Heart Murmur In Dogs: When It’s Serious

heart murmur in dogs
Post At A Glance

If your vet tells you your dog has a heart murmur, what do you do next?  Heart murmurs in dogs can be harmless and may not need to be treated … or they can mean your dog has serious heart disease.  As it turns out, vets can’t always tell the difference. 

What Is Heart Murmur In Dogs

Your dog’s heart pumps blood around her body and lungs. The heart has four chambers (called atria and ventricles), with valves that separate the chambers. Here’s how it works: 

  • The right atrium receives blood from the body and passes it through the tricuspid valve to the right ventricle.
  • The right ventricle sends the blood through the pulmonic valve to the lungs, where the blood collects oxygen. 
  • The left atrium receives the blood from the lungs and passes it through the mitral valve to the left ventricle.
  • The left ventricle sends the blood throughout the body via the aortic valve. 

Normally, this blood flow is smooth. The usual heartbeat your vet hears through a stethoscope is a “lub-dup” sound.  The lub and dup are regular and of equal loudness. Those regular sounds mean the blood flows in one direction. The valves close cleanly, with a tight seal. But sometimes the valves don’t seal, so they allow blood to leak backwards. Your vet will hear a whoosh after the lub-dup … and that’s the sound of a heart murmur.

Murmurs can be systolic, meaning they happen when the heart muscle contracts. Or they may be diastolic, when the heart muscle relaxes. But some murmurs and continuous or to-and-fro murmurs that happen during all parts of the flow.

So how do you find out if your dog’s heart murmur is benign or life-threatening? And depending on that answer, how will it affect your dog’s life … and what are the treatment options?  

Innocent Heart Murmur

Puppies can be born with congenital heart murmurs that usually go away by about 6 months old. These are usually called “innocent” murmurs. They’re mild, temporary and don’t affect the dog’s overall health. Since these innocent murmurs will usually go away on their own, they’re not part of the discussion below. Treatment isn’t needed and innocent murmurs aren’t cause for concern.

But they’re not always innocent.  Some young dogs may have other symptoms that suggest a related heart problem. In that case your vet may find your puppy’s murmur needs further investigation … so he’ll approach it as he would an adult heart murmur.

Heart murmurs in adult dogs are rarely innocent.  They usually stem from underlying heart problems

How Murmurs Are Graded

Your vet should be grade your dog’s heart murmur from I to Vi based on how loud it is. This is the scale: 

  • Grade I – barely audible
  • Grade II – soft, but easily heard with a stethoscope
  • Grade III – intermediate loudness; most murmurs related to the mechanics of blood circulation are at least grade III
  • Grade IV – loud murmur that radiates widely, often including opposite side of chest
  • Grade V – very loud, audible with stethoscope barely touching the chest; the vibration can be felt through the chest wall
  • Grade VI – incredibly loud and may even be heard without a stethoscope

But the grade doesn’t tell you what’s causing your dog’s murmur – or even how serious it is.  At a lecture to vets, cardiologist Pamela Lee DVM said “The severity of the heart disease does not correlate with a loud heart murmur.”  So your vet needs to listen for the type of heart murmur for clues about the cause.

Sometimes the valve problem is mild and won’t ever cause your dog any problems. In other dogs, the leaks can cause the heart to enlarge. That leads to fluid build-up in the lungs, which is congestive heart failure. So you need to know. Ask your vet to assess what type or quality of heart murmur your dog has. They’ll need to differentiate between different abnormal heart and lung sounds … and whether the timing is related to breathing or heartbeat. 

Types Of Heart Murmur

Here are the three heart murmur qualities (also called configurations) and their likely causes … 

Plateau – uniform loudness. This is usually due to aortic valve insufficiency.

Crescendo-decrescendo – get louder then quieter. This can be a sign of aortic and pulmonic stenosis.

Decrescendo – start off loud and get quieter. They’re usually diastolic murmurs.  This type is often due to aortic valve insufficiency or ventricular septal defect. 

Continuous – also called machinery murmurs. They’re usually congenital. They’re due to blood flowing from the high pressure chamber towards a lower pressure system.

Which Dog Breeds Get Heart Murmurs?

