Heart Murmur in Dogs: Should You Be Worried?

Heart Murmur in Dogs

The proper functioning of a dog’s heart is important to its health. There is no doubt as to what can happen if the heart that is central to all other functions goes bad.

Heart murmur is a fairly among common condition in dogs that is often seen and treated in the vet’s office.

In more severe cases it can be a distressing condition both to the dog and the dog’s owner; and the more you know about it the better you will be able to take care of your pet.

Heart murmur in dogs is not a disease in itself but it can suggest that the animal has an underlying problem that should be dealt with.

Heart murmur is really an abnormal sound that is heard when the doctor uses a stethoscope to listen to the heart of the dog.

This sound occurs when the heart’s walls or valves do not function properly to let blood in and out of the chambers of the heart.

The valve can malfunction when the blood enters or leaves the heart, or as it flows through the organ. The normal “Lubb Dupp”, “Lubb Dupp” rhythm of the heart that is heard when listening to it is added with a mild “pshh” or loud “whoosh” sound, a heart murmur.

Causes of Heart Murmurs

Congenital heart problems — In many cases, heart murmur is detected in puppies usually by the second vaccination. Two types of heart murmur usually evolve at this stage. One is usually a very soft murmur that is barely audible, and heard by the veterinary doctor. This is called an innocent “flow murmur” that goes away in about 4 – 5 months.


In the second case, the dog may be born with a congenital heart problem and a somewhat louder murmur will be heard. This will not disappear after months but will require the immediate attention of the doctor.

Although it has been detected at birth the condition can develop during later life (Summerfield, 2012).

Structural heart problems — The heart is divided into four chambers – two top chambers of the atria that receive blood from the veins in the body and two bottom ventricles that pump blood through arteries to the body. Each chamber of the heart is separated by a valve that controls the flow of blood, preventing it from flowing in the wrong direction.

One cause of heart murmur comes from the poor structure of the heart valves as seen in adult dogs. One or more of the valves that controls the flow of blood in and out of the heart may not function properly because:

  • there is a leak in the valve
  • there is thickening of the edges of the valve and so it cannot close or open properly
  • there is a hole in the valve

All of these problems disturb the flow of blood in the heart creating turbulence which is heard as a murmur. The incoming blood flow is disturbed due to abnormal valve or structures causing a vibration in the flow.

There is also disturbance in the flow of the blood through the heart due to an obstruction or in the outward flow where the vessels are diseased. There are disturbances that cause blood to back flow associated with a dysfunctional valve.

It can also be a result of patent ductus arteriosis or a disorder where there is an opening between two major blood vessels.

There could also be a defect in the septum, the walls that separate one chamber from the other in the heart.

Defects may be a result of diseases and inflammation that may exist in the heart such as endocarditis, which is an inflammation of the lining of the heart.

Endocarditis is caused by a germ that has travelled through the blood stream from an area of the body such as the mouth and has affected the lining of the valves.

Another heart disease called endocardiosis occurs quite regularly in dogs with heart disease. Endocardiosis occurs when the free edges of the valves of the heart thicken.

Blood flows through the heart in a forward movement. The valves in the heart exist to form a tight seal to prevent blood from leaking back into the chamber where it is coming from.

In endocardiosis the edges of the valves thicken therefore preventing them from closing properly and causing some blood to leak back into the chamber.

The dog’s heart now has to work harder to pump the required amount of blood for the body’s needs.

As the heart works harder to do its job, a heart murmur will be heard as the blood races through the chambers.

Dog heart x ray

Valvular stenosis or dysplasia is another source of heart murmur. Stenosis or dysplasia occurs when the size, shape or structure of a passage through which the blood flows becomes constricted or changes. The blood now has a narrower passage to go through and the heart works harder to push sufficient blood creating a whooshing murmur (PetWave.com, 2015).

Extra-Cardiac Problems

There could be some other problems existing in a dog’s system that may be affecting the flow of blood in the heart and causing what is termed a functional heart murmur.

A functional heart murmur can occur if the dog is anemic or where there is a low level of protein in the blood. Additionally, fever or infection, obesity, emaciation and even pregnancy can lead to heart murmur.

Make sure your dog stays active to avoid obesity, read our article on signs and solutions for overweight canines to learn more.

Take for example, an anemic case. There are not enough red blood cells present in the blood, causing it to be weak and watery.

As it passes through the heart valves it causes turbulence.  Heart murmurs have also been detected in young dogs that have infestations of parasites such as worm, fleas and ticks.

The parasites cause anemic conditions that affect how blood flows through the heart.

Grades of Heart Murmur

If you should listen to different dogs with heart murmur, you may hear different sound levels.

A murmur in one dog may be louder or softer than that in another. The level of the sound of the murmur reflects the amount of turbulence, or the intensity of the blood flow that is happening in the heart.

