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Heart Murmur in Dogs: What You Need to Know

A heart murmur is a common medical condition in dogs, and it is assessed that around 10% of all dogs have a heart murmur. A heart murmur is caused by rough blood flow within the heart, which creates an audible noise that can be heard as a whooshing or swishing sound when listening to the dog’s heart with a stethoscope. This sound can indicate a problem with the dog’s heart, but it does not always mean that the dog has a serious medical condition. In this article, we will explore heart murmurs in dogs, their causes, symptoms, diagnosis, and treatment options.

What Causes Heart Murmurs in Dogs?

There are several causes of dog heart murmurs.

Congenital Heart Defects

Some canines are born with heart defects that can cause heart murmurs. These flaws can include complications with the heart valves, such as mitral valve dysplasia, or irregularities in the structure of the heart, such as ventricular septal defects.

Age-Related Changes

As dogs get older, their heart muscles might weaken or the valves may thicken, which can lead to a heart murmur. This type of heart murmur known as degenerative valve disease is more typical in older dogs.


Dogs that have some bacterial infection like endocarditis, may experience cardiac murmurs. Endocarditis is an infection of the heart valves and can be caused by bacterial proliferation into the bloodstream through dental procedures, injuries, etc.


In some cases, tumors in the heart or blood vessels can cause heart murmurs in dogs. These tumors can be either benign or malignant.

Other Diseases

Other underlying conditions such as anemia, hyperthyroidism, or excessive blood pressure(hypertension) might potentially be the underlying cause of heart murmurs.

Breed Predisposition

Some breeds of dogs are more susceptible to developing heart murmurs. For example, Cavalier King Charles Spaniels are prone to mitral valve disease, while Boxers and Doberman Pinschers are more prone to aortic stenosis.

Types of Dog Heart Murmurs

There are different types of heart murmurs in dogs, each with its characteristics and possible underlying causes. Here are some of the common types of heart murmurs:

Innocent Heart Murmurs

Innocent heart murmurs do not indicate underlying heart disease or medical illness. They are often found in young dogs and puppies and are considered harmless. These murmurs are often quiet, systolic murmurs and do not need any treatment.

Systolic Heart Murmurs

The systole is the period when the heart pumps blood out of the heart chambers, and systolic heart murmurs happen when there is an issue with the heart’s contraction during systole. These murmurs which frequently sound whooshing or swishing can be caused by many underlying medical disorders, such as mitral valve disease, aortic stenosis, or dilated cardiomyopathy.

Diastolic Heart Murmurs

Diastolic heart murmurs arise during diastole, which is the stage when the heart chambers recline and fill with blood. These murmurs are often linked with problems in the heart valves, such as mitral valve regurgitation or tricuspid valve regurgitation. They usually produce a faint or low-pitched sound.

Continuous Heart Murmurs

Constant heart murmurs are audible during all the phases of the cardiac cycle, which means they are present during both systole and diastole. These murmurs are caused by a variety of issues, such as patent ductus arteriosus, and a congenital heart.

Certain breeds of dogs, such as Cavalier King Charles Spaniels, Boxers, and Doberman Pinschers, are also more prone to developing heart murmurs.

dog heart murmur in Terre Haute, IN

Stages of Heart Murmurs

Heart murmurs in dogs can be rated on a scale of 1 to 6 based on their strength and audibility. The grading system helps veterinarians assess the severity of the heart murmur and determine the appropriate course of action. Here are the stages or grades of heart murmurs in dogs:

Stage I

These murmurs are very soft and can only be heard with a stethoscope in a quiet room.

Stage II

These murmurs are a little louder than grade I murmurs and can be heard with a stethoscope in a quiet room. They might or could not be followed by other problems, and frequently not any medical attention is needed unless they persist or get worse.

Stage III

These murmurs are louder than grade II murmurs and can be detected without a stethoscope. They may be accompanied by other symptoms such as exercise intolerance or coughing, and further diagnostic tests may be necessary to determine the underlying cause.

