Heart murmurs in dogs — here’s what to expect

Your dog’s health is a high priority in your life, so when your vet tells you during a regular checkup that Spot has a heart murmur, chances are, it scared you a little bit. Certainly, that’s a natural reaction. Any heart-related condition can sound (and be) scary. But the good news is many heart murmurs are manageable and minor, as long as you identify and address the underlying cause. Here’s what you need to know if your dog has a heart murmur.

What is a heart murmur in dogs?

A heart murmur in dogs really isn’t all that different from a heart murmur in humans. Essentially, the murmur itself is a sound initially heard by a stethoscope that indicates something abnormal within the heart as it beats. 

“A heart murmur is the sound heard on auscultation when there is a disturbance in blood flow through the heart,” says Dr. Antje Joslin, DVM, a veterinarian with Dogtopia. “Some heart murmurs occur at a young age and can be due to a heart defect or other abnormality. Some are acquired and tend to come on later in life. Some breeds have a genetic predisposition to certain cardiac abnormalities, and not all of them produce an audible murmur.”

 So, essentially, the murmur is the sound that points to other potential problems. If your veterinarian hears a murmur, chances are they’ll want to send you to get more testing done. With more testing, a definitive cause can be pinpointed, graded (for severity), and addressed through medication or other interventions.

Symptoms of a heart murmur in dogs

Heart murmurs don’t often trigger noticeable symptoms in dogs — or at least, symptoms that might send you running to a vet immediately. Usually, heart murmurs are diagnosed during a regular vet visit when your vet checks your dog’s heart with a stethoscope.

 That said, other symptoms may accompany some heart conditions, and a heart murmur may also be involved. Dr. Joslin specifically says that if your dog shows signs of lethargy, exercise intolerance, loss of appetite, shortness of breath, coughing, gagging, “fainting” or increased respiratory effort, you need to get your pet to the vet. These can be signs of significant health problems, which may include a heart murmur or other underlying heart problems.

Diagnosing the underlying cause of a heart murmur

The reasons your dog might have, or develop, a heart murmur are wide and varied, which is one reason why more testing is critical after an initial diagnosis. “Many heart diseases or defects can cause murmurs in dogs,” says Dr. Joslin. “Murmurs are initially diagnosed when listening to your pet’s heart with a stethoscope. They are often further defined by advanced diagnostics including cardiac ultrasound, ECG, radiographs, and possible blood work that may include heartworm and thyroid testing.”

 Follow-up testing is important because it provides you and your vet with information on the severity of the issue and opens up lines of treatment.

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Heart murmur grades in dogs

One thing to keep in mind is that not all heart murmurs are alike. The severity depends on the underlying diagnosis. 

“Often heart defects are broken down into categories including obstructive, diseased or dilated valves, regurgitant flow and abnormal valves,” says Dr. Joslin. “There are some very mild murmurs that are benign, but certain types of murmurs are due to very serious heart conditions. If your dog has a heart murmur, your veterinarian will give it a grade from one to six, from mild to severe.” While it’s always important to seek testing to understand the cause of the murmur, more serious problems are usually linked to murmurs at grade three or higher.

Causes of heart murmurs in dogs

Of course, the cause of a heart murmur can vary substantially from one dog to another. The causes can be preventable and treatable, as with heartworm disease or nutritional deficiencies, but typically they’re genetic or related to a heart disease you can’t prevent. 

Dr. Joslin emphasizes that it’s important to talk to your vet and get more advanced testing to identify the specific cause of your dog’s murmur.

Outlook for dogs with heart murmurs

As serious and scary as it can be to hear your vet tell you your dog has a heart murmur, it’s important not to get too worried. “Many dogs can live a full, active life with a heart murmur,” says Dr. Joslin. “Luckily, many cardiac conditions can be managed or treated. But make sure you get a full cardiac workup to determine the cause of the murmur. Follow up with annual or biannual exams with your veterinarian.” 

And he adds that if you know your dog has a heart murmur and you notice any of the symptoms related to heart murmurs or heart disease, it’s important to see your vet immediately.