Heart murmur can be one of six grades depending on the sound level of the murmur.

Grades of heart murmur

Grade 1 – At this level the murmur can barely be heard.

Grade 2 — This is a rather soft sound but is easily heard with the stethoscope.

Heart murmur at grades 1 and 2 may only be heard intermittently and only on the side of the heart where the problem is.

At this stage it does not usually require any immediate medical attention especially if it occurs at puppy stage.

Your vet may however ask you to watch your dog for any further development which could be the appearance of a cough or lethargy which may indicate a worsening of an illness.

Grade 3 – At this stage the sound has medium loudness and is very distinct.

Grade 4 – The sound radiates to other parts of the chest area and can be heard anywhere that that you can hear the dog’s heart beating.

Dogs diagnosed at grades 3 and 4 mean a condition that requires more serious medical attention. Usually there is a persistent cough and the dog will become tired easily. Medication is needed to regulate the blood flow.

Grade 5 – The murmur is so loud, a stethoscope would pick up the sound even barely touching the chest. You can also feel the vibrations through the chest walls.

Grade 6 – The murmur has reached the peak of its loudness. The vibration can be felt without touching the walls of the chest with the stethoscope.

Grades 5 and 6 staging is an indication of something serious and may require surgery to correct the problem.

Symptoms of Heart Murmur

Heart Murmur in Dogs

As a dog owner you may not readily notice any clinical signs of heart murmur in your dog. The problem is usually only detected in a routine examination or a test for another medical problem. Heart murmur is usually a sign that your dog has an underlying heart condition. You may notice one or more of the following symptoms:

  • The dog develops a cough that is persistent owing to the build-up of fluid in the lungs.
  • Fluid retention causes distended abdomen.
  • There is weakness and lethargy
  • The dog collapses or has fainting spells.
  • He will not want to exercise and there is a reduction of normal activities.
  • He pants heavily even when at rest.
  • He is finding it difficult to breathe, especially when at rest.
  • His appetite will deteriorate and ultimately weight loss will set in.
  • He may show pale or a bluish tinge to the gums.

Dogs at Risk

Should you be concerned that your dog has or will develop a murmur? There are some breeds that seem to be prone to the more common heart defects that result in heart murmur.

The table below identifies some dogs that are at greater risks (Mercola.com, 2015).

Heart condition Breed
Acquired mitral valve disease Cavalier King Charles Spaniel, Dachshund, Small breeds
Congenital mitral valve disease Bull Terrier, Rottweiler
Patent ductus arteriosis Cocker and English Springer Spaniels, German Shepherd, Maltese, Poodle
Pulmonary stenosis Boxer, Cocker Spaniel, English Bulldog, Mastiff, Miniature Schnauzer, Samoyed, West Highland White Terrier
Sub-valvular aortic stenosis Boxer, German Shepherd, Golden Retriever, Newfoundland, Rottweiler
Congenital tricuspid valve disease Labrador Retriever
Ventricular septal defect English Springer Spaniel

Diagnosing the Problem


A dog owner will not identify heart murmur in his or her dog. There may be signs, however, that indicate that something is wrong with your pet. A heart murmur is most often discovered by the veterinarian surgeon during a routine examination or an examination for other medical problems.

The vet may detect through his stethoscope a heartbeat that is irregular in your dog. Further physical examination may indicate weak or abnormal pulses which could have underlying causes and recommend further tests, including:

  • An electrocardiogram (or ECG) – This is a simple non-invasive test in which the dog is hooked up to a machine and the electrical pulses emanating are recorded as the heart beats. To show how important this test can be, the tiny electrical pulses are amplified 3,000 times so that any abnormality in the heart will be picked up by the machine.
    Therefore, any disturbances in the heartbeat or the rhythm of the heart will be detected and the veterinarian will instantly know if there is a heart disease in your dog.
    To carry out an ECG, the animal is made to stand or lie down and electrodes are attached to the elbows and knees.
    For greater electrical conduction a gel is placed between the skin and the electrodes. There is no unpleasantness in the procedure to harm the dog and all that happens is that the machine records the electrical impulses. The vet will use the information to make further diagnosis.
  • An echocardiogram – This is simply an ultrasound done of the heart and helps to identify if something is wrong with the physical structure of the dog’s heart. Apart from determining the heart’s size, character of the tissues and the functioning of the muscles, an echocardiogram also allows the vet to evaluate the valves and also the blood flow into, through and out of the heart.
    The procedure for an echocardiogram is a bit more complicated than in the case of an electrocardiogram. The hair on the dog’s chest may need to be clipped so that the area over the heart is better exposed. The dog is placed on its side and held so that the exposed area is turned to the examiner. A conducting gel is placed on a probing device which is then moved across the area over the heart. The probe is also moved to under the ribs to ensure all angles of the heart are evaluated.
    Sound waves are transmitted from the probe to the heart and an image of the heart is recorded on a computer screen. Here the examiner is able to determine any abnormal conditions that may exist. In some cases an echocardiogram is done in conjunction with an electrocardiogram.
    A  Doppler examination is a specialized type of echocardiogram that measures the speed and direction of blood flow across the valves in the heart. This specific exam will help to locate the specific area that the turbulence is taking place and therefore identify the cause.
  • X-Ray – Radiographic images of the dog’s heart can provide important information about the dog’s heart health as it can show size, pulmonary veins and arteries structures and the condition of the valves.

