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August 17, 2023 — A Great Dane suddenly collapses while chasing a ball. A dog sitter notices that a Doberman in their care starts lagging behind on their normal walk. A golden retriever’s hind legs start to wobble when going up stairs. All these examples can be signs of dilated cardiomyopathy, a form of canine heart disease that can quickly – and quietly – develop into a life-threatening problem. 

Breed, Age and Sex Can Affect the Risk
DCM is the second-most common heart disease affecting dogs. According to some estimates, about 1 in 100 dogs in the general population will be diagnosed with the disease in their lifetime. Put a different way, other statistics suggest, based on the reported frequency of the disease, roughly 300,000 to 1 million dogs in the United States are living with DCM at any given time.

Certain dog breeds have a reported higher risk for the disease. In the United States, these include:

  • Doberman pinschers
  • Irish wolfhounds
  • Great Danes
  • Boxers
  • American cocker spaniels
  • English bulldogs
  • Golden retrievers
  • Saint Bernards

In Europe, breeds with a higher incidence are:

  • Doberman pinschers
  • Airedale terriers
  • Newfoundlands
  • Scottish deerhounds
  • English cocker spaniels

If your dog is a mix of these high-risk breeds, data suggests they also are at higher risk of DCM. Usually, we think of mixed-breed dogs as having a lower risk of certain breed-associated diseases but that doesn't appear to be the case for DCM. 

Several studies show that males have a higher risk of disease. DCM also is most common in middle-age to older dogs.

DCM Is a Heart Muscle Disease
For pet owners to better understand DCM and how it can affect their dogs, it's important to know a bit about how the heart works

We all know that the heart's function is to pump blood to every part of the body, and this requires it to pump against gravity sometimes and against the tone of the blood vessels. The heart is essentially just a muscle, one that has developed to balance between size and power. 

When the heart muscle starts to deteriorate from age, infections or other factors, heart function declines. This may happen gradually or quickly, depending on the cause. A good way to visualize this change is to think of how a balloon loses its elasticity and shape after it's been filled with air a few times and then deflated.  

As the heart muscle weakens, blood cannot effectively pump throughout the body. As the muscle deteriorates, electrical impulse conduction in the heart is also impaired, potentially leading to the development of irregular heartbeats (arrhythmias), therefore contributing to worsening function and clinical signs. 

Sensors throughout the body pick up on the decrease in blood flow and the body will start to try to compensate for this decline. However, these mechanisms can only help to a point and in some instances, such as the body increasing tone in blood vessels or releasing substances to increase heart rate, the changes can actually make the situation worse.

Causes of DCM in Dogs
Because DCM tends to be more common in some breeds than others, a genetic component has been recognized for decades. However, hypothyroidism and certain infectious diseases can cause DCM. 

A link between DCM and diet also has received a lot of attention recently, and researchers are still trying to tease out how diet could lead to DCM. There is a lot of controversy – even among veterinary nutritionists – about links between diet and heart function. It can be very confusing for pet parents trying to determine what is best for their dog. It's important to work with your veterinarian when it comes to diet and disease. 

Clinical Signs Reflect the Decline in Heart Muscle Function
The early clinical signs (symptoms) of DCM are similar to many other types of heart disease and include:

  • Shortness of breath
  • Fatigue, tiring easily
  • Staggering, wobbling, weakness
  • Lethargy

As heart function continues to decline, signs of heart failure can start to manifest. These include:

  • Coughing 
  • Difficulty breathing (dyspnea)
  • Distended abdomen (due to fluid accumulation)

Because the disease can lead to arrhythmias, occasionally sudden death can occur, even in dogs that never exhibited any clinical signs!

Diagnosis Depends on Imaging
The current gold standard for diagnosing dilated cardiomyopathy is echocardiogram, which is a real-time, dynamic ultrasound of the heart. The benefits of this examination cannot be understated. Not only does an echocardiogram help establish a diagnosis but it also provides baseline measurements that can be used to monitor a patient's response to therapy.

We mentioned earlier that many dogs with DCM have irregular heartbeats, a problem that can be fatal. A good old-fashioned electrocardiogram is a good way to diagnose an irregular heartbeat, but because arrhythmias can be intermittent, many veterinary cardiologists are now recommending 24-hour Holter monitoring for dogs with DCM, even in the early stages of the disease. Many people are familiar with this technology, and it remains the gold standard when it comes to catching arrhythmias. 

If you or someone you know has ever had a heart attack or been suspected of having one, you've also likely heard about using a blood test looking for enzymes associated with heart muscle problems. Other diagnostic tests include blood tests available for dogs that look at certain heart biomarkers. We’re still in the early days for many of these tests, but they appear promising in picking up the disease in its early stages and can be used as a screening tool for at-risk dogs who would benefit from further diagnostic tests.

Routine blood work is not helpful for diagnosing DCM but can provide information about other organ systems that might be impacted by the disease. 

Treatment Depends on Disease Stage and Underlying Cause
In dogs diagnosed with DCM who don't have signs of congestive heart failure, starting the drug pimobendan has been shown in several studies to significantly delay the development of CHF. For many dogs, CHF is the inevitable outcome of DCM but there are medications available to help keep dogs comfortable. 

If a dog with DCM has an arrhythmia, additional medication is necessary to control the irregular rhythm. This is true even for dogs who may have no signs of DCM. 

If DCM is suspected to be secondary to another treatable cause, such as infection or hypothyroidism, treatment of those diseases can help improve clinical signs.

Finally, it's important to examine the diet. Several studies have demonstrated the reversal of many signs of DCM in dogs suspected to have diet-related disease. It's important that pet parents work with their veterinarian and consider seeking the assistance of a board-certified veterinary nutritionist to decide what is best for their dog.

Areas of Active Research
Current areas of research focus on DCM in dogs are:

  • Diet and links to DCM
  • Genetic underpinnings of DCM
  • Early diagnosis

While a lot of research attention is still focused on links between diet and DCM, one of our active studies is using the gene editing tool, CRISPR, to see if they can change the genetic code of heart cells from DCM-affected Doberman pinschers. If successful, this space-age technology could be the basis for a new treatment in Dobermans with DCM (and possibly translate to other dog breeds as well).  

Another active study that could impact dogs with suspected diet-induced DCM is taking a closer look at the mitochondria, the cell's "powerhouses," to see if these tiny structures hold keys to the disease. 

From novel therapies to new diagnostic tests: Learn more about how the Foundation is helping advance the science of heart health in dogs.

Studies like these are only possible through donor support Learn more about how you can help animals around the world not only survive but thrive!

Read More About DCM and Other Heart Diseases in Dogs

Read More About Diet and DCM

Take a Listen to Learn More!
Our Fresh Scoop podcast is a great place to find more information about heart disease in dogs and cats. Check out these episodes: