Glossary

Dilated cardiomyopathy

A heart muscle disease in which the heart chambers stretch and the muscle weakens, so the heart pumps poorly; some breeds inherit it.

Also called: DCM, canine DCM, enlarged heart, heart muscle disease

In dilated cardiomyopathy, or DCM, the heart muscle becomes thin and weak and the chambers enlarge, so the heart cannot pump blood effectively. Dogs may seem normal for a long time and then show fatigue, coughing, fast breathing or fainting, sometimes with sudden collapse.

It is mainly an inherited disease of large and giant breeds such as the Doberman Pinscher and the Great Dane. Since 2018 the United States Food and Drug Administration has investigated reports of DCM in breeds that do not normally get it, in dogs eating certain diets, many of them grain-free. A clear cause has not been proven.

Heart ultrasound by a veterinarian or a veterinary cardiologist is the standard way to confirm it. Ask your vet about screening if your breed is prone.

Last reviewed November 8, 2026

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Related terms

Mitral valve disease A slow wearing of the heart's mitral valve that lets blood leak backward, the most common heart disease in older small-breed dogs. Grain-free A dog food made without wheat, corn, rice or other grains, usually replaced by legumes or potatoes; it is not automatically healthier. Ultrasound A real-time imaging test that uses sound waves to show a dog's organs, heart and pregnancy without radiation.