heard even when a veterinarian listens away from your dog’s chest. Grade 6 murmurs can also be felt when a vet presses above the murmur.
How are heart murmurs treated in dogs?
Treatment for heart murmurs in dogs depends on the underlying cause if one can be found. If your dog is diagnosed with a certain disease or condition, they may need:
Antibiotics for endocarditis
A special diet
Medication
Supportive care
Surgery
Other factors that could determine treatment are your dog’s age and the cost of treatment. A veterinarian will go over your options.
A benign heart murmur typically won’t require treatment. But a veterinarian will likely continue to monitor it as your dog ages.
What is the life expectancy of a dog with a heart murmur?
The life expectancy of a dog that has a heart murmur caused by heart disease can vary. It depends on the underlying cause of the murmur and the severity of disease.
For example, dogs with benign heart murmurs usually have a normal life expectancy. But dogs with heart disease may live only months to years, depending on the severity of their condition.
Heart diseases like mitral valve disease are usually managed with long-term medication to provide a good quality of life for as long as possible. But mitral valve disease is a progressive condition, and it can’t be cured with medication.
The other symptoms your dog may have alongside their heart murmur can also affect their life expectancy. For instance, dogs with dilated cardiomyopathy have a shorter life expectancy if they have other symptoms in addition to their heart murmur.
A veterinarian will likely want to monitor your dog’s condition frequently, especially if they develop symptoms of heart failure.
Frequently asked questions
How much it costs to treat a heart murmur in dogs depends on what causes the murmur. Heart murmurs are caused by underlying conditions, such as heart disease or a condition dogs are born with.
At the very least, you can expect to pay for a veterinary exam and likely testing such as bloodwork or an echocardiogram. After that, you may need to pay for follow-up appointments, tests, and treatment.
Ask a veterinarian what you can expect to pay to treat your dog’s murmur.
Yes, it is OK to walk a dog with a heart murmur. Depending on the cause of your dog’s murmur, a veterinarian may recommend shorter walks or avoiding certain types of exercise. But overall, walking your dog is still good for their health even with a heart murmur.
Ask a veterinarian if there are foods you shouldn’t feed your dog if they have a heart murmur. There’s some evidence that a lower salt diet may help dogs with certain types of heart disease.
It’s best not to feed your dog a grain-free diet. Grain-free diets have been linked to a type of heart disease called dilated cardiomyopathy.
Some heart murmurs in dogs are genetic. These are called congenital heart issues, and dogs are born with them. Common types of congenital heart conditions include:
Pulmonic stenosis
Ventricular septal defect
Subaortic stenosis
Tricuspid valve dysplasia
The bottom line
A dog may develop a heart murmur when blood doesn’t flow through the heart correctly. Heart murmurs in dogs can be caused by a number of conditions, such as heart disease or a congenital health issue. Sometimes, heart murmurs in dogs can be harmless. Murmurs caused by stress, excitement, or anemia are usually considered benign.
A veterinarian will run diagnostic tests — like blood work — to figure out the cause of your dog’s heart murmur. They may also refer you to a specialist for an ultrasound. Depending on what they find, your dog’s murmur might require medication, a special diet, or surgery.
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References
Cornell Richard P. Riney Canine Health Center. (n.d.). Get a jump on heart murmurs. Cornell University College of Veterinary Medicine.
Fox, P. R. (2014). Managing congestive heart failure. World Small Animal Veterinary Association Congress Proceedings.
Häggström, J. (2008). Prognostic variables in canine mitral valve disease. World Small Animal Veterinary Association World Congress Proceedings.
Häggström, J. (2017). Dilated cardiomyopathy in dogs - an update. World Small Animal Veterinary Association Congress Proceedings.
Keene, B. W., et al. (2019). ACVIM consensus guidelines for the diagnosis and treatment of myxomatous mitral valve disease in dogs. Journal of Veterinary Internal Medicine.
Kittleson, M. D., et al. (2024). Diagnosis of heart disease in animals. Merck Veterinary Manual.
NC State College of Veterinary Medicine. (n.d.). Cardiology: Degenerative mitral valve disease.
Reagan, K. L., et al. (2022). Outcome and prognostic factors in infective endocarditis in dogs: 113 cases (2005-2020). Journal of Veterinary Internal Medicine.
Richman, J. A. (2000). Your dog & heart disease. Veterinary Information Network.
Rishniw, M. (2023). Heart murmurs in dogs and cats. Veterinary Partner.
Rishniw, M. (2024). Mitral valve disease in dogs and cats. Veterinary Partner.
U.S. Food and Drug Administration. (2022). FDA investigation into potential link between certain diets and canine dilated cardiomyopathy.