Stage IV

These murmurs are loud and even in a vociferous environment, the stethoscope may pick up these murmurs. They may be accompanied by other symptoms such as difficulty breathing, exercise intolerance, or coughing, and further diagnostic tests are usually necessary to determine the underlying cause.

Stage V

A stethoscope held just slightly away from the chest wall will pick up these loud murmurs. Further diagnostic tests are required to identify the core issue since they are usually accompanied by additional symptoms such as weakness, exercise intolerance, or breathing difficulties.

Stage VI

These murmurs are very loud and can be heard with a stethoscope placed anywhere on the chest wall. They are usually accompanied by other symptoms such as collapse, severe weakness, or difficulty breathing, and emergency medical attention is necessary to stabilize the dog and determine the underlying cause.

Symptoms of Heart Murmurs in Dogs

Most dogs with heart murmurs do not show any outward symptoms, and the condition is usually detected during a routine physical examination. However, in some cases, dogs with heart murmurs may experience symptoms such as lethargy, weakness, coughing, difficulty breathing, and fainting. These symptoms can be caused by a variety of factors, including the severity of the heart murmur and the underlying cause of the condition.

Diagnosis of Heart Murmurs in Dogs

If your veterinarian suspects that your dog has a heart murmur, they will perform a physical examination, which will include listening to your dog’s heart with a stethoscope. If a cardiac murmur is detected, your veterinarian may recommend further testing, such as an electrocardiogram (ECG) or an echocardiogram. These tests can help to determine the severity of the heart murmur and identify any underlying medical conditions that may be causing the problem.

Treatment Options for Heart Murmurs in Dogs

The treatment options for heart murmurs in dogs depend on the underlying cause of the condition. In some cases, no treatment may be necessary, and the heart murmur may simply be monitored for any changes. However, if the heart murmur is caused by an underlying medical condition, such as heart disease or infection, treatment may be necessary. Treatment options may include medications, such as diuretics or ACE inhibitors, to help improve heart function and reduce the risk of complications.

Preventing Heart Murmurs in Dogs

While it is not always possible to prevent heart murmurs in dogs, there are some steps that pet owners can take to reduce the risk of their dogs developing this condition. These steps include:

Nutritional Management

Feeding your dog a healthy, balanced diet can help improve heart function and reduce the risk of heart disease. Avoiding foods high in salt and fat and feeding a diet rich in lean proteins, fruits, and vegetables can help improve heart health.

Weight Management

Maintaining a healthy weight is important for dogs with heart murmurs, as obesity can put extra strain on the heart. Regular exercise and portion control can help manage weight and improve overall heart health.

Stress Reduction

Reducing stress can help manage heart murmurs in dogs. Dogs with heart murmurs should be kept in a calm, quiet environment and should avoid stressful situations like loud noises, intense exercise, and other stressful activities.

Regular Check-Ups

Regular visits to the veterinarian can help monitor the progression of the heart murmur and any associated symptoms. Your vet may recommend diagnostic tests like X-rays, echocardiography, or electrocardiography to evaluate the heart’s function and any changes over time.

Supportive Care

For dogs with severe heart murmurs, supportive care may be necessary. This may include oxygen therapy, fluid therapy, and other treatments to manage symptoms and improve heart function.

It is important to note that non-medical treatments alone may not be sufficient for managing some heart murmurs, and medication or other medical interventions may be necessary.

Avoiding Exposure to Toxins

Toxins, such as tobacco smoke, can increase the risk of heart problems in dogs.


Heart murmurs are a common medical condition in dogs, and they can be caused by a variety of factors. While most dogs with heart murmurs do not show any visible symptoms, it is important to have your dog regularly examined by a veterinarian to identify any potential problems. If your dog does have a heart murmur, your veterinarian can help to determine the underlying cause of the condition.