Overview 

Dilated cardiomyopathy (DCM) is a serious disease of the heart muscle causing the heart to enlarge and making it more difficult to pump blood. It is one of the most common heart diseases — especially in large and giant breed dogs such as Doberman Pinschers, Boxers, and Great Danes — although other breeds such as Cocker Spaniels may also be predisposed.  

In early stages of the disease, dogs may not show obvious signs of DCM. This can make it harder to detect until it progresses into heart failure — when fluid backs up into the lungs or belly. Veterinarians may recommend screening tests for predisposed breeds to detect DCM sooner, which can improve their prognosis.  

While there currently is no cure for DCM, medications can help delay the progression of disease, manage clinical signs as they occur and improve dogs’ quality of life.  

Causes 

Not all causes for DCM are known, but genetics likely play a large role, particularly in large breed dogs.  

Other causes include nutrient deficiencies (such as taurine or carnitine), which have been noted in Cocker Spaniels and Boxers. More recently, other atypical breeds have developed DCM in association with grain-free diets, and this connection is still under investigation.  

Certain drugs or toxins may also play a role. 

Risk factors 

• Breed predisposition: Doberman Pinschers, Great Danes, Boxers, Irish Wolfhounds, Giant and Standard Schnauzers, Newfoundlands, Portuguese Water Dogs, Toy Manchester Terriers, Cocker Spaniels 

• Middle-to-older aged males 

• Irregular heart rhythms (arrhythmias) 

Clinical signs 

Many dogs will not show obvious symptoms in the early stages of DCM. If there is also an irregular heart rhythm present, they may experience episodes of collapse or even sudden death.  

The clinical signs of DCM after it has progressed to heart failure may include: 

• Increased breathing rate or effort 

• Coughing 

• Weakness  

• Lethargy 

• Weight loss 

• Distended belly 

Diagnosis 

Your veterinarian will need to perform a physical exam and run a few tests to diagnose DCM which may include: 

• X-rays: This can show heart enlargement and changes to the lungs, which may occur due to heart failure.  

• Echocardiogram: This will measure the heart’s enlargement and directly assess its pumping function. 

• ECG (electrocardiogram): This will check for irregular heart rhythms.   

• Holter monitor: This is a device that is worn by your dog, and it continuously measures an ECG for 24 hours instead of at just one point in time. This provides more accurate information about how the heart rhythm varies throughout the day.  

• Blood work: This may be performed to check for any coexisting diseases. 

Treatment 

The goal of treatment is to improve the heart’s ability to pump blood out to the rest of the body. This is managed with medications that help the heart muscle contract more efficiently and help relax the blood vessels, making it easier for the blood to get where it is needed.  

Medications may also be needed to control irregular heart rhythms. When DCM heart failure is present, medications to prevent fluid from building up will also be required. Additional treatments may be necessary to address any underlying causes or conditions. 

Outcome 

DCM does not have a cure, and it can only be managed with medications that can improve and lengthen a dog’s quality of life. An individual dog’s outcome will depend on how early the disease is detected, their breed, underlying causes and how the individual is responding to medication. Some forms of nutritional DCM may reverse with a diet change. The prognosis for dogs with DCM is less favorable after they have developed heart failure. 

Genetic testing of predisposed breeds for their breed-specific variants can help assess risk factors. Since a large portion of dogs with DCM will not show any clinical signs until the disease is more severe, your veterinarian may recommend screening tests for predisposed breeds to detect the disease earlier when treatment is most effective and can improve the prognosis.  

Genetic predisposition 

There are a few known genetic variants in specific breeds, and the most common ones are found in Doberman Pinschers. Two genes known as PDK4 and TTN each have one variant (or mutation), which, when present, may predispose Doberman Pinschers to the development of DCM, especially if the dog comes from an American breeding line. 

Unlike many other inherited conditions that are recessive (when dogs carry one copy of the variant without developing the condition), the PDK4 and TTN variants are dominant. This means that even one copy of the variant can increase the risk of disease.  

Although having at least one of these variants is not a guarantee they will develop DCM, the highest genetic risk for a Doberman exists when both variants are present. Other breeds may also have these variants, but current research suggests that this does not predispose them to DCM in the same way that it does for American Doberman Pinschers. 

This health topic was developed as part of a collaboration between the Cornell Richard P. Riney Canine Health Center and Embark Veterinary, Inc. You can learn more about the hereditary risks of other canine health conditions by exploring our genetics articles.