Heart Murmur In Dogs

Diagnosis Through Listening

Your veterinarian will diagnose your dog’s initial heart murmur through his stethoscope. To establish the cause of the murmur he may need to x-ray him and conduct a variety of other tests including blood tests, ultrasound or electrocardiogram. But the original murmur sound is found just using this simple piece of equipment in your usual examination room.

Vets have a scale of grading for heart murmurs, which if you ask them will give you an indication of the severity of the condition.

To do so they will always listen to your dog’s chest with a stethoscope, as well as doing a full examination.

The murmur grading system goes from Grade I, which is barely audible through their stethoscope, to Grade VI, which is very loud through the stephoscope and produced vibrations that can be felt by putting your hands on the dog’s chest.

Your vet may also refer to ‘plateau’ murmur sounds, which simply means that the vibration is consistent. They may also say it ‘crescendos and decrescendos’ or ‘decrescendos’. This differentiates between murmurs which start soft, great more apparent and then fade again, and those which start loudly and become softer.

They will also note the location of the heart murmur.

These descriptions should not be a cause for alarm to you, they are simply a way of your vet beginning to establish what might be causing the murmur to happen.

Some heart murmurs are associated with diseases and may resolve when the disease is treated. Some are associated with disorders of the heart itself. Others are associated with immaturity of the circulatory system and may resolve as the puppy grows up.

Heart Murmur in Puppies

Most of you will have visited your vet soon after collecting your new Labrador puppy. It is very common for new puppy owners to be told that their puppy has a heart murmur. And a puppy heart murmur sounds scary, in most cases it is nothing to worry about.

These are simply as a result of the puppy having a developing circulatory system pumping his blood around his body.

Should I worry?

Heart murmurs in puppies are not at all uncommon.  And many fall into the bracket of ‘immature hearts’ and will resolve in time. We usually call these ‘innocent’ murmurs and many puppies have them, especially in the larger breeds.

It can still be a worry to be told that your puppy has a heart murmur, and you are bound to be concerned. But in all probability he will be just fine.

Ask your vet if he thinks the murmur is innocent. 

If he does, then you’ll just need to pop back with the puppy for a check up in a few weeks. Innocent heart murmurs usually disappear by the time your pup is 4 or 5 months old.

Your vet probably won’t be able to hear the murmur any more at the next exam or the one after.

However, sometimes a puppy’s heart murmur can be indicative of a problem with their heart. This can also be the case with adult Labradors too.  So let’s have a look at some common Labrador health issues which could cause a heart murmur.

Potential Causes of a Heart Murmur in Dogs

There are a huge range of conditions that can cause a heart murmur in dogs. If your dog has a heart murmur, this is not in itself his ‘condition’. Rather the heart murmur is a symptom of another condition that your dog is suffering from.

This other condition is causing the blood flow in the heart to be disturbed, either because it is changing the blood flow through the valves or because it has damaged the valves or heart chambers themselves.

These disturbances in blood flow can be caused by a lot of different conditions, but some of the most common ones are

• Anaemia – Low level of red blood cells
• Aortic stenosis – A narrowing of the valves, causing the heart to have to pump harder
• Cardiomyopathy – Disease causing the weakening of the muscle of the heart’s ventricles
• Conjestive heart failure – usually accompanied by a cough, shortness of breath and lethargy
• Fever – having a raised temperature can temporarily cause a heart murmur to be found
• Heartworm – a parasitic roundworm
• Hyperthyroidism – an over active thyroid
• Hypoproteinemia – Low level of protein in the blood
• Infection
• Mitral valve prolapse – the heart valve is not closing properly and allowing blood to flow the wrong way
• Pregnancy – Short term stress put on the heart causing the irregularity
• Pulmonic stenosis – A narrowing of the valves, causing the heart to have to pump harder
• Tricuspid reguritation – the heart valve is not closing properly and allowing blood to flow the wrong way
• Ventricular septal defect – a hole in the wall that seperates the left and right ventricles of the heart

As you can see, there are quite a range of possibilities, but most of them come down to problems with the heart itself or the blood flowing through it.

Treatment Options

The treatment your dog will receive will depend upon the cause of his heart murmur. Some heart murmurs require no treatment at all, as they are not actually doing them any harm.

In these cases the vet will simply want you to bring your dog in for regular checkups to make sure that the situation is not changing.

If your puppy continues to have a heart murmur, or your older dog is diagnosed with one that has an underlying cause that could impact their health, you will need to follow your veterinarians advise regarding medication and ongoing treatment depending upon the cause.

If your vet gives you a diagnosis, I recommend reading up as much about that specific cause as possible.

Don’t be afraid to ask your veterinarian lots of questions, and if you are concerned then remember it is always okay to politely seek a second opinion elsewhere.

But remember, your vet wants to see your dog stay healthy. Follow his advice and recommendations for care, and hopefully he will stay fit and well for many years to come.