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Heart Murmurs in Dogs

Heart Murmurs in Dogs

Jun 03, 2021
AUTHOR Dr. Addie Reinhard, DVM

Reviewed by Dr. Addie Reinhard, DVM

Dr. Addie Reinhard is an experienced companion animal veterinarian with a passion for providing reliable veterinary insight & expert advice to help pet parents better care for their pups.


  • A heart murmur can be defined as an abnormally sounding heart.
  • A heart murmur in dogs is often detected on physical examination and heart auscultation with a stethoscope by a veterinarian.
  • Some heart murmurs can be a sign of heart disease, but some heart murmurs may not cause any long-term health problems.
  • Your pet may not be experiencing any symptoms from their heart murmur, but if they are experiencing coughing or difficulty breathing, this may be a sign of heart disease.

  • The treatment for a heart murmur depends on if there is underlying heart disease along with the murmur.

What is a heart murmur in dogs?

A heart murmur in dogs is defined as an unusual or abnormal heart sound. These abnormal sounds can usually be heard by a veterinarian when they listen to the heart with their stethoscope. Normally, the heart makes a regular “lub-dub” sound. If the veterinarian hears any other abnormal sounds when listening to your dog’s heart, they may diagnose a heart murmur.

What breeds of dogs are prone to heart murmurs?

Certain dog breeds may be more predisposed to developing heart murmurs and heart disease. Any size of dog breed can get a heart murmur, though, in my experience as a veterinarian, heart murmurs in dogs are more common in small breed dogs. PetMD reported that heart disease is most common in:

  • Cavalier King Charles Spaniels
  • Miniature Poodles
  • Toy Poodles
  • Dachshunds
  • Boxers
  • Doberman Pinschers
  • Miniature Schnauzers
  • Golden Retrievers

What causes heart murmurs in dogs?

There are many potential reasons that your dog may have a heart murmur. Some murmurs are considered innocent murmurs meaning there is not an underlying disease causing the murmur. The AKC reported some of the most common causes of heart murmurs are:

  • Low red blood cell count (anemia)
  • Heartworm infection
  • Heart disease
  • Dilated cardiomyopathy
  • Heart failure
  • Infection of the heart valves
  • Innocent murmur

What is a puppy heart murmur?

As puppies are developing and growing rapidly, they may occasionally develop a heart murmur. Most commonly, heart murmurs in puppies do not have an underlying cause and will not affect your puppy’s health. These are called innocent or physiologic heart murmurs. On the other hand, a heart murmur in a puppy could indicate a birth defect of the heart. Your veterinarian may recommend an echocardiogram to determine the underlying cause of the heart murmur or they may recommend waiting and watching. Usually, an innocent murmur will go away by 4 to 6 months of age.

Symptoms of Heart Murmur in Dogs

If your pet has a heart murmur, this doesn’t mean that they automatically have heart disease. Some pets may not have any symptoms from their heart murmur. Other pets with heart murmurs may have underlying heart disease which can cause mild to severe respiratory symptoms.

What are the symptoms of a dog with heart problems?

The most common signs that your dog’s heart murmur may be associated with heart disease include coughing and difficulty breathing. If your dog is coughing excessively or if the cough sounds moist or wet, this could be a sign that your dog has heart disease. ASPCA Pet Health Insurance reported that the most common signs of heart disease in dogs include:

  • Coughing
  • Difficulty breathing
  • Shortness of breath
  • Rapid breathing
  • Weight loss
  • Passing out or fainting
  • Exercise intolerance or getting tired easily

If your dog is having trouble getting on and off furniture due to a heart murmur, heart disease, or old age, consider getting your pup a PawRamp. The Alpha Paw PawRamp is designed to help your dog get safely up and down from the furniture.

Heart Murmur Grades in Dogs

There are six grades of heart murmurs in dogs. Grade I heart murmurs are the quietest and grade VI heart murmurs are the loudest. The following list describes what each grade of heart murmur means for your dog:

  • Grade I heart murmur: Very quiet murmur that is barely detectable even with a stethoscope.
  • Grade II heart murmur: Soft murmur that can be heard with a stethoscope.
  • Grade III heart murmur: Moderate loudness murmur.
  • Grade IV heart murmur: Loud murmur.
  • Grade V heart murmur: Loud heart murmur that you can also feel with your hand.
  • Grade VI heart murmur: Very loud heart murmur that can be heard with the stethoscope held slightly away from the chest.

How is a heart murmur in dogs treated?

The treatment for a heart murmur in dogs depends on if there is an underlying condition causing the heart murmur. Your veterinarian may recommend running a few diagnostic tests to determine if there is an underlying reason for the murmur. The most common tests your veterinarian may recommend include:

  • X-rays of the chest
  • Echocardiogram or ultrasound of the heart
  • ECG
  • Heartworm test
  • Blood work

Once your veterinarian has determined the underlying cause for the murmur, they may recommend monitoring, or they may recommend medication to treat the underlying cause for the murmur.

How serious is a heart murmur in a dog?

The severity of a heart murmur can depend on a variety of factors. Some heart murmurs can be very mild while others can be potentially fatal. Only your veterinarian will be able to determine how serious a heart murmur is for your dog.

Will a heart murmur kill my dog?

Some dogs can live their entire life with a heart murmur and have no problems. Other dogs may have underlying diseases associated with their heart murmurs. A heart murmur can be potentially fatal if it is associated with heart failure and underlying heart disease.

Can a dog live with a heart murmur?

This depends on the severity of the heart murmur. If your dog has a very serious heart murmur and underlying disease of the heart, your dog may not be able to live very long with this condition. If your dog has a physiologic murmur or an innocent murmur with no underlying diseases, they may live a long and normal life. As every heart murmur in dogs is unique, it is important to consult with your veterinarian about the prognosis for your dog.

author image

Dr. Addie Reinhard, DVM

Member of Alpha Paw’s Board of Pet Experts

Dr. Addie Reinhard is an experienced companion animal veterinarian who lives in Lexington, KY with her husband, greyhound, and four cats. She graduated from the University of Tennessee College of Veterinary Medicine, and currently practices in the central Kentucky region. Dr. Addie has special interests in preventative care, dermatology, and diseases, and she enjoys creating helpful educational resources related to these topics to help pet parents keep their four-legged family members happy and healthy. We love Dr. Addie’s passion for providing reliable veterinary insight and medical advice to help pet parents like us give their pups the happy & healthy lives they deserve!

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