Any dog can have a heart murmur, but they’re more common in these breeds: 

  • King Charles Cavalier (prone to degenerative mitral valve disease – DMVD)
  • Dachshund (prone to DMVD)
  • Miniature and Toy Poodle (prone to DMVD)
  • Doberman Pinscher, especially males (prone to dilated cardiomyopathy  – DCM)
  • Boxers (prone to arrhythmogenic right ventricular cardiomyopathy – ARVC)
  • Golden Retrievers (prone to aortic stenosis from improper formation of the aortic valve)
  • Miniature Schnauzers, especially females (prone to sick sinus syndrome – SSS). 
  • West Highland White Terriers (prone to SSS).
  • Cocker Spaniels (prone to SSS).

As you can see, these heart murmurs are linked to other types of heart disease. A murmur may be one of the first signs your dog has a heart condition. So how can you tell your dog has a murmur?

Signs of Heart Murmur In Dogs

A heart murmur itself may not have any clear symptoms. Instead, a heart murmur is often a symptom of a more serious heart disease. The first sign may be that your vet hears a heart murmur during a regular physical exam. But if you see some of the signs below, take your dog to the vet for a heart exam. These symptoms all indicate something more serious than just a murmur. 

  • Coughing
  • Loss of appetite
  • Exercise intolerance
  • Blue-grey tongue or gums
  • Difficulty breathing
  • Lethargy, weakness
  • Fainting or collapse
  • Pot belly

What Causes Heart Murmurs?

As you saw earlier, heart murmurs in dogs can be a sign of several different types of heart disease. These are some possible diseases linked to heart murmurs:

  • Mitral or tricuspid valve insufficiency or leakage 
  • Aortic valve insufficiency or stenosis
  • Pulmonic stenosis
  • Atrial or ventricular septal defect
  • Heart wall defects (holes, narrowing)
  • Dilated cardiomyopathy (DCM)
  • Heart arrythmia problems like ARVC
  • Endocarditis (infection in the heart valves)
  • Tumors
  • Heartworm disease

Breaking it down further … 

Dogs can also get extracardiac problems (meaning outside the heart) that cause heart murmurs. These are functional heart murmurs that don’t indicate structural heart problems. They can be due to improper blood flow caused by …

  • Anemia (low red blood cells)
  • Hypoproteinemia (low protein in blood)
  • Hyperthyroidism (unlike hypothyroidism, it’s very rare in dogs)

Anemia or hypoproteinemia may stem from a parasite infestation … like worms, fleas or ticks. Other types of infection can also cause extracardiac problems. These conditions should be manageable with treatment. 

The most common heart problem linked to heart murmurs is mitral or tricuspid valve disease. It’s more frequent in small to medium sized dogs. If this valve disease becomes chronic, it’s called endocardiosis. Often the first sign of endocardiosis is a left-sided systolic heart murmur. So your vet exam may be the first time you know your dog has symptoms of the disease. 

Valve endocardiosis can lead to fluid build-up in the lungs … which is effectively congestive heart failure (CHF). This is one of the reasons it’s so important to find out the cause of your dog’s heart murmur.

How To Find Out The Cause

When your vet hears your dog’s heart murmur, there’s a lot he can learn from listening to it through a stethoscope.  (It’s called “auscultation.”)

As your vet listens to the murmur, he’ll try to decide if it’s pathological or non-pathological. What he hears may tell him if it’s a cardiovascular problem (pathological).  Or he may find your dog’s heart is structurally normal … meaning the murmur is nonpathological, innocent or functional). 


A 2015 review in the Journal of Veterinary Cardiology in 2015 gave this warning … “A veterinarian’s ability to make this determination increases with experience in ausculting dogs …” So always get an opinion from a vet with experience in diagnosing heart disease. Ideally, consult a veterinary cardiologist.

Here are some factors your vet should be looking for …

Murmur Factors

  • Loudness
  • Intensity
  • Location
  • Whether it radiates and where to
  • Systolic vs diastolic

Other Indications

  • Mucous membrane color
  • Femoral pulse quality
  • Heart rate and rhythm
  • Breathing rate
  • Other clinical signs
  • Your dog’s age, breed and size

Diagnostic Testing For Heart Murmurs

Your vet may then move forward with other diagnostic testing, such as … 

  • X-ray
  • Electrocardiogram (ECG)
  • Arterial blood pressure
  • Lab tests, eg CBD, thyroid, plasma taurine, urinalysis, cardiac biomarkers
  • Echocardiogram

Echocardiograms are expensive but highly recommended. They’re considered the gold standard for diagnosing heart disease.  Your vet should refer you to a veterinary cardiologist for an echocardiogram. Once they confirm the diagnosis, your dog’s veterinary team will propose treatment options. 

