What Does It Mean if Your Pet Has a Heart Murmur?

By: Lauren Strazdis, DVM

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A “heart murmur” is an abnormal sound heard by a veterinarian while listening to the heart using a stethoscope. This sound indicates turbulent blood flow in the heart, meaning that some blood is not flowing smoothly through the heart or in the proper direction. There are many parts of the heart that can be abnormal and lead to a heart murmur. If a heart chamber is dilated, a valve is leaking, or blood is not passing normally into the one of the large blood vessels while exiting the heart, blood turbulence can occur and produce a heart murmur.

Veterinarians classify heart murmurs based on a scale of 1-6, with a grade 1 murmur being the quietest and a grade 6 murmur being the loudest. A high-grade murmur does not always mean a more serious problem compared to a murmur with a lower grade and even low-grade murmurs could indicate significant heart disease. Therefore, it is important to investigate any newly diagnosed heart murmurs or previously diagnosed heart murmurs that suddenly become louder. Finding the cause of a heart murmur allows your veterinarian to address any underlying heart disease and provide appropriate recommendations for treatment and/or management.

The two main tests that veterinarians recommend for evaluating heart murmurs are an echocardiogram (ultrasound of the heart) and radiographs (x-rays).

Echocardiograms are completely painless and can be done while the patient is awake. If needed, mild sedation can be given to keep the patient fully relaxed and comfortable. During the procedure, the heart chambers, valves, and associated blood vessels are examined for abnormal changes. This information can help locate what is abnormal and leading to a heart murmur.

Radiographs reveal any signs of active heart failure, such as fluid in the lungs, as well as the general size of the heart. Many heart conditions can cause parts of the heart to become larger, which can ultimately lead to heart failure. In some cases, medications can be given to prevent heart failure if the heart is enlarged on radiographs.

A heart murmur can have a variety of causes. Some can put an animal’s life at risk by causing heart failure while others may not require immediate concern. For example, certain types of heart murmurs in young puppies can be of no concern and disappear within a few months, while other types can indicate a possible heart defect.

It is always important to follow your veterinarian’s recommendations to give your pet the best chance to have a long, happy, and healthy life.