Dilated Cardiomyopathy (DCM)

What is it?

DCM begins with degeneration of the heart muscle, especially the wall of the left ventricle. As the muscle weakens, blood backs up, pressure rises, and the chambers stretch and enlarge. Some dogs develop a murmur or an irregular heart rhythm.

It is the most common cause of heart failure in several large breeds, including Doberman pinschers, Boxers, and Great Danes, as well as Irish wolfhounds, Newfoundlands, Saint Bernards, and standard and giant schnauzers. It is diagnosed more often in males, and small breeds rarely develop it.

The FDA has investigated reports of DCM in dogs, including breeds not usually at risk, that were eating certain diets, many labeled grain-free, with peas, lentils, other legumes, or potatoes high on the ingredient list. The FDA has not established that these foods cause DCM and says it will update the public when meaningful new science is available. If you have questions about your dog's diet, talk with your veterinarian.

What signs should I watch for?

The disease develops slowly, but signs can appear suddenly. Watch for fast breathing at rest or during sleep (more than about 30 to 35 breaths a minute), harder breathing, restless sleep, coughing or gagging, weakness, tiring easily, fainting or collapse, poor appetite, weight loss, a swollen belly, or a quiet, withdrawn attitude.

How is it diagnosed and treated?

Your veterinarian will listen to the heart and lungs and may recommend blood and urine tests, cardiac blood markers, chest X-rays, an ECG or 24-hour Holter monitor, and an echocardiogram, which gives the most accurate picture of the heart. Treatment uses heart medications such as pimobendan, diuretics, ACE inhibitors, and drugs to control abnormal rhythms. In some breeds, taurine or carnitine supplements help, and dogs with diet-associated DCM may improve with a diet change.

Can it be prevented, and what's the outlook?

• DCM is serious, and outlook varies.
• Some dogs do well on treatment for months to a couple of years; Doberman pinschers often have a shorter course.
• Dogs that start treatment before heart failure develops tend to do better, so regular checkups matter, especially for at-risk breeds.