Heart Murmur Treatments

The treatment your vet recommends will depend on the eventual diagnosis.  If it’s a low-grade, innocent or functional heart murmur, your dog shouldn’t need treatment. But there are some general natural remedies you can give to support your dog’s overall cardiac function. Keep reading to learn about those. 

Conventional veterinarians will turn to pharmaceuticals to manage serious heart disease.  Which drug your vet chooses will vary depending on your dog’s symptoms and diagnosis. There are many different drugs. They are all drugs with bad side effects … and some drugs may interact with each other. 

Even if you opt for natural treatments … eventually your dog may need pharmaceuticals to keep him comfortable. They won’t cure your dog’s heart disease … but they could help manage his symptoms. 

Drugs Used For Congestive Heart Failure (CHF)

Furosemide, a diuretic to get rid of fluid on the lungs. Some side effects and drawbacks are …

  • Sometimes ineffective
  • Changes in heart rhythm
  • Dehydration
  • Increased urination (let your dog out to pee more often!)
  • Diarrhea
  • Constipation
  • Seizures or other neurological effects
  • Apathy or weakness
  • Electrolyte imbalance
  • Dosing must be carefully managed to prevent toxicity

Pimobendan is commonly used for dogs with severe CHF or DCM. It strengthen’s the heart’s ability to contract, and dilates blood vessels.  The drug “showed promise in prolonging an affected dog’s life” up to 200 days, according to one 2012 study. Once again, there’s a long list of side effects …

  • Loss of appetite
  • Low energy
  • Vomiting
  • Diarrhea
  • Difficulty breathing
  • Kidney damage
  • Weaknes
  • Balance issues
  • Fluid buildup in the lungs or abdomen
  • Cough
  • Changes in heart rhythm

Enalapril is another drug used to treat CHF. It’s an ACE inhibitor to treat heart failure and high blood pressure. It may interact with Furosemide. Some other known side effects are …

  • Loss of appetite
  • Vomiting
  • Diarrhea
  • Tiredness or lethargy
  • Fever
  • Rash
  • Collapse or fainting
  • Weakness
  • High or low blood pressure 
  • Kidney dysfunction
  • Ulceration of the digestive tract
  • High potassium levels

These are just a few of the many drugs available to treat heart disease in dogs. At some point you may need them to help keep your dog comfortable. But there are also many natural remedies that can support your dog’s cardiac health. 

RELATED:  How congestive heart failure can be managed holistically …

Home Remedies For Heart Murmurs In Dogs

Managing your dog’s heart murmur is really about controlling his heart disease symptoms … depending on his diagnosis. It’s a very good idea to ask a holistic veterinarian for help with homeopathic or herbal remedies to manage your dog’s individual condition. Heart disease is a long-term chronic problem that will benefit from professional advice. 

Here are some remedies that are good for overall cardiac support. Ask your holistic vet about dosing for your dog’s specific condition. 

Instead of Furosemide, ask your vet if dandelion will help get rid of your dog’s fluid buildup.  Dandelion leaves are a natural diuretic. And they’ll also replace potassium your dog loses through excess urination. This isn’t true of pharmaceutical diuretics that deplete electrolytes in you dog. 

RELATED: Find out how else dandelion can help your dog … 

Hawthorn berries have a long tradition of helping with heart problems. It’s a powerful heart tonic that can help with CHF and other serious heart conditions. It can strengthen a weak or irregular heartbeat. It can dilate coronary vessels. Lastly, it may also improve your dog’s appetite and digestion.

Canine herbalist Rita Hogan recommends the following hawthorn protocol for heart murmurs. This protocol helpks balance the heart and won’t interfere with any. homeopathic remedies you may be using.

  1. Hawthorn tincture: 5 drops twice a day, in the mouth or in a small amount of food
  2. Hawthorn phytoembryonic therapy, 1:10 or 1:20 extraction: 3 drops twice daily, in the mouth or a small amount of food.
  3. Hawthorn flower essence: 4-6 drops twice daily, in the mouth or place in the water bowl.

