What is a heart murmur?
- Heart murmurs are caused by turbulent blood flow, which creates abnormal sounds
- Murmurs can vary considerably in seriousness
- Most murmurs can be managed with appropriate monitoring and treatment
- Some dog breeds are more prone to heart issues than others including Cavalier King Charles Spaniels
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 Although the detection of a heart murmur in your dog sounds like scary news, they are a relatively common finding.
Murmurs in dogs vary considerably in the degree of severity though, so may suggest some tests to explore things further, as well as regular monitoring of your pet.
Heart murmurs are Common in:
Dogs of any age generally, including young puppies, but some breeds are more prone to heart murmurs than others including the Cavalier King Charles Spaniel, Great Danes, and Dobermann Pinschers.
What are the symptoms of heart murmurs in dogs?
Heart murmurs are caused by turbulent blood flow, which can be caused by issues like a faulty heart valve, obstructions in the heart, or changes in the viscosity (thickness) of the blood itself. This creates a heart murmurs sound of slight ‘whooshing’ sound in addition to the normal ‘lub dub’ sounds of the dog’s heart itself.
There are different levels of heart murmurs in dogs, from mild and quiet, to very loud and more serious murmurs.
Your vet will usually give the heart murmur a grade from 1 to 6 (1 being very quiet and barely audible and 6 being extremely loud with extra vibrations or a ‘thrill’ that can be felt). Further tests are still needed to determine the underlying cause of heart murmurs.
Some dogs will not show symptoms of a heart murmur (asymptomatic), with it only being detected at a routine booster vaccination examination, whereas other dogs may present to the vet in an extreme, collapsed state.
Many animals will display the following symptoms if their heart condition is affecting them –
- Lack of energy
- Reduced appetite
- Coughing
- Breathlessness
- Weight loss
- Weakness or fainting
- Pale gums, or even blue-tinged
- Fluid retention (causing breathing issues or a swollen abdomen)
Diagnosing a heart murmur in dogs
Most heart murmurs in dogs are first detected during an examination. As part of their physical exam, your vet will listen to your dog’s chest with a stethoscope.
If your vet hears a significant heart murmur, they may recommend further tests to try and work out what the underlying cause is.
The next steps may involve a blood test as a general health screen for your pet, but there are also tests available that look at specific markers released by the dog’s heart if it is under abnormal strain (NT-proBNP and troponin levels), such as with cardiac issues like heart disease or cardiac disease.
Diagnostic imaging is necessary to identify any secondary changes to the heart (such as muscle thickening or overall enlargement of the heart or any heart disease) as well as to identify the cause of the dog’s heart murmur.
This may involve anesthesia, which your vet will talk you through. X-rays are a good starting point as these will also identify fluid in the lungs, but an ultrasound scan, known as an echocardiogram, will look at the dog’s heart muscle and valves in more detail. This will then allow your vet to plan treatment for your pet.
Electrocardiograms (ECG) can be useful, particularly if your dog also has an irregular heart rhythm. This measures the electrical activity across the heart and gives clues as to what might be going wrong.
Sometimes a referral to a veterinary cardiologist or vet with expertise in ultrasounds is required to get a definitive diagnosis.
What causes heart murmurs in dogs?
There are a variety of different conditions that can cause a murmur in dogs. That is why further tests are useful, to not only plan treatment but also to give us a prognosis (i.e. is the condition serious and deteriorating, or can it be monitored for now?).
Here are some of the common conditions that can cause a heart murmur in dogs:
- Innocent flow murmurs – a quiet, innocent murmur detected in young puppies, which disappear as they mature
- Dilated cardiomyopathy – enlargement of the heart (dilated cardiomyopathy is more common in large and giant breeds)
- Mitral valve disease – issues with the valves that control the direction of blood flow (heart valve issues are more common in small breeds like Cavalier King Charles Spaniels)
- Anemia – reduction in red blood cells changing the viscosity of the blood
- Congenital problems – issues that a dog is born with such as major blood vessels that are narrowed or a hole in the heart, which can affect blood flow (Ventricular Septal Defect)
- Cancer – a tumor in the heart could cause blood flow disturbances
How are heart murmurs treated?
Treatment of heart murmurs will depend on the results of the tests that your vet performs. Some mild heart murmurs can be monitored, with repeat scans sometimes advised at regular intervals to check for any disease progression.
Other heart murmurs may be medically managed with a combination of daily medications recommended to help improve the function of the heart and reduce fluid accumulation in the body.
A change in diet can be helpful for some animals, as can careful exercise management, in the effort to treat heart murmurs.
Some dogs may require surgical intervention to improve their condition, particularly where there is a congenital issue such as a hole in the heart or narrowing of the major blood vessels (e.g. pulmonic stenosis).
Your vet will discuss the options with you and help guide your decisions to treat your pet’s heart murmur.
FAQ
Life expectancy with a heart murmur is very variable. Many dogs can survive into old age with a mild heart murmur, but more serious heart problems could shorten their life span. Following your vet’s advice regarding treatment and management of their condition is crucial to increase your pet’s chances of a longer survival time.
The degree of severity varies depending on the underlying cause of the heart murmur. Some mild murmurs may never cause an issue, whereas others can be very serious and debilitating. Your vet will be able to advise your further depending on your dog’s individual complaint.
Heart murmurs are not always fatal in dogs. Many have mild murmurs which may never cause a serious issue, whereas others can have a progressive illness that deteriorates over time. Seeking appropriate treatment for your pet can help improve quality of life as well as life expectancy.
Some dogs may show symptoms of their heart murmur such as a cough, breathlessness difficulty exercising, and weight loss. Other animals may be asymptomatic and not show any side effects from their murmur at all, or their symptoms could develop over time.
