Heart Murmur in Dogs: Causes, Symptoms & Vet-Approved Diet

Heart murmurs can occur in dogs regardless of their age, sex, size or breed. But don't be alarmed. Not all heart murmurs are harmful. And, even if it is a problem, there are vet-approved diets that can help your dog manage it.

Nonetheless, it's important to know the different kinds of heart murmur in dogs—as some can be serious or a sign of an underlying condition. If you suspect your dog has a heart murmur, always seek veterinary assistance.

In this article, you'll learn what heart murmurs in dogs are, what causes heart murmurs in dogs, and how you can use a vet-approved diet to treat them.

What is a heart murmur in dogs?

A heart murmur is an abnormal heart sound heard when listening to the heart with a stethoscope. They're caused by a turbulent blood flood within the heart [*]. Like us, dogs' hearts pump blood throughout their body. Sometimes, the heart doesn't pump correctly, or a heart valve is stiff, and the heart produces a murmur.

Here's a quick anatomy lesson—the heart has four chambers, like rooms in a house. On the top floor are the right and left atrium, and on the ground floor, the right and left ventricle. Blood moves through the right, heading into the lungs to become oxygenated. And then, back through the left, and out to the rest of the body.

The valves, pumping action, walls and more can each cause heart murmurs in dogs. We'll explain that further below.

Veterinarians grade heart murmurs on an intensity scale from one to six (I-VI). Grade I being the mildest murmurs, and Grade IV being the most severe.

What causes heart murmurs in dogs?

There are two broad classifications of heart murmur in dogs: first, a murmur is determined to be 'innocent' or 'physiologic', and second, the murmur may be 'pathologic' or caused by disease.

More specifically, we can classify heart murmurs in dogs by the physiological cause:

Heart structural abnormalities like valve disease, narrowing of the valves or heart inflammation cause improper blood flow. Some are present at birth; others develop later.

Extracardiac conditions such as anemia, hyperthyroidism, hypoproteinemia, heartworm disease and infection can all alter the blood flow through the heart. Some can even impair the heart's normal functioning.

Innocent heart murmurs are benign, not resulting in any harm. Often, if heard in puppies, the murmur will disappear as they grow. Still, vets may want to listen periodically to ensure the problem doesn't persist [*].

Symptoms of heart murmurs in dogs

Now we know what a heart murmur is; how do you spot one? Well, for that, you need a stethoscope—or really good hearing! It's best to go to a professional.

Nevertheless, the underlying cause of the heart murmur can present in other ways.

Here are some signs and symptoms of hearth murmurs to watch for:

• Coughing
• Lethargy
• Exercise Intolerance
• Panting or abnormal breathing
• Weakness
• Pale gums
• Distended abdomen
• Episodes of collapse

Even if your dog does not show any signs of illness, a murmur can still be present. You should get your dog checked routinely by your vet to monitor.

What is a vet-approved diet for heart murmurs?

A vet-approved diet is a scientifically-backed meal plan created to minimize the risk of heart murmurs in dogs. That means eliminating foods that cause dilated cardiomyopathy and other heart conditions like grain-free diets, and mixing in heart-supporting foods.

Here's how you can get started:

1. Avoid grain-free diets

Grain-free diets often contain a high proportion of peas, lentils and other pulses, as well as potatoes. These foods are associated with canine dilated cardiomyopathy (DCM), which causes the heart's walls enlarge. In 2018, the FDA announced it was inspecting "grain-free" branded pet foods because of their link to DCM.

They stated:

"We understand the concern that pet owners have about these reports: the illnesses can be severe, even fatal, and many cases report eating "grain-free" labeled pet food [*]."

Avoid peas and legumes. These foods are believed to inhibit the uptake of taurine, leading to dilated cardiomyopathy. Try to find a food that includes gluten-free grains like oats, which have not been linked to this dangerous DCM issue.

2. Consume lots of antioxidants

Antioxidants like vitamin C, quercetin and myricetin—just some of the antioxidants contained in cranberries—are renowned for their role in maintaining heart health.

Vitamin C prevents the stiffening of arteries, improves heart oxygenation and enhances overall heart function. Arterial stiffening is one potential cause of heart murmur in dogs.

One review noted, "Overall, current research suggests that vitamin C deficiency is associated with a higher risk of mortality from CVD [cardiovascular disease] and that vitamin C may slightly improve endothelial function and lipid profiles in some groups [*]."

3. Add omega-3 fatty acids

Like antioxidants, omega-3 fatty acids are revered for their heart-preserving effects. In one study, omega-3 supplementation in dogs with myxomatous mitral valve disease improved heart rhythm in dogs and kept them in milder stages of the disease [*].

Indeed, omega-3 fatty acids help preserve arteries and improve overall canine health. A high quality fish oil such as Perfect Wild Alaskan Salmon Oil can help with this.

4. Include coconut glycerin

While it sounds like a chemical, glycerin is found in all fats and can even be produced by the body when there isn't enough of it present.

Glycerin has been consistently found to enhance the performance of athletes and improve heart health. We wrote another article explaining the scientific research done showing how coconut glycerin is a heart healthy supplement. 

What to feed a dog with heart murmurs

It can be scary to learn your dog has heart murmurs. and it's important to take immediate action in their diet.

We covered the 4 main dietary changes to make: avoid grain-free diets, add antioxidants, add omega-3 fatty acids and supplement coconut glycerin.

Our concern for ensuring a dog's heart health is what led us to create Perfect Kibble—a dog food that includes the right amount of all of these. It's a natural whole food diet that's heart healthy and doesn't need to be refrigerated.

While whole food ingredients are ideal, avoid fresh food brands if they include peas or legumes (most do).

The heart is the most important organ. By following these steps, you'll maximize the time your dog has with you.