By Courtney Prue | May 8, 2025

Symptoms Of Heart Murmur In Dogs

What is a heart murmur?

A heart murmur is an abnormal sound heard when listening to a dog’s heart with a stethoscope. Normally, a dog’s heart produces two distinct sounds, described as “lub” and “dub.” A heart murmur is an extra sound that can be heard between the two sounds, creating a “shooshing” or “whooshing” sound. This sound indicates turbulent blood flow through the heart. This turbulence can be created by any change to the normal smooth movement of blood through the heart. This includes narrowing, expansion, obstructions, other structural changes, and changes to the consistency of the blood.

A heart murmur’s grade, ranging from 1 to 6, describes the loudness of the murmur. A grade 1 heart murmur is soft, while a grade 6 heart murmur is loud and palpable. In dogs, higher grades usually indicate more significant heart disease.

What is heart disease in dogs? 

Heart disease refers to any condition that affects the heart’s ability to function properly. There are several different types of heart disease that can affect dogs, including:

• Congenital heart disease: This is a heart defect that a dog is born with.
• Valvular heart disease: This is a condition in which the valves in the heart do not function properly, leading to blood flow problems.
• Cardiomyopathy: This is a disease of the heart muscle itself, which can cause it to become weak or enlarged.
• Heartworm disease: This is a condition caused by a parasitic worm that lives in the heart and pulmonary arteries.

What types of heart disease can dogs get? 

There are several types of heart disease that can affect dogs, each with its own set of causes, symptoms, and treatment options. Some of the most common types of heart disease in dogs include:

• Mitral Valve Disease (MMVD): This is a type of heart disease that affects the mitral valve, which is responsible for controlling blood flow between the left atrium and ventricle. In MMVD, the valve thickens and doesn’t close properly, allowing blood to flow backwards in the wrong direction. This type of heart disease accounts for approximately 75% of all canine heart disease cases. 
• Dilated Cardiomyopathy (DCM): This is a type of heart disease that affects the heart muscle, causing it to become thin and weakened. As a result, the heart cannot pump blood effectively, leading to heart failure. This type of heart disease is most commonly seen in large and giant breeds, such as Great Danes, Boxers, and Doberman Pinschers.
• Pulmonary Stenosis: This is a type of heart disease that affects the pulmonary valve, which controls blood flow between the right ventricle and the pulmonary artery. In pulmonary stenosis, the valve becomes narrowed, making it harder for blood to flow through it. 
• Aortic Stenosis: This is a type of heart disease that affects the aortic valve, which controls blood flow between the left ventricle and the aorta. In aortic stenosis, the valve becomes narrowed, making it harder for blood to flow through it. 

What are the common causes of heart disease in dogs? 

There are several factors that can contribute to the development of heart disease in dogs, including:

• Age: Older dogs are more likely to develop heart disease.
• Breed: Certain breeds are more prone to heart disease than others, such as Cavalier King Charles Spaniels and Doberman Pinschers.
• Genetics: Some forms of heart disease are hereditary.
• Diet: A poor diet can contribute to heart disease in dogs.
• Infection: Some infections, such as heartworm disease, can lead to heart disease.

How do I know if my dog has a heart disease? 

The symptoms of heart murmur in dogs and heart disease can vary depending on the type and severity of the condition. Some common symptoms of heart disease include:

• Coughing, especially at night or after exercise
• Difficulty breathing
• Rapid breathing or panting
• Fatigue or weakness
• Fainting or collapsing
• Loss of appetite or weight loss
• Swelling in the abdomen or limbs

Can a heart murmur in a dog cause sudden death?

In some cases, heart disease in dogs can lead to an emergency, especially when their lungs are impacted. If you suspect your dog is in distress, it’s crucial to act quickly and seek veterinary care immediately.

• Ongoing difficulty breathing or shortness of breath
• Rapid breathing or panting that doesn’t settle even when at rest 
• Blue or grey gums and tongue
• Collapse or loss of consciousness

If you observe any of these symptoms of heart murmur in dogs or heart disease, seeking immediate veterinary attention is important. Time is critical in emergency situations, and a delay in treatment can have serious consequences for your dog’s health. Don’t hesitate to call your veterinarian, our team or an emergency veterinary clinic for guidance on how to proceed.

How is a heart disease diagnosed? 

