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Heart Murmurs in Dogs

Reviewed by Dr Arianne Fabella, Boarded in Cardiology

What is a Heart Murmur in Dogs?

Heart murmurs in dogs are abnormal sounds heard before, after or during the normal heart sounds. Typically, they result from turbulent blood flow within the heart or blood vessels. When a veterinarian listens to a dog’s heart with a stethoscope, they may detect these murmurs, which can vary in intensity and pitch. It’s essential to understand that not all heart murmurs indicate a severe health issue, but they should always be evaluated by a veterinary professional to determine their cause and potential impact on the dog’s health.

What are the Symptoms of Heart Murmurs in Dogs?

Identifying the symptoms related to heart murmurs in dogs can be challenging because they often don’t show any signs until the condition has progressed. However, some common symptoms to watch for include:

  • Lethargy and exercise intolerance: Dogs may appear more tired than usual, lacking energy during walks or playtime.
  • Difficulty breathing: Laboured breathing or shortness of breath, especially at rest
  • Persistent coughing: Particularly at night or after exercise and often with laboured breathing.
  • Reduced appetite and weight loss: Lost interest in food or experience unexplained weight loss.
  • Fainting or collapsing: In severe cases, dogs may faint or collapse due to inadequate blood flow

How is a Heart Murmur in Dogs Found?

A heart murmur is often heard on a veterinarian’s physical examination and in louder murmurs it can be felt on the outside of the chest. Diagnostic tests to find out where the murmur may be coming from may include the following.

Echocardiogram (heart ultrasound)

This non-invasive imaging test provides detailed images of the heart’s structure and function, allowing cardiologists to assess the consequences of the murmur and identify any underlying heart conditions.


Chest X-rays can reveal abnormalities in the heart’s size and shape, as well as any fluid buildup in the lungs.

Electrocardiogram (ECG or EKG)

This test measures the electrical activity of the heart and can help diagnose arrhythmias or abnormal heart rhythms associated with heart murmurs. This can be performed in appointments with portable units or if longer periods of time are needed, they can be measured with a “holter monitor” which is a small ECG machine the dog wears home.

Blood Tests

Blood work can assess organ function should medications be needed to treat the heart murmur and check for conditions that can cause murmurs such as heartworm disease.

What Causes Heart Murmurs in Dogs?

Heart murmurs in dogs can have various causes, including:

  • Congenital Heart Defects: Some dogs are born with structural abnormalities in their hearts, such as defective valves or holes between chambers, leading to turbulent blood flow and murmurs.
  • Valvular Disease: Degenerative changes in the heart valves, such as thickening or weakening, can result in leaky valves, allowing blood to flow backward and causing murmurs.
  • Endocarditis: Bacterial infections of the heart valves can cause inflammation and damage, leading to murmurs and potentially life-threatening complications.
  • Dilated Cardiomyopathy (DCM): This condition involves the enlargement and weakening of the heart muscle, impairing its ability to pump blood effectively and causing murmurs.
  • Heartworm Disease: Infestation with heartworms can lead to inflammation and damage to the heart and blood vessels. When the infection is severe it can result in murmurs when the worms obstruct the valves.

How to Treat Conditions that Cause Heart Murmurs in Dogs

Treatment for heart murmurs in dogs depends on the underlying cause and severity of the condition. In many cases, management focuses on:

  • Medication: Prescription medications can be prescribed by a cardiologist or your veterinarian to reduce fluid build-up, dilate blood vessels, or regulate heart rate and rhythm
  • Regular Monitoring: Dogs with heart murmurs require regular check-ups and diagnostic tests to monitor their condition, adjust treatment as needed, and detect any complications early.
  • Minimally-invasive Surgical Intervention: In some cases, a procedure may be necessary to repair damaged heart valves, correct congenital defects, or remove heartworms.

Surgery at SASH to treat heart murmur in dogs

SASH is one of the few veterinary hospitals in NSW to offer a broad range of cardiac treatment options performed by qualified veterinary cardiologists. Common surgical treatments for heart murmurs involve a minimally invasive surgical procedures broadly known as cardiac catheterisation or intervention. For these procedures, a tiny (<1 cm) incision is made to insert a device or balloon which corrects or improves the underlying condition.

If a surgical procedure is required, SASH North Ryde is the only place in NSW where a team of Cardiologists are able to work with a number of other specialists to provide the best possible patient outcome for cardiac cases. Collaboration at SASH often involves the unique combination of:

  • Specialist Anaesthetists – to provide safer anaesthetic plans, especially important for patients with heart conditions
  • Surgical Specialists – to assist with complex cardiac surgeries
  • Critical Care Specialists – to provide patient care in the ICU for those that require intensive monitoring after a procedure

While heart murmurs in dogs can be concerning, prompt and accurate diagnosis, together with appropriate treatment can help improve the quality and length of life for affected pets. Pet owners should remain vigilant for any signs of heart murmurs and seek prompt veterinary care if they suspect a problem. With the right treatment and care, many dogs with heart murmurs can lead happy, active lives.

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