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Enlarged Heart in Dogs: Causes, Symptoms & Treatment

An enlarged heart (dilated cardiomyopathy) in a dog can be caused by numerous things and trigger many severe side effects. In this blog post, our Dallas vets discuss causes of this serious condition, in addition to symptoms and treatment options.

How do dogs develop an enlarged heart?

Some dogs develop a serious condition referred to as an enlarged heart (the medical term is dilated cardiomyopathy, or DCM). This serious condition occurs when the heart's lower chambers (ventricles), or less frequently, the upper chamber (atria) expand. 

The heart is unable to contract properly and propel blood to the rest of the body, causing expansion. Blood accumulates inside the heart, then pushes on the heart's valves and outer walls, expanding the heart. 

When this happens, your pooch's heart will have more difficulty pumping blood through the body and to the organs. The lungs, kidneys and other organs will start to malfunction as the condition progresses. Dilated cardiomyopathy eventually causes severe side effects for any dog suffering from the condition.

What are signs of an enlarged heart in dogs?

Symptoms of dilated cardiomyopathy in dogs can range from mild to severe as the condition progresses. 

Veterinarians often have difficulty diagnosing this disease in its early stages, since early signs of DCM in dogs do not often appear. Your dog may also experience a long pre-clinical phase when the condition is in its early stages. 

That said, your vet may be able to identify hidden or subtle signs of an enlarged heart in your dog during a clinical examination. That's why bringing your canine friend in for routine exams is essential. If you or your veterinarian do notice symptoms, we also have extensive experience in diagnosing and treating diseases and disorders of cats' and dogs' internal systems.   

If your pet displays symptoms of a cardiological (heart-related) condition, your veterinarian will perform a thorough physical exam to diagnose the problem. We can then develop a detailed treatment plan geared to your pet's specific needs. 

Here are some of the most common symptoms of an enlarged heart in dogs:

  • Abdominal distension
  • Anorexia
  • Coughing
  • Heart murmur
  • Irregular or weak pulse
  • Labored breathing
  • Lethargy 
  • Muffled breathing or crackling sound while breathing 
  • Panting
  • Sudden collapse

What causes an enlarged heart in dogs?

While a dog of any age or breed can experience an enlarged heart, the condition is more typical in dogs between 4 and 10 years old. 

Though an enlarged heart does not have a definitive cause, several factors can contribute to the development of the condition in many dogs diagnosed with DCM. Diet and nutritional deficiencies in taurine and carnitine have been proven to impact dogs' risk of developing the disease. 

Additionally, other factors, including old age, injuries, toxicity, infectious diseases and genetics can play a role in this cardiological condition. Historically, enlarged hearts in dogs tend to co-occur with conditions like congenital heart diseases, heart disease, and congestive heart failure. Understanding the potential causes of these diseases can help you monitor the health of your pup's heart. Deficiencies in amino acids and low thyroid can also be contributors. 

Some dog breeds – especially large breeds – are known to be predisposed to developing this condition due to taurine insufficiency. They include:

  • English Setters
  • Golden Retrievers
  • Labrador Retrievers 
  • Newfoundlands
  • Saint Bernards

Other breeds are genetically prone to DCM, but are not linked to taurine deficiency. These include:

  • Boxers
  • Doberman Pinschers
  • Irish Wolfhounds
  • Great Danes

While large breeds are most likely to develop DCM, an enlarged heart can also become a problem in smaller dogs that have an inherited trait that may predispose them to the condition. These breeds include:

  • English Springer Spaniels 
  • Cocker Spaniels 
  • Portuguese Water Dogs

If your dog is one of these breeds, be cautious about what you're feeding your pooch. the longer you feed your dog the same food, the more likely he or she will be impacted by any excesses or nutritional deficiencies it contains. 

Therefore, to lower your dog's risk of developing an enlarged heart due to nutrition or diet issues, you might consider rotating foods regularly, switching between different brands of foods with different primary ingredients. Foods with primary ingredients of lentils, peas, potatoes, and other legume seeds have been linked to the condition.

Diagnosing an Enlarged Heart in Dogs

While a routine physical examination can suggest to your vet that your pup may have an enlarged heart, a final diagnosis will require further diagnostic testing to determine if the above symptoms are a result of dilated cardiomyopathy.


A chest x-ray of your dog may reveal abnormalities in their heart and lungs such as an unnaturally large heart or the presence of fluid in the lungs. Both of these are strong indicators of dilated cardiomyopathy.


This test monitors the electric impulses which cause your dog’s heart to beat. This test can reveal heart issues such as an irregular heartbeat (arrhythmia) and an abnormally fast heartbeat (ventricular tachycardia) can both be detected using this method.


This diagnostic test uses ultrasound to monitor the movements and shape of your dog’s heart in real-time. This test allows your vet to check your dog’s heart for tinned muscle walls and the efficacy of their heart’s contractions. This is the definitive test to determine whether your canine companion can be diagnosed with an enlarged heart or not.

Treatment of Dilated Cardiomyopathy in Dogs

Treatment may vary depending on the underlying cause of the condition in your dog. If nutritional issues such as taurine deficiency have influenced its onset, treatment may begin with dietary changes and supplements.

Your vet may recommend nutritional therapy, a sodium-restricted diet, coenzyme Q10, or carnitine supplements.

Treatment often involves therapies and a number of medications designed to strengthen your dog's heart, which will assist with blood circulation. Dogs experiencing breathing problems due to fluid in the lungs may require oxygen therapy until the fluid drains naturally from their lungs. Your vet may also prescribe either a diuretic to drain the fluid or do this manually.

However, the condition is progressive and not reversible. It often turns progressive and there is no cure, depending on the underlying cause of your dog's enlarged heart. In these cases, the vet will focus treatment on extending your furry friend's life and making it as comfortable as possible.

Life Expectancy of Dogs with Enlarged Hearts

Long-term prognosis for DCM in dogs varies considerably depending on factors such as your dog's breed, if the disease is related to nutrition, and how severe the disease is at the time it's diagnosed. 

If taurine deficiency is identified and adjusted, the heart's function can improve significantly. However, if your dog is already in congestive heart failure at the time of diagnosis, this may make their prognosis worse.

Unfortunately, most dogs with signs of congestive heart failure when they are diagnosed die as a result of the disease within six months. In the most severe cases, some dogs may survive only weeks to a few months.  A dog with an enlarged heart that's caught in its early stages may have a better prognosis and live a comfortable life for a couple of years. 

Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.

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