Pet Care Blog

Heart Murmur in Dogs: Everything You Need to Know

Dr. Ricky Walther
Dog examined by vet with stethoscope

When veterinarians diagnose a dog with a heart murmur, many pet parents understandably begin to panic. While heart health is always important, you should know that not all murmurs are equally serious. Additionally, many dogs with heart murmurs have underlying medical conditions that can be treated.

Keep reading to find out more about the symptoms, diagnosis, and treatment options for heart murmur in dogs.

Table of Contents:

Pro Tip: A pet insurance policy can cover a portion of the cost for treatments related to heart diseases and abnormal murmurs, so long as the condition is not pre-existing conditions at the time of enrollment. That's why it's important to sign up for a policy while your pet is young and in good health.

What is a heart murmur in dogs?

Heart murmurs are abnormal heart sounds or vibrations caused by disturbed blood flow within the dog's heart. It isn’t a condition on its own, but rather a symptom of another underlying medical issue.

A heart murmur is not exclusively associated with older dogs and can start at any age. In fact, some dogs are born with a certain type of murmur, while others develop them when they get older.

If the heart murmur is severe enough, it can be heard and even felt when you lay your hand over your pup’s heart. If you suspect your dog might have a heart murmur, seek the medical expertise of your vet. They will listen to your pet’s heart and recommend the best course of treatment.

Types of heart murmurs in dogs

Veterinarians distinguish three different types of heart murmur based on when the sound is heard during the heart cycle:

  • Systolic heart murmurs represent the majority of canine cases and take place during the systole phase as the heart muscle contracts.
  • Diastolic murmurs are very rare in dogs, but they take place when the heart muscle relaxes between two heartbeats.
  • Continuous murmurs (also known as to-and-fro murmurs) happen throughout a dog's regular cardiac cycle.

Heart murmur grades

Heart murmurs also differ by loudness, which reflects the amount of disturbance present in the heart. Veterinarians grade canine heart murmurs on a scale of 1 (mild) to 6 (severe):

  • Grade 1 heart murmurs are very quiet and can barely be detected with a stethoscope. This type of murmur is only heard intermittently, typically in one location on the chest.
  • Grade 2 is quiet, but can be easily heard with a stethoscope.
  • Grade 3 heart murmurs have intermediate volume that is consistently heard.
  • Grade 4 consists of loud murmurs that can be heard on both sides of the chest.
  • Grade 5 murmurs are quite loud and is easily heard with a stethoscope. It can also be felt by placing your hand against the dog’s chest.
  • Grade 6 is a very loud murmur that can be heard and even felt without a problem when you place a hand on the dog’s chest. It can also heard with a stethoscope placed a few inches off of the body wall.

It should be noted that the loudness of the murmur is not always directly correlated with the severity of the disease.

Heart murmur configurations

The heart murmur configuration (also called quality of the murmur) describes the way the murmur sounds. There are four types of heart murmur configurations.

  • Plateau murmurs have uniform loudness and are typically associated with aortic regurgitation.
  • Crescendo-decrescendo heart murmurs grow louder and then softer, with common associations to pulmonic or aortic stenosis.
  • Decrescendo heart murmurs start loud and then get quieter. They’re typical of diastolic murmurs and are commonly associated with a ventricular septal defect or aortic regurgitation.
  • Continuous murmurs, also called machinery quality murmurs, are associated with a congenital heart defect called patent ductus arteriosus.

Tired Golden Retriever dog lying down on the floor

What causes a heart murmur in dogs?

In dogs, murmurs can be caused by actual damage or changes within the heart. Abnormal stretching of the heart muscle, faulty valves, narrowing of the veins or arteries, dilated heart chambers, holes in the heart walls, tumors, or other structural abnormalities can all create blood turbulence and result in a murmur. Heart murmurs can be congenital (i.e. the dog is born with it) or acquired later in life.

In some cases, a heart murmur can be caused by a variety of medical conditions that are not related to the heart. These heart murmurs are usually quiet, intermittent, and often resolve after treating the underlying medical condition.

Here is a list of conditions that can cause a heart murmur in dogs:

  • Anemia
  • Atherosclerosis
  • Cardiomyopathy
  • Dysplasia
  • Endocarditis
  • Endocardiosis
  • Heartworm disease
  • Hyperthyroidism
  • Pulmonic stenosis
  • Other valvular stenosis
  • Tumors
  • Tetralogy of Fallot

What are innocent heart murmurs?

Innocent or physiologic heart murmurs are murmurs that are not associated with heart disease. This type of heart murmur is often caused by blood moving or circulating rapidly through the heart and doesn’t impact the dog’s health or lifespan.