Once a heart murmur has been detected by your veterinarian, further diagnostics can help identify the cause, indicate the severity, track disease progress and treatment efficacy and more.

• X-rays: These can show the size and shape of the heart and can detect fluid buildup in the lungs.
• Electrocardiogram (ECG): This measures the electrical activity of the heart and can detect abnormal rhythms.
• Echocardiogram: This is an ultrasound of the heart that can show how well the heart is functioning and detect any abnormalities.
• Blood tests: These can help detect any underlying health conditions that may be contributing to heart disease.

Can a heart disease be treated?

The treatment of heart disease in dogs will depend on the type and severity of the condition. Some common treatments include:

• Medications: There are several medications that can help manage heart disease in dogs, including:
  • Pimobendan which increases heart muscle strength and improves blood flow
  • Diuretics to reduce fluid buildup
  • ACE inhibitors to help dilate blood vessels
  • Beta-blockers to slow the heart rate.
• Dietary changes: A diet that is low in sodium and high in protein can help manage heart disease in dogs.
• Exercise restriction: In some cases, it may be necessary to restrict your dog’s exercise to prevent overexertion.
• Surgery: In some cases, surgery may be necessary to repair or replace damaged heart valves or to remove heart tumours. These are specialist surgeries and will involve referrals. 

The medical management of heart disease can be confusing and overwhelming. Get in touch with our team today for a personalised discussion. 

How do I manage my dog’s heart disease at home?

Here are some tips to help you optimise your dog’s care at home:

• Monitor your dog’s breathing: This includes the effort used, as well as the rate. An important factor to monitor is their resting respiratory rate. While deeply asleep, count the number of breaths taken in 1 minute (or in 15 seconds and then multiply by 4). The rate should be between 10-20. If it is over 30 breaths per minute, ring the vet ASAP as this indicates possible congestive heart failure.
• Create a comfortable living space: Ensure your dog’s living space is warm, quiet, and comfortable. 
• Manage stress: Stress can worsen your cat’s heart disease. Try to minimise stress by keeping their routine consistent, minimising loud noises, and providing a calm environment.
• Reduce excitement and manage stress: Stress and high-energy activities can put extra stress on the heart and lungs. Provide low-energy exercise and play, keep their routine consistent, minimise loud noises, and provide a calm environment.
• Regular check-ups: Your vet will monitor your pets condition and make changes to their treatment plan as necessary.
• Consider palliative care to maximise comfort for as long as possible.

An in-home veterinary assessment can also be helpful to identify any other areas of improvement that can help your beloved pet stay comfortable for as long as possible. 

End-of-life care tips

If your dog’s heart disease has progressed to a point where treatment is no longer effective or its symptoms are too severe, it’s important to consider end-of-life care options, including possibly putting your dog to sleep (euthanasia). This can be an overwhelming and distressing thing to even think about. Rest Your Paws is here to support you and provide compassionate care for your beloved pet throughout their journey.

Here are some end-of-life care tips for dogs with heart disease:

• Keep them hydrated and well-nourished with some delicious food
• Spend quality time with them, making the most of every moment, such as with a bucket list.
• Offer a calm and peaceful environment, free from stressors that can exacerbate symptoms of heart murmur in dogs and heart disease
• Administer medications as prescribed for pain management and symptom relief. Your veterinarian may increase doses of medications such as diuretics to reduce fluid accumulation.
• Closely monitor their breathing rate and effort as described above.
• Evaluate their quality of life regularly, or reach out to a palliative care vet to help you with this. 
• Consult our End of Life Care Pack to get prepared to put your dog to sleep.
• Track good days and bad days on our Quality of Life Assessment Calendar.

We understand that facing a diagnosis of heart disease in your beloved dog can be a difficult and emotional time. However, with early detection, proper treatment, and careful management, your dog can continue to enjoy a happy and fulfilling life. Remember to work closely with your veterinarian to develop a comprehensive care plan that meets your dog’s individual needs. As your dog’s caretaker, it’s important to stay positive and provide plenty of love and support throughout the journey. Cherish the time you have with your furry companion and make every moment count. Rest assured that Rest Your Paws is here to support you and your furry friend every step of the way. Please do not hesitate to reach out to us if you have any questions or concerns – we are here to help.

Rest Your Paws

We offer in-home pet euthanasia for dogs and cats. Say goodbye with peace and dignity to your beloved pet. Professional and experienced end-of-life support.