Heart murmurs in dogs may be identified during routine exams when a veterinarian uses a stethoscope to listen to a dog's heart. If your dog has a heart murmur, instead of hearing the usual "lub-dub" sound, your vet may hear a "whoosh" sound. Not all causes of dog heart murmurs are a cause for concern; however, if your vet notices one in your dog, it's important to know what's causing the murmur and whether the condition needs to be treated. Here's more on what heart murmurs are, what causes them and how they can be treated.

What Is a Heart Murmur in Dogs?

When your veterinarian listens to your dog's heart with a stethoscope, part of what they listen for is a classic "lub-dub" sound that suggests that your dog's heart valves are opening and closing properly. These heart valves open and close in a synchronized manner that allows blood to be pumped to the lungs and the rest of the body without ever flowing in the wrong direction. However, whenever blood flows the wrong direction through the heart, which can be due to things such as impaired heart valve function or heart muscle defects, vets will hear this as a turbulent "whoosh" sound, also known as a heart murmur.

Vets identify heart murmurs based on the intensity of what they hear when they listen to the heart — a "1" rating would indicate the softest murmur while a "6" would be rated as the loudest. However, the volume of the murmur has no correlation with the severity of the condition causing the murmur; it's simply one method that vets use to record the murmur over time to see if it changes.

While heart murmurs may be indicative of heart disease or other conditions, they aren't always a cause for concern. For example, puppies may have an "innocent heart murmur" that they're born with. But, once they're about four months old, the murmur disappears without any treatment. In contrast, a heart murmur in a senior dog may be due to a valve disease, requiring vet treatment and monitoring. Depending on the cause of the heart murmur, your vet may elect to monitor your dog or may recommend additional testing and treatment.

Causes of Dog Heart Murmurs

Anything that causes abnormal blood flow within the heart can cause a murmur. Here are the most common causes of heart murmurs in dogs:

  • Leaky heart valve: A dog's heart has four chambers: left and right atria, and left and right ventricles. In between these chambers are valves that open and close to let blood flow normally through the heart. Leaky valves in the heart are the most common cause of heart murmurs in dogs. Common breeds at risk for this disease include Cavalier King Charles Spaniels, cocker spaniels, poodles and chihuahuas.
  • Heart Muscle Disease (Cardiomyopathy): In dogs, this is most often caused by a weakening of the heart muscle's walls, resulting in turbulent blood flow and a murmur. Breeds at risk for this condition include Dobermans, boxers and giant breed dogs.
  • Cancer: A tumor anywhere inside the heart can cause turbulent blood flow and a murmur.
  • Congenital heart defects: There are a wide variety of congenital heart defects in dogs that can result in heart murmurs. A few of the more common congenital heart defects include: patent ductus arterious (PDA), which is seen in many breeds including German Shepherds, Maltese, poodles and Yorkshire Terriers; pulmonic valve stenosis (narrowing), which is commonly seen in English Bulldogs; and aortic valve stenosis (narrowing), which may be seen in breeds such as Golden Retrievers and Rottweilers.

Clinical Signs of a Heart Murmur in Dogs

Unless a dog is experiencing heart failure, there are often no signs associated with heart murmurs in dogs. In fact, many dog parents are surprised when their vet detects a heart murmur during a routine physical exam. If a dog has been diagnosed with a heart murmur, be aware of the clinical signs of heart failure, which can include:

  • Excessive tiredness or sleeping more
  • Cough
  • Rapid breathing, panting more, or breathing that sounds wet or congested
  • Fainting or collapsing
  • Pale or blue gums
  • Potbellied appearance
  • Weight loss

If you notice your dog showing any of these clinical signs, call your vet for advice immediately.

Diagnosing a Heart Murmur in Dogs

If your vet hears a murmur when they listen to your dog's heart, be prepared for additional testing. The most common test is a chest X-ray. This allows your vet to look at your dog's heart, lungs and pulmonary vessels, and it may assist in a diagnosis. However, only an echocardiogram (ultrasound of the heart) can confirm the source of a heart murmur as well as the characterization of the severity of the heart disease present. Additional tests that may be recommended based on your dog's individual case include bloodwork (internal organ function screen, complete blood count and heartworm test), blood pressure monitoring and an electrocardiogram (ECG) to check the electrical activity of your dog's heart.

Treating a Heart Murmur in Dogs

Treatment of heart murmurs in dogs depends on what's causing the murmur and whether it's negatively impacting your dog's life. If your dog isn't showing any signs of heart disease, there may be no treatment recommended. Your vet may elect to monitor your dog every couple of months and only treat your dog if they notice any clinical signs. If your dog was diagnosed with a heart murmur that's caused by a condition that can be corrected surgically, such as a PDA, then surgery will be recommended. If the heart murmur is due to anemia or heartworm disease, then that condition can be treated as well.