Innocent heart murmurs are common in puppies and usually appear at six to eight weeks of age. Research has found that about 20% of young puppies will have an innocent heart murmur at one of their early check-ups and, in many cases, the murmur might simply be due to the puppy’s position when the vet was listening. It can also occur in puppies who have an unrelated disease (like a respiratory tract infection or anemia) or when the puppy is overly excited.

This type of heart murmur is benign and puppies usually outgrow it by five to six months of age. In general, innocent heart murmurs have a low intensity (usually Grade 1 or 2) and don’t cause any clinical signs.

Brown puppy held close to chest

What are the symptoms of a heart murmur in dogs

Many dogs with a heart murmur don’t show any signs of illness. In general, whether your dog will show symptoms or not will depend on the severity of the murmur.

Oftentimes, dogs will start showing symptoms later in adulthood, when the heart and circulatory system begin to struggle to keep a proper blood flow. This is known as congestive heart failure. The specific heart murmur in dogs symptoms will depend on which part of the heart is failing, but they usually include:

  • Difficulty breathing
  • Hacking cough
  • Inability to exercise
  • Weakness or lethargy
  • Distended abdomen or bloated appearance
  • Pale gums or mucus
  • Fainting, or collapse

In puppies, symptoms of heart murmur can include poor growth. This means that the pet will be thinner and smaller than other pups their age. The puppy might also get tired more easily or won’t be as active as other young animals.

Early detection is key, which is why annual wellness check-ups with your vet are so important.

How to diagnose heart murmur in dogs

Heart murmurs in dogs are usually diagnosed with a stethoscope. Your vet will listen to your pup’s heart, and determine the type and grade of murmur based on its loudness and where it’s coming from.

Once the vet identifies the murmur, they will proceed to diagnose the cause. In order to narrow down the list of potential causes, the vet will likely ask you questions about your pet’s overall health, medical history, and take into consideration their breed and age.

For instance, some conditions like heartworm disease can predispose a pup to health issues later in life, plus some dog breeds (such as Cavalier King Charles Spaniels, Dachshunds, and Miniature Poodles) are more prone to heart abnormalities.

Diagnosing the underlying condition might require additional testing. Depending on the symptoms your dog is showing, the vet might recommend dog x-rays, blood tests, an echocardiogram, and an ECG to see if severe heart disease is present.

German Pointer dog examined by vet with stethoscope

How to treat heart murmurs in dogs

When it comes to dog heart murmur treatment, it should be noted that what you’re actually treating are the symptoms and issues associated with the condition. This is because murmurs are usually caused by an underlying medical issue, so the treatment for your pet will depend on the diagnosis.

Heart murmur treatment options may include oral medications, specialized diets, and supportive care. Certain congenital heart defects like patent ductus arteriosus and pulmonic stenosis can be corrected surgically.

In many cases, especially in puppies and younger dogs with low-grade murmurs, the condition may go away on its own. Innocent murmurs don’t require treatment but they should be monitored. If your pup’s murmur doesn’t improve with time, this could be an indicator the murmur is not innocent and needs to be addressed.

Pro Tip: Treating a dog with a heart murmur can be very expensive, and without adequate pet insurance, the costs will soon mount up. In order for your dog to be covered for a heart murmur condition, you’ll need to have a pet insurance policy in place before it’s diagnosed.

What is the life expectancy of a dog with a heart murmur?

A heart murmur can be serious and be a warning sign of future congestive heart failure, but that doesn’t mean you need to panic as many of the conditions that cause a heart murmur can be treated. However, in more serious cases, especially with senior dogs, the prognosis might be less optimistic.

The severity of the murmur will depend on several factors and only your vet will be able to determine how serious a heart murmur is for your dog. Some pups can live their entire life with a murmur and experience no issues, but if the condition is associated with underlying heart disease, it can be fatal. In fact, the dog is at risk for developing congestive heart failure if the disease becomes severe.

As every heart murmur is unique, it’s best to consult with your vet about the prognosis for your pet.

Key Takeaways

  • Heart murmurs in dogs are abnormal sounds made by the canine cardiovascular system. Some dog heart murmurs can be a sign of underlying disease, while others might not cause any long-term health issues.
  • Many dogs with a heart murmur don’t show any symptoms while others may cough, have difficulty breathing, or feel lethargic.
  • The heart murmur treatment for dogs will depend on whether there’s an underlying heart disease along with the condition.
  • Consult your vet if you have more questions about heart murmur in dogs.

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Ricky Walther, DVM

Dr. Ricky Walther

Ricky Walther, DVM, is a small animal general practitioner in the greater Sacramento, California area. Realizing the positive financial and medical impact that pet insurance can provide for pet parents and the profession, he lends support and advice to companies like Pawlicy Advisor "The Pet Insurance Marketplace") that simplify the process of connecting with veterinary financing resources.

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