Signs & Symptoms of Dilated Cardiomyopathy in Dogs

Dilated cardiomyopathy is a degenerative disease of the heart, where the heart muscle weakens. Affected dogs typically will develop congestive heart failure. Different potential causes exist, but genetics may influence the disease.

In dilated cardiomyopathy, the heart muscle becomes thinner and weaker. The heart chambers expand -- or dilate -- and the heart cannot pump effectively. Valves may leak, and heart failure often develops. Some breeds appear to be predisposed to developing dilated cardiomyopathy, namely boxers, Doberman pinschers and cocker spaniels. According to the American Kennel Club, most cases of dilated cardiomyopathy don’t have an identifiable cause. Taurine deficiency is a common cause in cocker spaniels and boxers, while certain medications can weaken the heart muscle.

Many dogs affected with dilated cardiomyopathy don’t show signs of the illness during early stages. As such, potentially affected dogs should be screened regularly. Difficulty breathing or heavy panting are signs of dilated cardiomyopathy, or you may notice your dog coughing. Dogs start to develop exercise intolerance, where they can’t run or play as long as they used to. As your dog’s heart fails, you may notice his abdomen expanding, as fluid accumulates. Your dog may suddenly pass away without any signs.

On exam, your veterinarian may hear a heart murmur caused by the heart valves leaking. Your veterinarian can perform certain tests to diagnose dilated cardiomyopathy, although she may recommend you take your dog to a canine cardiologist. With chest radiographs, commonly called x-rays, your vet can measure your dog’s heart to see if it is larger than normal. Radiographs also allow for evaluation of the lungs and vessels around the heart. Electrocardiograms show if the heart is beating normally, while your veterinarian can have an echocardiogram completed to evaluate the heart muscle diameter and chamber size. Some dogs need to wear a 24-hour Holter monitor to check for arrhythmias that can accompany dilated cardiomyopathy.

Dilated cardiomyopathy cannot be cured, but many cases can be managed -- for a period of time -- with drug therapy, although the disease typically progresses. If your dog has developed heart failure, furosemide -- commonly called Lasix -- may be given to remove edema. ACE inhibitors include enalapril and are often given to help stave off the development of heart failure. If your dog is having arrhythmias with his dilated cardiomyopathy, medication to modulate the occurrence may be used, such as calcium channel blockers. Digoxin or pimobendan may be used to help the heart contract more optimally. Blood work is often needed with drug therapy to ensure that the kidneys are not being affected by the medication.