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Enlarged Heart in Dogs: Dilated Cardiomyopathy

Enlarged Heart in Dogs: Dilated Cardiomyopathy

An enlarged heart in a dog - or dilated cardiomyopathy - is a condition with a variety of causes and potentially severe effects. Here, our Thousand Oaks veterinary cardiologists explain this serious condition’s causes, symptoms, and treatments.

What is an enlarged heart in a dog?

An enlarged heart in dogs (or dilated cardiomyopathy) is a serious condition that describes the expansion of the lower chambers of the heart (ventricles) or, less commonly, its upper chambers (atria). 

A dog’s heart will expand when it is unable to properly contract and push blood out to the rest of the body. Blood accumulates in the heart and puts pressure on the outer walls and valves of the heart, causing expansion and thinning of the heart walls. 

When a dog’s heart is enlarged it becomes difficult for your pup's heart to pump blood around its body to the organs that need it. As the condition progresses the dog’s organs, especially lungs and kidneys, will often begin to reduce in function. This progression is what makes dilated cardiomyopathy very serious.

What causes enlarged heart in dogs?

An enlarged heart may appear in any dog age or breed but is common in dogs between the ages of four and ten years old. 

While there is no definitive cause for dilated cardiomyopathy, there are a number of known factors which can contribute to its development in your pet. Nutritional deficiencies in carnitine and taurine have been proven to factor into the development of an enlarged heart in dogs. 

Other factors, such as infectious diseases and genetics, can also contribute to this condition’s development. Some breeds of dog, especially large breeds, are known to be predisposed to developing the condition, including:

  • Irish Wolfhounds
  • Newfoundland Retrievers
  • American Cocker Spaniels
  • Boxers
  • Dalmatians
  • Doberman Pinschers
  • Springer Spaniels
  • Labrador Retrievers
  • Tibetan Terriers
  • Welsh Corgis
  • English Cocker Spaniels
  • German Shepherds
  • Great Danes
  • Saint Bernards

What are the symptoms of an enlarged heart in dogs?

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

Often, it is very difficult to diagnose in its early stages. However, your vet may be able to detect subtle early signs of this condition in the course of a complete physical examination so it is important to bring your four-legged companion in for regular routine exams.

The following are some of the most common symptoms of an enlarged heart:

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

How is an enlarged heart diagnosed 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 testing to determine if any of 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. An irregular heartbeat (arrhythmia) or 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 is suffering from an enlarged heart. 

What is the treatment for enlarged heart in dogs?

Treatment of an enlarged heart depends almost entirely on the root cause of this condition in your dog. If it was brought on by nutritional issues such as a taurine deficiency, treatment can begin with something as simple as dietary changes and supplements. 

Treatment most often involves a series of medications and therapies intended to strengthen your furry companion’s heart and allow them to better circulate their blood. For dogs suffering from breathing issues brought on by fluid in their lungs, they may require oxygen therapy until the fluid drains from their lungs naturally. They may also be prescribed a diuretic or have their lungs drained manually by a vet.

Unless your dog is continually and severely affected by this condition, long-term hospitalization is usually not required. 

Dilated cardiomyopathy is often a progressive condition and there is no cure. Treatment is aimed at lengthening your treasured companion’s life and making your pet as comfortable as possible.

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

Is your dog at an increased risk of heart conditions, or showing symptoms of an enlarged heart? Our Thousand Oaks veterinary cardiologists have extensive experience diagnosing and treating dog heart conditions. Request a referral from your vet today.

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VSEC Thousand Oaks is accepting new patients! Our board-certified specialists and experienced emergency veterinarians are passionate about restoring good health to animal companions.

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