My Pet Has a Heart Murmur — What Does It Actually Mean?
Hearing that your dog or cat has a heart murmur can be worrying. The word “murmur” can sound quite serious, but a heart murmur is actually a finding, rather than a diagnosis.
A murmur simply means that one of our vets can hear an extra or unusual sound when listening to your pet’s heart with a stethoscope. It is caused by blood flowing through the heart in a way that creates turbulence.
Sometimes a murmur is completely harmless. In other cases, it can be a sign of an underlying heart problem that needs further investigation.
So what does it actually mean for your pet?
What causes a heart murmur?
Normally, blood flows smoothly through the heart and major blood vessels. When that flow becomes more turbulent, it can create a noise that our vets can hear through a stethoscope.
There are several reasons why this can happen.
In some young animals, particularly puppies and kittens, a soft murmur can be “innocent” or physiological. This means there is no underlying heart disease and the murmur may disappear as they grow.
Murmurs can also occur because of a structural problem with the heart. For example, a valve may not be working properly, allowing blood to flow backwards, or there may be an abnormal connection between parts of the heart.
There are also conditions outside the heart that can cause a murmur. Anaemia, for example, can alter the way blood flows around the body and result in a murmur even when the heart itself is normal.
This is why hearing a murmur doesn’t immediately tell our vets exactly what is wrong.
Does the grade of the murmur tell us how serious it is?
You may hear our vets describe a murmur as a grade 1, 2, 3, 4, 5 or 6.
This grading system describes how easily the murmur can be heard with a stethoscope, with grade 1 being very quiet and grade 6 being very loud.
It is tempting to assume that a higher grade automatically means more serious heart disease, but it isn’t quite that simple.
The loudness of a murmur doesn’t necessarily tell us exactly what is happening inside the heart. A relatively quiet murmur can still be associated with significant disease, while a louder murmur isn’t automatically a sign that a pet is seriously unwell.
The important question is what is causing the murmur.
Why might our vets recommend more tests?
If one of our vets hears a murmur, they’ll consider your pet’s age, breed, medical history and examination findings alongside the murmur itself.
Sometimes, particularly with a very young and otherwise healthy animal, monitoring may be appropriate.
In other situations, further investigation can help us understand what is happening.
An echocardiogram, sometimes called a heart ultrasound, allows the heart to be examined while it is beating. It can show the heart chambers and valves, how well the heart is contracting and how blood is moving through it.
Depending on the individual pet, our vets may also recommend other investigations such as:
- Blood tests – these can look for conditions such as anaemia or other problems that could contribute to a murmur.
- Blood pressure measurement – high blood pressure can be associated with cardiovascular problems and is particularly relevant in some older cats.
- Chest X-rays – these can provide information about the size and shape of the heart and whether there are changes in the lungs.
- ECG – this records the electrical activity of the heart and can be useful if an abnormal heart rhythm is suspected.
Not every pet with a murmur needs every test. Our vets will recommend investigations based on what they find during the examination and what is appropriate for that individual animal.
But my pet seems completely normal…
This is one of the most important things to understand about heart disease.
Pets can have heart disease without appearing ill, particularly in the earlier stages.
They don’t always show obvious signs at home, which means a murmur can sometimes be picked up during a routine health check when an owner had no idea anything was wrong.
As heart disease progresses, however, you may notice changes such as:
- tiring more quickly on walks
- reluctance to exercise
- coughing
- breathing more quickly or heavily
- weakness or episodes of collapse
- reduced appetite
- weight loss
- a swollen abdomen in some cases
Cats can be particularly good at hiding signs of illness. Instead of obvious exercise intolerance, you might notice that your cat is sleeping more, playing less or simply behaving differently.
What can I monitor at home?
If your pet has been diagnosed with a heart condition, our vets may ask you to keep an eye on their breathing at home.
One useful thing to monitor is their resting or sleeping respiratory rate.
When your pet is asleep and not dreaming, count the number of breaths they take in one minute. Keeping a note of this can help our vets identify changes over time.
It is also worth paying attention to changes in exercise, appetite, behaviour and breathing.
If your pet suddenly develops difficulty breathing, collapses or appears severely unwell, this is an emergency and you should contact a veterinary practice straight away.
Does every heart murmur need treatment?
No.
A murmur itself isn’t something that necessarily needs treating. The important thing is identifying whether there is an underlying problem and, if there is, how significant it is.
Some murmurs are harmless and simply need monitoring. Other pets may have an underlying heart condition that requires medication or regular checks.
This is why our vets don’t make treatment decisions based on the murmur grade alone. We look at the whole picture — your pet’s age, breed, clinical signs, examination findings and, where appropriate, the results of further tests.
What happens if our vet finds a murmur?
Try not to panic.
Being told your pet has a heart murmur doesn’t automatically mean that they have heart failure or that something serious is about to happen.
For some pets, the murmur turns out to be an innocent finding. For others, further investigation allows us to identify heart disease early and put an appropriate monitoring or treatment plan in place.
At Milton Keynes Veterinary Group, our vets will talk through what they’ve heard, what it could mean for your particular pet and whether further investigation is recommended.
The most important thing to remember is that a heart murmur is a clue, not a diagnosis. The next step depends on what else we find when we look at your pet as a whole.