Heart Murmurs In Dogs

Ciara Zissman explains more about the different types of heart murmurs in dogs and how they are diagnosed.

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Every year at your dog’s annual vaccination our vets will also do a full health-check. It is at this time that occasionally a heart murmur may be identified. We may also find a heart murmur during a consultation if your dog is unwell.

What Is A Heart Murmur?

A heart murmur is an abnormal heart sound (a whooshing/swishing noise) heard between the two normal heart sounds. The normal heart sounds are heard due to the closure of the different heart valves. A heart murmur is caused by abnormal turbulent blood flow in the heart – this is usually due to some form of structural heart disease such as an abnormal heart valve, an abnormality in a major vessel or a hole between the heart chambers.

Types Of Heart Murmur

Some heart problems causing murmurs may be congenital, which means that the dog is born with the problem, whereas others are degenerative conditions that develop later in life. Sometimes a murmur can occur without heart disease, for example some dogs with anaemia (low red blood cell numbers) may have a heart murmur as the blood is thin which can lead to turbulence.

Puppies sometimes have a quiet murmur that we describe as ‘innocent’. In these cases the murmur is likely to resolve over a period of a few weeks to months and doesn’t reflect heart disease.

We use a grading system from 1-6 to describe the intensity of a heart murmur, with grade 1 being a very soft quiet murmur and grade 6 being a very loud murmur that can also be felt as vibration on the chest wall.

Diagnosing Heart Murmurs

When a vet hears a heart murmur it doesn’t always mean that your dog has significant heart disease. If it is a moderate to high grade then we will advise further investigation, to try to find out what is causing the heart murmur and whether treatment is needed. Initial investigations will depend on whether your dog is unwell at the time but will usually involve a blood sample, chest x-rays and echocardiography (an ultrasound scan of the heart). For some types of heart conditions in dogs it is beneficial for them to start treatment before they are showing any signs of being unwell with heart disease, so completing these investigations can be very important for your dog’s long-term health.

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