In this blog post we’ll discuss what a heart murmur is, some common conditions which could result in a canine heart murmur, what a dog heart murmur could progress to, and what the prognosis could be.
What exactly is a heart murmur
It is an unusual sound heard whilst listening to the heart with a stethoscope. Where it can be heard can depend on the issue. This sound is caused by rough or turbulent blood flow within the heart, and the sound can vary in intensity depending on how turbulent the flow is. This turbulent flow can be caused by an issue with one or more valves in the heart, or a hole between chambers in the heart.
How do vets grade a dog heart murmur
They are often graded in intensity out of VI (six). So, for example a grade I/VI is very soft or can barely be heard. In contrast, a grade VI/VI is extremely loud, and the turbulence can sometime be felt by placing your fingers on the dog’s chest where the heart is. It is important to know that how loud the murmur is doesn’t always correspond to how serious the problem is. Specifics of when the murmur is heard in relation to the heart beat can give vets further information on what could potentially be the cause and how serious it could be.
Can young dogs be born with heart murmurs
Commonly, some young puppies can have very faint heart murmurs, often called ‘innocent’ heart murmurs as they are not a cause for concern. They can be heard whilst the puppy is growing quickly, and often disappear before 6 months old.
However, uncommonly, some puppies can be born with a structural issue with their heart. Your vet can often know if something is wrong depending on the heart murmur they can hear, and signs that the puppy may be showing. Additional tests such as an electrocardiogram (ECG) and/or heart scan (echocardiography) may need to be carried out to find out exactly what is wrong. There are quite a few different heart conditions which could affect puppies. The conditions vary from narrowing of the heart valve openings (stenosis), to holes between the chambers of the heart (septal defects). Your vet would be able to discuss further if they suspect there could be an issue.
Mitral valve disease
This is the most common heart disease affecting the heart valves, causing a dog heart murmur. It affects mainly small to medium breed older dogs, but can be seen in large breed dogs too. The mitral valve separates the two chambers (atrium and ventricle) on the left side of the heart. Degenerative changes in the valve prevent it from closing effectively, resulting in blood leaking backwards through the valve, causing turbulence and a heart murmur. As all the blood that should be getting pushed forwards is not getting there, the heart tries to compensate by growing larger in size. Eventually the heart can no longer compensate and fails, causing left sided congestive heart failure.
Unfortunately, mitral valve disease is an irreversible condition, meaning there is no cure. However, medications can often help slow down the progression of it, allowing the affected dog to live a more comfortable life for longer.
Dilated Cardiomyopathy
This disease affects the heart muscle by causing the muscle to deteriorate and become thinner. When the muscle reduces, the heart is no longer able to effectively pump blood like it used to, causing congestive heart failure.
What is congestive heart failure
It is when the heart is no longer able to pump enough blood to meet the demands of the body.
Left sided failure occurs when the blood leaks back through the mitral valve and causes build-up of blood in the lung blood vessels. This results in fluid leaking into the lungs (pulmonary oedema).
Right sided failure occurs when blood builds up in the blood vessels of the rest of the body, causing fluid to leak out of the vessels and into body cavities such as the abdomen (belly).
Signs of congestive heart failure
- Coughing or struggling to breath
- Weakness (especially in the back legs), and eventually collapse
- Unable to exercise as much and getting tired very quickly
- Swelling within the abdomen.
Medications can help ease the signs of heart failure for a certain period.
Prognosis of a dog heart murmur
The prognosis (or the outcome of the condition) can vary hugely, depending on the disease and the stage that it is at when discovered. For example, if a surgery can be carried out to a condition which a young dog has, then they may go on to live a full and normal life. The prognosis for conditions of older dogs varies, depending on whether it can be managed with long term medications. However, if the dog is showing some of the signs of heart failure mentioned above, the prognosis is poor even with medications, as the condition will have progressed too far already.
In summary, dog heart murmurs, the conditions causing them, and their severity can vary hugely. If your vet detects a dog heart murmur, depending on the type of dog and age, there could be different possible causes of it. Detecting it early is key to increasing the dog’s lifespan. If your dog is showing any of the signs mentioned above, ensure they see a vet ASAP.
Note:The advice provided in this blog post is intended for informational purposes and does not constitute veterinary advice. If in doubt always seek veterinary advice.