RELATED: Learn how hawthorn supports your dog’s heart …

Omega-3 Fatty Acids
Omega-3 fatty acids like fish oil have long been known to promote overall cardiac health. They can lower heart disease risks and reduce chronic inflammation in the body. But instead of fish oil, which harms ocean environments and is often contaminated … choose a safe, sustainable omega-3 alternative like green lipped mussel oil

RELATED: Read more about the pros and cons of fish oil …

Coenzyme Q10 (CoQ10)
If there’s one must-have supplement for heart patients, CoQ10 is it. CoQ10 has so many benefits that support heart health. Countless studies report it can treat heart failure. Research even shows it reduces the risk of dying from heart disease complications. 


You should give your dog CoQ10 even if you’re using conventional drugs … in fact, especially if you’re using them. Several pharmaceutical drugs are known to deplete CoQ10 in the body.

CBD isn’t well known for helping with cardiac issues.  But it can have some remarkable results in managing heart disease symptoms. Holistic veterinarian Dr Edward Bassingthwaighte describes one CHF patient whose heart murmur was greatly improved with CBD. And CBD even helped the dog get off diuretics completely. One study in rats found CBD can reduce blood pressure and heart rate as well. 

RELATED: What you should know about CBD oil for dogs …

Diets high in antioxidants have been shown to reduce heart disease risk. Your dog’s body creates free radicals every day as part of his metabolic process. Free radicals also come from environmental toxins and other external sources. Free radicals can damage your dog’s cells and even his DNA. This process is called oxidation … and it’s linked to many chronic diseases, including heart disease. Antioxidants help control free radicals and protect the body from this damage. Include some antioxidant foods in your dog’s diet to boost his ability to fight heart disease. 

RELATED: Why your dog needs more antioxidants …

Garlic is a natural blood-thinner and vasodilator (expands blood vessels). So fresh garlic can support dogs with heart disease. 

Caution: Don’t use garlic if you’re using conventional drugs, as it doesn’t combine well with heart medications, especially blood pressure and blood thinning drugs

RELATED: How garlic can help your dog …

If your dog has dilated cardiomyopathy (DCM), make sure he’s getting enough taurine. Taurine deficiency can be a contributing factor in DCM. But you don’t have to give him taurine supplements (which are only available in synthetic form). Dogs can make their own taurine … their bodies just need the right food. Make sure he gets plenty of animal proteins in his diet. Feed a raw meat-based diet if you can, and include heart and other organ meats. 

RELATED: The role of taurine in DCM in dogs …

Eventually, your dog with serious heart disease may need pharmaceutical support. But you can stave off that moment by using some of these natural remedies. 


Etienne Côté et al. Management of incidentally detected heart murmurs in dogs and cats.Journal of Veterinary Cardiology, Volume 17, Issue 4, 2015, Pages 245-261, ISSN 1760-2734.

Caivano D, Dickson D, Martin M, Rishniw M. Murmur intensity in adult dogs with pulmonic and subaortic stenosis reflects disease severityJ Small Anim Pract. 2018 Mar;59(3):161-166. 

Rishniw M et al. Breed does not affect the association between murmur intensity and disease severity in dogs with pulmonic or subaortic stenosisJ Small Anim Pract. 2019 Aug;60(8):493-498. 

Pierre Serfass et al. Retrospective study of 942 small-sized dogs: Prevalence of left apical systolic heart murmur and left-sided heart failure, critical effects of breed and sex.Journal of Veterinary Cardiology, Volume 8, Issue 1, 2006, Pages 11-18, ISSN 1760-2734.

Jergler, Don. What You Need to Know About Murmurs and Heart Disease in Senior Dogs. Veterinary Practice News, 12 Aug. 2015.

DiNicolantonio JJ et al. Coenzyme Q10 for the treatment of heart failure: a review of the literature. Open Heart.2015 Oct 19;2(1):e000326. 

Leonardo BM et al.  5-HT1A receptors are involved in the cannabidiol-induced attenuation of behavioural and cardiovascular responses to acute restraint stress in ratsBritish Journal of Pharmacology, Vol 156, Jan 2009. 

Kaplan JL et al. Taurine deficiency and dilated cardiomyopathy in golden retrievers fed commercial diets. PLoS One. 2018 Dec 13;13(12):e0209112. 

Gaziano JM. Antioxidant vitamins and cardiovascular diseaseProc Assoc Am Physicians. 1999 Jan-Feb;111(1):2-9. 


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