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Veterinary Teaching Hospital

Dilated Cardiomyopathy (DCM) in dogs

Image of the computer screen on a heart monitor.

What is dilated cardiomyopathy in dogs?

Just like humans, dogs can get a form of heart disease called dilated cardiomyopathy, which causes weakened heart contractions and poor pumping ability. As the disease progresses, the heart chambers become enlarged, one or more valves may leak, and signs of congestive heart failure develop.

What causes dilated cardiomyopathy in dogs?

The cause of dilated cardiomyopathy is unclear in most cases, but certain breeds appear to have an inherited predisposition. Large dog breeds are most often affected, although it also occurs in some smaller breeds, such as cocker spaniels.

Occasionally, dilated cardiomyopathy-like heart muscle dysfunction develops secondary to an identifiable cause such as a toxin or an infection. In contrast to people, heart muscle dysfunction in dogs and cats is almost never the result of chronic coronary artery disease, or heart attacks.

What are the signs of dilated cardiomyopathy?

Early in the disease process, there may be no detectable clinical signs, or the pet may show reduced exercise tolerance. In some cases, a physical examination by a veterinarian can detect abnormal heart sounds and irregular heart rhythm as the disease progresses.

As the heart’s pumping ability worsens, blood pressure starts to increase in the veins behind one or both sides of the heart. Lung congestion and fluid accumulation, or edema, often develop behind the left ventricle/atrium. Fluid also may accumulate in the abdomen or around the lungs if the right side of the heart is also diseased. When these symptoms occur, heart failure is present. Weakness, fainting episodes, and sudden death can result from heart rhythm disturbances.

What are the signs of heart failure in dogs?

Dogs with heart failure caused by dilated cardiomyopathy often show signs of left-sided congestive failure, including reduced exercise ability, tiring quickly, increased breathing rate or effort for the level of their activity, excess panting, and cough (especially with activity).

Sometimes the cough seems soft as if the dog is clearing its throat. Poor heart pumping ability and arrhythmias can cause episodes of sudden weakness, fainting, or sudden death. Some dogs with dilated cardiomyopathy experience abdominal enlargement or heavy breathing because of fluid accumulation in the abdomen or chest.

More advanced signs of heart failure can include labored breathing, reluctance to lie down, inability to rest comfortably, worsened cough, reduced activity, loss of appetite, and collapse.

Signs of severe heart failure may seem to develop quickly with dilated cardiomyopathy, but the development of underlying heart muscle abnormalities and progression to overt heart failure probably takes months to years.

How is dilated cardiomyopathy diagnosed?

A cardiac exam by a veterinarian can detect abnormal heart sounds and many signs of heart failure. Usually, chest radiographs (X-rays), an electrocardiogram (ECG), and an echocardiogram are performed to confirm a suspected diagnosis and to assess severity.

Echocardiography can be used to screen for early dilated cardiomyopathy in breeds with a higher incidence of the disease. Resting and 24-hour (Holter) ECGs are sometimes used as screening tests for the frequent arrhythmias that usually accompany dilated cardiomyopathy in some breeds, especially boxers and Doberman pinchers.

What treatments are available for dogs with dilated cardiomyopathy?

Asymptomatic cases of dilated cardiomyopathy may be treated with medications to slow the progression of the changes leading to heart failure and as symptoms advance. Since the disease is irreversible and heart failure tends to be progressive, medications and dosages usually must be increased over time.

What should I do if my dog is showing signs of dilated cardiomyopathy? 

If your dog is showing any symptoms of dilated cardiomyopathy, you should immediately contact your veterinarian or WSU’s Veterinary Teaching Hospital at 509-335-0711.


This information is not meant to be a substitute for veterinary care. Always follow the instructions provided by your veterinarian. Washington State University assumes no liability for injury to you or your pet incurred by following these descriptions or procedures.