Our veterinarians have answered the most common questions about a heart murmur in dogs.
Disclaimer: All content and information on this website are for informational and educational purposes only and do not constitute veterinary medical or pet health care advice.
What is a heart murmur?
A heart murmur is an additional abnormal heart sound. Your veterinarian can hear it while listening to your pet’s heart with a stethoscope.
A murmur is created by a turbulent blood flow inside the heart or in major nearby vessels.
Is a heart murmur in dogs dangerous?
A dog heart murmur is not a disease by itself. So, to answer the question of whether a dog heart murmur is serious, we need to know what is causing it.
Depending on the cause, a murmur can be harmless and not affect the dog, be a sign of severe disease, or anything in between.
What causes a heart murmur in dogs?
There are many causes of heart murmurs. In short, murmurs can be
- innocent with no apparent cause and making no harm,
- physiologic with no heart pathology involved, and
- pathologic due to a heart or large vessel issue.
Innocent murmurs or “puppy murmurs”
These murmurs are quiet and have no identifiable cause.
Veterinarians frequently hear innocent murmurs in puppies during their first exam and vaccination. Such murmurs do not worsen with time and disappear by 5 months of age. There are also no signs of disease present.
Remember, not all murmurs in puppies are innocent! Some can be a sign of disease even if no symptoms are present. In this case, a murmur can require immediate attention, diagnostics, and treatment, while innocent murmurs are usually only monitored.
Physiologic heart murmurs
Unlike innocent murmurs, these have an identifiable cause. However, that cause is not a heart disease.
Physiologic murmurs can occur for many reasons, including anemia (low red blood cell count), low blood protein, high blood pressure, fever, and pregnancy.
Pathologic heart murmurs
This type of murmur is related to a problem in the heart or nearby vessels.
Possible causes of a pathologic murmur in dogs are leaking or too narrow valves or abnormal connections between heart chambers or major vessels.
Despite being named pathologic, these murmurs are not always serious or dangerous. Sometimes, they signify very mild heart pathology that does not require anything but occasional check-ups at the vet. The opposite can be true, too.
Can anxiety cause a heart murmur in dogs?
It is possible that a veterinarian can hear a heart murmur in a very excited or extremely stressed dog due to the heart pumping very fast and with increased strength.
In such circumstances, it is also generally very hard to listen to the dog’s heart and distinguish between normal heart sounds, heart murmurs, and breathing or rubbing noises.
It is best to repeat listening to the heart in a calmer dog later.
What are the symptoms of a heart murmur in dogs?
In most cases, there are no obvious dog heart murmur symptoms. Instead, symptoms of the underlying cause of the murmur can be present.
In the case of heart disease-related murmurs, those signs can be:
- cough
- increased breathing rate and shortness of breath
- bluish tinge to the gums
- fluid in the belly
- fatigue, fainting, collapse,
and many others in different combinations depending on the exact cause.
Even with heart-related murmurs, in many cases, no symptoms are evident for years or at all. That happens quite a lot in dogs with myxomatous mitral valve disease and with some congenital heart defects.
Also, it is essential to understand that signs your dog might have are not always related to the murmur even when they are present simultaneously.
Your veterinarian will likely try to determine the cause of the murmur to see if it is a cause of your pet’s symptoms.
Can you feel a dog’s heart murmur?
Usually, you cannot feel the murmur unless it is a murmur of one of the highest grades (5 out of 6 or 6 out of 6; please refer to Dog heart murmur grades for details). Then, it will be possible to feel a vibration or so-called precordial thrill with your hand touching a dog’s chest at the place where the heart is.
Dog heart murmur grades (stages, levels)
Veterinarians commonly grade murmurs using a scale from 1 to 6.
Grade 1 is the quietest, and 6 is the loudest. In your dog’s medical history, it will probably be written as I/VI or 1/6 (which means grade 1 out of 6), II/VI or 2/6 and so on.
- Grade 1 murmur in dogs is very quiet. Your veterinarian will need a quiet room and a quiet dog to hear it. It is frequently heard only over a particular area of the heart and can be easily missed.
- Grade 2 heart murmur is still quiet but readily heard.
- Grade 3 heart murmur is of moderate intensity, and your veterinarian will easily hear it.
- Grade 4 heart murmur in dogs is loud and easily heard over the area where it originates and in other areas where it radiates.
- Grade 5 murmur is very loud, and you can feel it with your hand touching the heart area.
- Grade 6 murmur is so loud that it can be heard even when your veterinarian moves their stethoscope from the chest. You can also feel it with your hand.
Sometimes, grades of a heart murmur in dogs are described as grade 2-3, grade 3-4, or similar when it is hard to decide on the exact grade. At other times, veterinarians can use words like mild, moderate, or severe heart murmur.
How bad is the grade of my dog’s murmur?
It might be hard to comprehend, but the loudness of a murmur does not always correspond with the disease severity and prognosis.
So, ask your veterinarian how serious a specific grade of murmur in your pet is. Their answer will be based on the exact cause of the murmur and many other parameters and tests, frequently including ultrasound measurements.
How to treat a heart murmur in dogs?
The short answer is that veterinarians do not treat heart murmur itself.
There are no medications, natural remedies, or diet for a dog’s heart murmur per se.
Treatment for a heart murmur in dogs is not for a murmur but rather for the disease that causes it.
In some cases, dogs with a murmur never require any treatment.
In other cases, they might not require treatment now, but as the disease progresses, they might potentially need medicines prescribed in the future.
Still, some dogs with murmurs require urgent treatment, be it medical or surgical, due to their heart condition.
Unfortunately, some diseases that cause murmurs might not have a good prognosis even with correct and timely treatment.
Can a dog with a heart murmur exercise?
Again, it all depends on the underlying diagnosis.
A puppy with an innocent murmur can usually exercise as much as they want. In contrast, a dog with a murmur and congestive heart failure must have their exercise restricted to a certain point, per your veterinarian’s advice.
If you have a sport or working dog, we recommend you talk to your veterinarian to discuss how much work your dog can safely do, if any.
Can a dog with a heart murmur go under anesthesia?
Dogs with heart murmurs commonly undergo anesthesia for many different reasons – from spays and neuters to dental cleanings to urgent surgical procedures.
Ask your veterinarian about any risks related to the murmur or your pet’s heart condition before scheduling any procedures under anesthesia.
Your veterinarian may recommend additional testing or a cardiologist exam before anesthesia. This will help to evaluate the current situation and potential risks.
In some cases, your veterinarian can recommend undergoing anesthesia at a specialty veterinary hospital that has experienced anesthesiologists working daily with sick patients with a higher risk of anesthetic complications.
Can a dog with a heart murmur undergo dental cleaning?
Dental cleaning can be safely done in many dogs with heart murmurs.
General anesthesia is required for proper teeth cleaning – ultrasonic scaling and polishing all surfaces, including hard-to-reach ones and those under the gum lines.
So, the main question here is whether a dog with a heart murmur can undergo anesthesia for a dental cleaning. Please refer to the answer to this question above.
What is the life expectancy of a dog with a murmur?
As with symptoms and treatment, the life expectancy of dogs with heart murmurs can drastically differ. It depends on the cause of the heart murmur.
Some dogs with heart murmurs can have normal lifespans. In others, the disease related to the murmur can lead to death in days, months, or years.
Ask your veterinarian who knows your pet and their medical history for the prognosis. Also, ask what you can do in terms of medical and home care to prolong your pet’s life and increase its quality.
References
Mark Rishniw. Heart murmurs in dogs and cats. Last accessed on March 2nd, 2024.
Tilley L. and colleagues. Manual of canine and feline cardiology. Fourth edition.