Treatment Options for Heart Murmur

Can a heart murmur be treated any at all? A heart murmur is a just an abnormal sound in the heart caused by turbulence in blood flow. Very hardly will you even notice that a dog has a murmur.

You will have to have expert eyes or ears to detect any of this. Most often than not a murmur is the result of an underlying problem which may be in the heart itself or occurring outside of cardiac affairs.

If heart murmurs are diagnosed in puppies, a veterinary doctor will not usually prescribe treatment for them as the sound normally goes away in a few months or years.

Sometimes the body does take care of itself without any intervention. In many cases it will take a few years to determine if the murmur is a cause for concern and in many instances does not need to be treated.

Mitral valve disease in dogs

The heart valves are many times the offending parts causing heart murmurs. Defects in the mitral valve especially have come in for a good many of the causes of heart murmur.

The valve does not close properly likely because they have thickened and cannot be sealed to prevent blood from going back where it is coming from.

When problems like mitral valve defects occur, then the veterinary surgeon will definitely recommend surgery to repair or replace the valve.

A dog may develop a murmur due to the presence of heartworm. This is a parasite that is passed on by an infected mosquito.

The mosquito deposits the heartworm larvae into the bloodstream of the dog. After 6 – 7 months the larvae grow into mature worms that lodge themselves into the heart, lungs and other organs of the body.

Of course a dog that is infected with heartworm will exhibit signs of a defective heart and a heart murmur will indeed occur and be heard.

The doctor will prescribe medication that will rid the animal of the parasite and also repair any area that was affected. Our comprehensive tips on how to manage heartworms in dogs will be a great help to you, so check it out.

If a heart murmur is detected in your dog, the veterinary doctor will discuss with you how to manage your dog’s health to repair any damage from the underlying problem.

Omega 3 fatty acid for dogs

He may recommend some specialized diet, which could also mean changes in the sodium content that can be high in certain kibble foods.

Surgery will be recommended in cases of valvula stenosis and patent ductus arteriosis.

If you are into holistic or integrative medicine, you may take the advice of Dr. Karen Becker on Mercola.com (2015) to include various types of products in your dog’s diet.

The perennial Omega 3 fatty acids are not to be left out especially that found in the Krill fish. Recommended holistic remedies also include Chinese herbs, homeopathic remedies, amino acids supplements, and herbs such as Hawthorne Berry and Cayenne. Many have found our article on natural dog food a great help, so why not check it out?

Implications for Heart Murmur for Your Dog

From the very moment your vet advises that a murmur is coming from your dog, you will probably begin to consider the worse.

However, for most dogs that have a heart murmur there is no deteriorating heart health problems.

You should also know that heart murmur is not cured nor can it be corrected because it is not a cause but rather a result of some other issue. Read on our earlier article on congestive heart failure in dogs to give you more insight.

Heart murmur therefore does not affect the dog’s quality of life or how long it lives. The prognosis is therefore not for the murmur, but rather for the underlying condition that causes the murmur. The prognosis varies according to the severity of the issue that causes the murmur.

If the murmur is caused by a physiologic issue in the heart, there may be no need for treatment. Where the murmur is a case of something unrelated to the heart, if treatment is given for the condition, the murmur will eventually resolve itself.

Heart Murmur

The situation with congenital heart murmur is highly dependent on the type of defect that is present in the heart. The prognosis is extremely good especially if surgery can be used to correct the problem.

Where it is a deficiency in the mitral valve, medication can be applied to correct the problem. More extreme cases of cardiomyopathy will lead to heart failure and the outlook for such dogs is grave. The outlook for dogs with endocarditis will vary depending on how severe the infection is and how badly the effects on the heart valves. For this cause it is important that the dental care of the dog is given serious attention.

Your vet will discuss the condition of your dog after the tests have been done and the results are returned. He will also discuss the prognosis and suggest ways to treat and care for the dog.

In Conclusion

Heart murmur is a fairly common condition that occurs in dogs. A murmur indicates a disturbance in the regular blood flow in and through the heart. It can be frightening to learn that your dog has a murmur.

Fortunately, the condition itself is not a grave cause for concern. It however may mean the existence of a problem in the heart or externally in the dog’s body that needs attention.