What Is Dilated Cardiomyopathy (DCM) in Dogs?

Medically Reviewed by Kathleen Claussen, DVM on December 05, 2021
3 min read

Dilated cardiomyopathy, or DCM, is a heart disease where the heart muscle becomes weak and has trouble pumping blood through the body. 

DCM is most common in certain large and giant dog breeds

DCM in dogs can affect both sides of the heart, but it’s usually seen on the left side, which is responsible for pushing blood out to the body. As the disease worsens, several problems can develop:

Enlarged or dilated chambers. As the heart muscle weakens and has trouble pumping, blood backs up into the heart and raises the pressure inside. The muscle becomes thin and the pressure stretches it, making the heart swell or dilate.

Leaky valves. As the heart gets bigger and the pressure and blood build up, heart valves start to leak, causing a heart murmur.

Irregular heartbeat. Without strength, the heart muscle starts to beat irregularly and this leads to less blood being pumped through the body. 

Congestive heart failure. As valves leak blood back into the heart, fluid backs up into the lungs and seeps into lung tissue, causing breathing problems. 

It’s not fully clear why dogs get DCM, but a few factors probably play a role, including:

Genetics. Some breeds might have an inherited tendency to get DCM. Large and giant breeds are more likely to get DCM, especially Doberman pinschers, Boxers, and Great Danes. While DCM can happen in smaller breeds like cocker spaniels, it’s less common among them.

Age. Older dogs are also more likely to get DCM; it rarely happens in dogs under age 4.

NutritionSome dogs with DCM don’t have enough of the amino acids taurine or l-carnitine. A deficiency can result if there’s not enough of these amino acids in the diet, or if your dog can’t absorb amino acids properly. 

There are also some reports of DCM in dogs who eat grain-free diets or foods with ingredients like:

  • Peas
  • Lentils
  • Pulses or legume seeds
  • Potatoes 

It’s not clear if or how these foods cause dilated cardiomyopathy, but research into the link is ongoing. 

Infection. Sometimes a bacteria or other infection can lead to DCM. Parvovirus in puppies and some diseases like Chagas disease can cause heart problems, but this is rare. 

Toxins. Some chemicals can damage the heart and lead to DCM. The most common toxin is an anti-cancer drug called doxorubicin. 

In most cases, dilated cardiomyopathy in dogs is genetic and usually happens to certain breeds. 

The disease happens slowly over time and might not show any signs, but DCM symptoms in dogs can come on suddenly. Signs and symptoms vary depending on the stage of the disease and the breed of dog. 

Symptoms include:

Your vet will do a physical exam and listen to your dog’s lungs and heart. If they hear a heart murmur, irregular heartbeat, or odd lung sounds, they will do some testing to confirm. This includes:

Chest X-ray. These scans can show fluid in the lungs.

Electrocardiogram. This test shows the heart’s electrical rhythm and helps find an irregular heartbeat.

Echocardiogram. This ultrasound shows the heart's size and how well it pumps.

Blood tests. These will check certain protein levels that change with heart disease, and liver and kidney function.

If your dog is a breed that tends to get DCM, your vet might want to do routine screening. This usually involves regular check-ups to hear the heart. If there’s an irregular heartbeat, your vet might do 24-hour holter testing to check the heart rhythm. Catching DCM early can help slow the progression of the disease. 

Early treatment can stop the disease from worsening quickly. Your vet may prescribe several types of medications to manage fluid, control the heartbeat, and slow the progression of the disease, including:

  • ACE inhibitors
  • Diuretics
  • Beta blockers
  • Blood pressure medications
  • Cardiac glycosides like digoxin
  • Taurine supplements

Supplements are only for nutritional cases of DCM and don’t treat genetic or other causes. It’s important to talk to your vet about supplements before giving them to your dog. 

DCM changes slowly over time, so with early diagnosis and treatment, your dog can live several years before getting symptoms. 

Talk to your vet about the risk for DCM in dogs and treatment options.