Leaky heart valves are managed with medication to help the heart pump blood more effectively. Dogs with many forms of heart disease can live reasonably normal lives as long as you know the signs that indicate your dog's heart needs some help (see above), give medications as prescribed and work with a vet you trust.

While having a heart murmur diagnosed in your dog may sound scary, it doesn't need to be. Many times, your vet can resolve the situation for you or work with you to maximize your dog's health and wellbeing. Your job as the pet parent is to stay informed and continue to bring your furry companion to your vet for routine exams.

Dr. Sarah Wooten Dr. Sarah Wooten

Dr. Sarah Wooten graduated from UC Davis School of Veterinary Medicine in 2002. A member of the American Society of Veterinary Journalists, Dr. Wooten divides her professional time between small animal practice in Greeley, Colorado, public speaking on associate issues, leadership, and client communication, and writing. She enjoys camping with her family, skiing, SCUBA, and participating in triathlons.

Related articles

Dog Not Pooping or Peeing?

Learn what to do if your dog is experiencing constipation or an inability to pee. If he isn't going at least twice a day, learn what steps you should take.

How to Build a DIY Dog Ramp

Learn how to simply and inexpensively build a DIY dog ramp to help your dog get up & down more easily (great for senior dogs & those with mobility issues).

How to Handle Your Dog's Fear of Water & Bathing

Discover helpful tips for managing a dog who's afraid of water, how to handle bath time, and how to get them more comfortable with swimming.

Is Your Dog a Carnivore or an Omnivore?

Learn about the different classifications between carnivores and omnivores to decide which order dogs fall under.

Why Do Dogs Hate Baths? (& Tips for Bathing a Scared Dog)

Learn why some dogs hate baths so much, as well as the importance of bathing and tips for comforting a scared dog when it's time to take a bath.

Common Causes of Dog Skin Conditions

Understand the common irritants that cause various dog skin conditions, whether they be due to parasites, infections, food, or the environment.

Dwarfism in Dogs: Types, Health Concerns & Breeds It Affects

Learn about dwarfism in dogs, including types of this condition, breeds that are prone to developing it & general effects dwarfism has on a dog's health.

Pyoderma in Dogs: What You Need to Know

Learn what pyoderma in dogs looks like, what causes it and how nutrition & your dog's food can play a role in preventing and treating the infection.

Tapeworms in Dogs: How Dogs Get Them & Getting Rid of Them

Learn how common tapeworms in a dog are, how to spot the signs of tapeworms on your dog (or in their poop), and tips about prevention & treatment.

Can My Dog Eat Spicy Food?

Find out if you can feed your dog spicy food or add some spicy flavor to his dog food, and any health implications of doing so.

Do Dogs Need Shoes & Booties in Summer Heat?

Discover scenarios where dogs can benefit from shoes or booties in extreme summer heat, including environmental concerns & tips for finding the right ones.

Tips for Socializing an Older Dog

Socializing an older dog is usually more challenging than socializing a puppy. Learn how to overcome the challenges to safely socialize an adult dog.

Can Dogs Eat Cheese?

Learn whether cheese is a snack that's safe for your dog, including specific types of cheese, ingredients to watch for and how much is ideal.

The Importance of Exercise for Your Puppy

Find out why exercising is so important to your puppy's overall healthy by reading through these 4 helpful facts.

"Why Is My Dog Constipated?" and Other Gastrointestinal Questions

Wondering why your dog is constipated? Or why he has diarrhea? Learn more about these common gastro issues in dogs, and tips for managing them at home.

When Does My Puppy Become an Adult Dog?

Learn how to recognize the signs that your puppy is becoming an adult dog, as well as how you can help meet their developmental & nutritional needs.

Dealing With Ear & Skin Yeast Infections in Dogs

Learn helpful information about yeast infections in dogs (in both ears & skin), including signs of the condition, causes, treatments and prevention tips.

Why Is My Dog Afraid of the Dark?

Discover common reasons why your dog seems afraid of the dark, including things like separation anxiety & traumas, and how to help reduce their fears.

A Dog's Memories: Do They Remember Their Owners?

Discover what types of memories dogs actually have, how their memories work & how long they last, and whether they remember details about their owners.

Dog Eye Boogers, Goop & Gunk: When Should You Be Concerned?

Learn about dog eye boogers, goop, gunk & crustiness: when it's normal vs. when it could be a health concern and which breeds & sizes are most susceptible.