Updated February 15, 2024 — Imagine a Great Dane collapses while chasing a ball. A dog sitter notices that a Doberman begins to lag on their regular walk or a golden retriever’s hind legs wobble when going upstairs. These scenes may be indicators of dilated cardiomyopathy (DCM), a potentially fatal heart disease in dogs that develops quickly and without warning.
Understanding the Risk: Breed, Age and Sex Factors
DCM ranks as the second-most common heart disease in dogs, affecting about 1 in 100 dogs across the general population. This translates to an estimated 300,000 to 1 million dogs in the United States living with DCM at any time.
Certain dog breeds, particularly in the United States, are more predisposed to DCM. These breeds include:
- Doberman pinschers
- Irish wolfhounds
- Great Danes
- Boxers
- American cocker spaniels
- English bulldogs
- Golden retrievers
- Saint Bernards
In Europe, the list includes:
- Doberman pinschers
- Airedale terriers
- Newfoundlands
- Scottish deerhounds
- English cocker spaniels
If your dog is a mix of these high-risk breeds, data suggests they are also 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.
Research indicates that DCM is more prevalent in male dogs and typically affects middle-aged to older dogs.
DCM: A Heart Muscle Disease
For pet owners to better understand DCM and how it can affect their dogs, knowing how the heart works is essential.
We all know that the heart's function is to pump blood to every part of the body, sometimes requiring it to pump against gravity and the tone of the blood vessels. The heart is a muscle that has developed to balance size and power.
Heart function declines when the heart muscle starts to deteriorate from age, infections or other factors. This may happen gradually or quickly, depending on the cause. An excellent 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 irregular heartbeats (arrhythmias), contributing to worsening function and clinical signs.
Sensors throughout the body pick up on the decrease in blood flow, and the body will try to compensate for this decline. However, these mechanisms can only help to a point. The changes can worsen the situation in some instances, such as the body increasing tone in blood vessels or releasing substances to increase heart rate.
Causes of DCM in Dogs
A genetic predisposition has long been recognized as a significant factor in the development of DCM. However, hypothyroidism and certain infectious diseases can also cause DCM.
A link between DCM and diet also has received much 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. Due to this, it can be complicated for pet parents to determine what is best for their dog, underscoring the importance of consulting with a veterinarian regarding diet and disease.
Recognizing Clinical Signs
The early clinical signs 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 DCM is an echocardiogram, a real-time, dynamic heart ultrasound. 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 an excellent way to diagnose an irregular heartbeat. Still, because arrhythmias can be intermittent, many veterinary cardiologists now recommend 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 for 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 to look at enzyme changes associated with heart muscle problems. Veterinarians are exploring these tests for dogs suspected of having heart disease. Other diagnostic tests include blood tests available for dogs that look at specific 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 does not help diagnose DCM. However, it can provide information about other organ systems that the disease might impact.
Treatment and Ongoing Research
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 delay the development of CHF significantly. For many dogs, CHF is the inevitable outcome of DCM, but medications are 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, treating those diseases can help improve clinical signs.
Finally, it's essential to examine the diet. Several studies have demonstrated the reversal of many signs of DCM in dogs suspected to have diet-related disease. Pet parents must 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
Areas of research focus on DCM in dogs are:
- Diet and links to DCM
- Genetic underpinnings of DCM
- Early diagnosis
While much research is still focused on links between diet and DCM, one of our active studies is using the gene-editing tool CRISPR to see if it can help change the genetic code of heart cells from DCM-affected Doberman pinschers. If successful, this cutting-edge technology could be the basis for a new treatment in Dobermans with DCM (and possibly translated to other dog breeds).
Another active study that could impact dogs with suspected diet-induced DCM is looking closely at the mitochondria, the cell's "powerhouses," to see if these tiny structures hold the key 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 worldwide survive and thrive!
Read More About DCM and Other Heart Diseases in Dogs
Read More About Diet and DCM
- Diet-associated dilated cardiomyopathy: The cause is not yet known, but it hasn't gone away
- Until more science is available, the FDA will end public updates on the potential link between specific diets and canine dilated cardiomyopathy.
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:
- Feline hypertrophic cardiomyopathy
- Mitral valve disease in dogs
- Arterial thromboembolism in cats
