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Heart Murmurs in Dogs

What the Presence of a Heart Murmur Means for the Canine Patient


Heart Murmurs in Dogs

Heart murmurs in dogs can be indicative of serious heart disease or can be completely benign.
Photo Courtesy of _JuanaBanana/Flickr.com

A heart murmur is an abnormal sound that is heard in your dog's heartbeat. It is normally heard with a stethoscope during an examination of your dog by your veterinarian.

Typically, the normal dog heart makes a characteristic "lub-dub" sound as the heart beats. When a heart murmur is present, there will be an abnormal whooshing or swishing noise made during the course of the beat, rather than a crisp "lub-dub" sound.

Causes of Heart Murmurs in Dogs

A heart murmur is heard because of turbulent blood flow. A heart murmur is a sign, not a disease in itself. In fact, there are many different conditions that can cause heart murmurs in dogs.

  • In older dogs, heart murmurs can be caused by malformed valves within the heart that are no longer functioning normally.
  • In large breed dogs, heart murmurs can be caused by diseases of the heart muscle.
  • In puppies and young dogs, a heart murmur may be the result of a congenital structural defect in the heart.

How Serious is a Heart Murmur in a Canine Patient?

A heart murmur may be benign, meaning that it is not serious and no symptoms are present as a result of the murmur. On the other hand, a heart murmur may indicate more serious heart disease. There are a few things to remember about heart murmurs in dogs.

  • Without further diagnostic testing, the severity of a heart murmur cannot be determined.
  • The loudness or intensity of a heart murmur is not indicative of the degree of severity of the murmur.

Diagnostic Tests that Should Be Performed for a Dog with a Heart Murmur

The choice of diagnostic tests that need to be performed to evaluate the severity of a heart murmur depends on several factors, including:

  • the age of the dog
  • the breed of the dog
  • the physical condition of the dog
  • the history of the dog

In most cases, a chest radiograph (x-ray) is a good starting point. Chest x-rays can reveal changes in the size and shape of the canine heart, which can often lead to a diagnosis. Chest x-rays also allow evaluation of the lung fields, allowing the veterinarian to determine whether there is fluid build-up in the lungs that might indicate heart failure.

However, chest x-rays may not be able to adequately evaluate the muscle of the heart. If the dog is a member of a breed that is likely to develop a cardiomyopathy (disease of the heart muscle), an echocardiogram may be indicated in addition to the chest x-ray.

Options for a Dog with a Heart Murmur

If your veterinarian detects a heart murmur for your dog, she will be able to determine which conditions are most likely to be causing that murmur. Your veterinarian will also be able to advise you of the best way to proceed. In most cases, you'll have three options.

  • Some pet owners elect to simply wait and watch their dog if the dog seems healthy otherwise. This may not be a wise choice in all circumstances. There is risk that the murmur could be caused by a serious life-threatening heart disease that could cause a rapid onset of illness.
  • Your veterinarian may be able to perform the necessary testing in her own hospital, especially if the diagnosis is uncomplicated.
  • Your veterinarian may recommend referral to a doctor that specializes in heart disease (a veterinary cardiologist) to have some or all of the necessary testing performed.

Whether your veterinarian recommends referral to a specialist or not will depend on your dog's individual situation, your veterinarian's level of confidence in diagnosing complicated cases of heart disease and the equipment available to your veterinarian in her clinic. For instance, not all hospitals have access to an ultrasound machine which is necessary to perform an echocardiogram.

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