Heart Murmur In Large Breed Dogs

Any dog can get a heart murmur and large breed dogs are no exception to this unfortunate fact.

Even though heart murmurs sound extremely serious, they aren’t always. While some heart murmurs in large breed dogs can be extremely dangerous, others are classified as innocent (meaning simply a noise that can occur as blood passes through a normal heart) and aren’t dangerous at all.

What Exactly Is a Heart Murmur?

A heart murmur is an abnormal heart sound, Veterinarians will usually detect a heart murmur by using a stethoscope to listen to the heart. Some severe heart murmurs can be felt when you lay your hands on a dog’s chest.

What are the Causes of Heart Murmurs?

There are several types of heart murmurs and they are all caused by the blood flow in the heart being turbulent.

These disturbances can be broken down into three categories.

  1. Problems that are caused by abnormal vibrations or valves
  2. Problems that are caused by dilated vessels, diseased valves, or obstruction
  3. Problems that are caused by blood flow that comes back into the heart (regurgitant)

It’s also important to note that innocent and physiological heart murmurs are less dangerous than pathological (meaning caused by heart disease) heart murmurs.

Symptoms of Heart Murmurs in Large Breed Dogs

There are several symptoms of heart murmur in large breed dogs. These include:

  • Racing pulse or an irregular heartbeat
  • A cough that is hacking and persistent
  • Abnormal panting, even while resting
  • A lack of appetite or energy
  • Fainting or collapsing
  • Developing blue gums or tongue
  • Retaining water in an unusual and severe way

If you believe that your dog has a heart murmur or if they are showing symptoms of a heart murmur you should get veterinary help immediately. Catching a heart murmur early often allows for treatment of the underlying condition causing the disease.

Types of Heart Murmurs in Dogs

If your dog is an adult their heart murmur is usually caused by structural heart disease. The following types of heart murmurs are what your vet will typically diagnose.

Left apical systolic heart murmurs: This type of heart murmur is caused by mitral regurgitation which is often caused by myxomatous mitral valve disease (MMVD).
In large breed dogs, this condition can also be caused by dilated cardiomyopathy.

Right apical systolic heart murmurs: This type of heart murmur is caused by tricuspid regurgitation. The most common reason that dogs have tricuspid regurgitation is a chronic valvular disease.

Diastolic murmurs: This type of murmur doesn’t happen often in dogs. When they do occur they are usually related to aortic insufficiency secondary to aortic endocarditis.

Heart Murmur Grading

One of the ways that veterinarians diagnose the cause and severity of a murmur is by using a scale from one to six.

  • Grade 1. Vets can barely hear the murmur when using a stethoscope. These are the least severe types of murmurs.
  • Grade 2. Soft murmurs that your vet can hear when using a stethoscope.
  • Grade 3. This indicates a murmur that can start causing a serious problem. It’s louder than grade 2 and softer than grade 4.
  • Grade 4. These are murmurs that can be heard when listening with a stethoscope on either side of the chest.
  • Grade 5. Very loud murmurs that can be heard easily with a stethoscope, but also can be felt when a hand is held against the dog’s chest.
  • Grade 6. These can be felt through the chest wall, are very loud, and are the most severe types of heart murmurs.

If your dog has a heart murmur, your veterinarian will assign one of these grades to it. The grade it receives will give you an idea of how severe it is. The higher the number, the greater the severity.

Diagnosing Heart Murmurs

Heart murmurs in large breed dogs are almost always diagnosed by a vet using a stethoscope.

Your vet will listen to your large breed dog’s heart and will evaluate how loud the murmur is and where it’s located in the heart. This will help the vet determine what kind of murmur your dog has.

Once your vet knows the type of murmur, he/she will then attempt to determine the cause of the murmur.

The vet will look at factors like the dog’s breed, age, health, and medical history. There are certain breeds of dogs and certain diseases that create conditions for specific types of murmurs.

If your dog is a puppy it may have an innocent murmur that resolves with age. If they are older your dog might have a condition that is causing the murmur. The underlying condition is usually the thing that requires treatment.

Sometimes vets have to do additional testing to determine the underlying condition. Electrocardiograms, radiographs, and echocardiograms are all tools that your bet may use to figure out where the heart murmur is coming from.

Treatment of Heart Murmurs in Large Breed Dogs

Vets don’t actually treat heart murmurs. They manage the symptoms and treat the problems that come with having a heart murmur.

Heart murmurs are usually related to another underlying condition the dog is dealing with and treatment options will depend on that condition. The types of conditions that can cause heart murmurs can vary greatly. For instance, hyperthyroidism is going to be treated very differently from heartworm.

Fortunately, minor heart murmurs will occasionally resolve on their own, even in adult dogs.

Will My Dog Survive a Heart Murmur?

Heart murmurs can be very scary and they can be serious. But you shouldn’t panic. If your dog has a heart murmur there are likely treatment options for the underlying conditions, although older dogs often have a worse prognosis than younger dogs.

Catching a heart murmur is the first step to treatment. If you believe your dog may have a heart murmur make sure to get them to the vet for diagnosis as soon as you can.

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