Dilated Cardiomyopathy (Enlarged Heart) in Dogs

Written by Small Door's medical experts

Dilated Cardiomyopathy, or an enlarged heart, is a type of heart disease that can affect dogs. It’s a serious condition, causing changes to the heart that can be fatal if not treated. It may be primary or secondary to another cause.

In this article:

Owners of dogs predisposed to this disease should be aware of the symptoms so that they can get their dogs the treatment they need as soon as possible. In many cases, catching heart disease early increases the chances of a good prognosis, and as with all conditions, understanding the diagnostic process, treatment options, and management strategies will help you manage your dog’s condition.

What is Dilated Cardiomyopathy (DCM) in Dogs?

Dilated cardiomyopathy is a type of heart disease in which the heart muscle becomes weakened. As a result, the walls of the heart become thinner, and the pressure of the blood inside it causes the chambers of the heart to become abnormally large. Dilation can cause further damage to the heart, including leaking valves, and may also cause irregular heart rhythms. 

These changes to the heart means that it cannot pump blood to the rest of the body effectively,  leading to less oxygen being circulated, causing a decrease in energy, and fluid to develop in the lungs and/or abdomen.

Signs & Symptoms of Dilated Cardiomyopathy in Dogs

The symptoms of dilated cardiomyopathy may vary depending on the case. However, common symptoms include:

  • Exercise intolerance

  • Weakness

  • Cold feet

  • Coughing

  • Appetite loss

  • Increased respiratory effort and rate

  • Loss of muscle mass

  • Fluid in the abdomen

The early signs of dilated cardiomyopathy are difficult to detect, and often go undiagnosed. During this subclinical phase, the body compensates to keep the heart and body functioning, even as the heart’s ability to contract normally decreases.

As the disease progresses, however, symptoms become more obvious and often develop suddenly. You may notice your dog shows less interest in play or exercise, or has difficulty maintaining their previous exercise routine. Weakness is also common, and poor circulation can cause cold feet. Other symptoms include coughing, decreased appetite, noticeably increased respiratory rate and effort, loss of muscle mass, and abdominal swelling from fluid buildup. 

What Causes Dilated Cardiomyopathy in Dogs?

Common causes of dilated cardiomyopathy include:

  • Breed predisposition

  • Nutritional deficiencies

  • Certain diets, including grain free diets and those with exotic ingredients

  • Myocarditis

  • Hormonal problems

  • High dosage of doxorubicin (chemotherapy medication)

  • Idiopathic

Most cases of dilated cardiomyopathy in dogs are idiopathic, which means the underlying cause cannot be found. However, the disease is more common in large and giant dog breeds, as well as a select few small breeds. 

There are a few less common secondary causes of dilated cardiomyopathy. Hormonal issues, like hypothyroidism and hypoadrenocorticism (Addison’s disease) can predispose dogs to the condition, as can high doses of certain chemotherapy drugs and other conditions, like myocarditis. 

Recent studies also suggest that grain-free diets, certain boutique diets, and diets with exotic ingredients may also be linked to dilated cardiomyopathy.

Which Dog Breeds are Prone to Developing Dilated Cardiomyopathy?

Dilated cardiomyopathy is more common in:

  • American and English Cocker Spaniels

  • Springer Spaniels

  • Doberman Pinschers

  • Great Danes

  • Boxers

  • German Shepherds

  • Irish Wolfhounds

  • Scottish Deerhounds

  • Newfoundlands

  • Saint Bernards

  • Labrador Retrievers

  • Portuguese Water Dogs

Doberman Pinschers and Boxers can inherit a genetic form of dilated cardiomyopathy. Similarly, Portuguese Water Dogs can develop a juvenile form of the condition. In most other breeds, however, the disease is more common in middle aged to older dogs.

Taurine and L-carnitine nutrient deficiencies are linked to dilated cardiomyopathy in American Cocker Spaniels, and there is also a link between taurine deficiency and dilated cardiomyopathy in Golden Retrievers and Newfoundlands.

