Heart Murmur in Dogs: Symptoms, Causes, & Treatments

Heart murmurs in dogs are extra vibrations or sounds in the heart that come from abnormal blood flow. It is not a condition on its own but rather a symptom of an underlying condition. When your veterinarian listens to your dog’s heart with a stethoscope, they’re tuned into two key elements: rhythm and sound. A heart murmur in dogs deviates from the normal heart sounds — those steady “lub-dub” beats that signify a healthy heart working as it should. Instead, what you or your vet might hear is an additional sound that can range from a faint whisper to a pronounced whooshing, swishing, or humming noise occurring between regular heartbeats.

Vets give heart murmurs in dogs a grade of I to VI. Grade I heart murmurs are barely audible, while grade VI murmurs can often be heard even without a stethoscope. It’s essential to understand that the grade of the murmur while important, doesn’t always perfectly correlate with the severity of the underlying heart condition. Vets also classify them based on the location of the strongest intensity and the pattern that the vibrations follow. These classifications, along with any other symptoms your dog may have, help further narrow down the cause of the heart murmur. Accordingly, this better allows your vet to form a proper diagnosis and treatment plan.

Here’s what you should know about the symptoms, causes, and treatments for heart murmurs in dogs.

Symptoms of heart murmur in dogs

Not all heart murmurs in dogs result in apparent symptoms. Some are completely benign and disappear with time. However, many others are associated with heart disease. If you see the signs of heart disease accompanied by a heart murmur, then you must consult your vet immediately.

Here are some signs of heart disease that may appear along with a heart murmur:

• Exercise intolerance

• Lethargy or weakness

• Panting, coughing, or difficulty breathing

• Pale gums or mucus

• Distended abdomen or bloated appearance

• Fainting or collapse

After diagnosing a heart murmur, your vet will likely recommend further diagnostics to understand the cause. These may include X-rays, an echocardiogram, or blood tests. Furthermore, keeping an eye on your dog’s BNP (B-type natriuretic peptide) levels can give you and your vet valuable insights into the state of their heart health and function.

In particular, BNP is a hormone produced by the heart when it’s under stress or strain. High BNP levels are often symptomatic of advanced heart disease, congestive heart failure, or other serious cardiac conditions that require prompt diagnosis and management.

So, what is considered a dangerous BNP level in dogs? Generally speaking, a normal BNP level should be under 900 pmol/L (picomoles per liter). Levels that significantly surpass the normal range, particularly those in the thousands — e.g., above 1,500 pmol/L — can be considered dangerously high.

Causes of heart murmur in dogs

As mentioned earlier, sometimes heart murmurs are benign, and dogs may just grow out of them. Other times, they can result from and indicate more serious medical conditions.

It’s common for young puppies to develop heart murmurs, though these are usually harmless and known as physiologic heart murmurs. They occur when puppies — especially large breeds — grow quickly, and generally disappear on their own after a few months. They cause no symptoms and aren’t a cause for concern.

Heart murmurs in dogs can be also caused by a variety of medical conditions. They can be congenital, result from heart defects, or appear with infections, inflammation, or other diseases.

Here are a few of the conditions that can cause a heart murmur:

• Endocardiosis

• Endocarditis

• Dysplasia

• Cardiomyopathy

• Atherosclerosis

• Anemia

• Heartworm

• Hyperthyroidism

• Valvular stenosis

• Pulmonic stenosis

• Tetralogy of Fallot

• Tumors

Treatments for heart murmur in dogs

Before understanding how to treat heart murmurs in dogs, it’s important to note not all heart murmurs require aggressive treatments. In some cases — especially if your dog is asymptomatic and the murmur is incidental — your vet might recommend a watch-and-wait approach with regular checkups. However, if your dog’s heart murmur is due to a more serious underlying health issue, several treatment options may be considered.

• Medications: If your dog’s heart murmur is associated with heart disease, your vet may prescribe medications to help manage symptoms and slow the disease’s progression. These can include diuretics to reduce fluid buildup in the body, ACE inhibitors to dilate blood vessels, and drugs to control blood pressure and improve heart function.

• Dietary management: Alongside medication, your vet may recommend dietary changes to support your dog’s heart health. This could involve a special diet with reduced sodium to lessen fluid retention or the inclusion of specific supplements to aid heart function.

• Lifestyle adjustments: You might need to make some changes to your dog’s lifestyle to accommodate their condition. Keep them calm and avoid over-exertion. Pay close attention to your dog’s behavior and appetite, and ensure they have a quiet space to rest.

• Surgery: In cases where the heart murmur is due to congenital issues — like a defective heart valve — surgery might be an option to correct the problem. Surgical interventions can be significant, but they may offer a permanent solution to the heart murmur and the underlying cause.

Each case is unique, but many dogs with heart murmurs can live for years after their diagnosis when properly managed. Always remember, early detection and proactive treatment are crucial to ensuring your pet leads a comfortable and happy life, even with a heart murmur.

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