Diagnosing Dilated Cardiomyopathy in Dogs

Diagnosing dilated cardiomyopathy in dogs requires several steps. In severe cases, your dog may need to be stabilized before these tests can be performed. Once the patient is stable, your veterinarian will examine their heart along with organs that depend on the heart for normal function, like the lungs.

If your veterinarian suspects dilated cardiomyopathy, they will most likely recommend a series of diagnostic tests in addition to a physical examination. These tests include chest and abdominal radiographs, an echocardiogram of the heart, electrocardiogram, hormonal assays, analysis of abdominal fluid, blood work, and taurine levels. These tests will reveal how your dog’s heart is functioning, as well as determining whether dilated cardiomyopathy is the cause.

Treatment of Dilated Cardiomyopathy in Dogs

Treatment for dilated cardiomyopathy depends on your dog’s condition and the underlying cause. The most important first step is to make sure your dog is stable, especially in cases of moderate to severe heart failure. This is done with diuretics, oxygen therapy, excess fluid removal, and any other additional measures that may be required.

Then, your veterinarian will discuss starting your dog on oral medications to treat the dilated cardiomyopathy and associated symptoms. These medications include pimobendan, a medication to help the heart pump blood more strongly and help with dilation of the vessels;  diuretics like furosemide (Lasix) and spironolactone; and ACE inhibitors like enalapril or benazepril. The medications are prescribed for lifelong use.

Dogs with an underlying condition causing the heart disease may require further treatment. Taurine supplements, for example, should be used in dogs with deficiencies, and hormone treatment should be started for dogs with hormonal conditions. 

Is there a cure for dilated cardiomyopathy?

It depends. Secondary dilated cardiomyopathy may resolve once the primary condition, like a nutrient deficiency, is treated. However, there is no cure for dogs with primary dilated cardiomyopathy, and prognosis for these dogs varies.

Is dilated cardiomyopathy contagious for humans or other pets?

Dilated cardiomyopathy is not contagious for humans or other pets.

What is the cost for treating dilated cardiomyopathy?

Dilated cardiomyopathy can be an expensive condition to treat. Initial stabilization may require hospitalization and other supportive measures, which can cost hundreds or thousands of dollars. Diagnostic testing can also be quite expensive for this condition, as can the medications used to treat it. Bear in mind that dogs with this disease will require further monitoring and testing for the rest of their lives.

Recovery and Management of Dilated Cardiomyopathy

The prognosis for dogs with secondary dilated cardiomyopathy is generally good, as long as the underlying disease can be identified and treated. However, the prognosis for dogs with primary dilated myopathy is more variable, and depends on their condition. Boxers and Dobermans with inherited heart disease typically only live for a few weeks to a few months after diagnosis. Other breeds can live for a year or longer after diagnosis.

Dogs with dilated cardiomyopathy will require monitoring for the rest of their lives. You can expect your veterinarian to perform repeat testing during recheck appointments to monitor the progress of the disease and any underlying conditions. If your dog responds well to medication, the frequency of these rechecks may be decreased.

In all cases, it is important to avoid feeding dogs with dilated cardiomyopathy high salt foods. Your veterinarian may recommend switching to a low salt diet, and will discuss any other lifestyle accommodations he or she thinks is necessary.

Preventing Dilated Cardiomyopathy

Dilated cardiomyopathy is not a preventable condition. While breeders can attempt to correct bloodlines with demonstrated recurrences of dilated cardiomyopathy through responsible breeding practices, there is little owners can do to prevent dilated cardiomyopathy in their dogs.

However, as discussed above, it’s important to avoid feeding exotic, boutique or grain-free diets (especially those with pea/legume as the protein source).

Is there a vaccine for dilated cardiomyopathy?

No, there is no vaccine for dilated cardiomyopathy.

Summary of Dilated Cardiomyopathy in Dogs

Dilated Cardiomyopathy in dogs is a disease that causes enlargement of the heart, meaning it cannot pump blood effectively. Treatment and prognosis can vary depending on the underlying cause, so it’s important to get your dog checked out by a veterinarian as soon as you notice any concerning symptoms.

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