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Enlarged Heart in Dogs: Symptoms, Causes and Treatment

Enlarged Heart in Dogs: Symptoms, Causes and Treatment

An enlarged heart is a serious condition that can affect dogs of any age or breed although it is more common in larger breeds of dogs. Here, our Westminster veterinary cardiologist shares some information about enlarged hearts in dogs and the causes, symptoms and treatment options for this condition.

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 an enlarged heart in dogs?

Enlarged hearts in dogs can develop regardless of age or size although the majority of the cases are seen in older dogs who are of a larger breed.

The main cause of an enlarged heart remains unclear, but there are a number of known factors that 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?

The symptoms of enlarged hearts in dogs can vary in severity along with the symptoms. This is often a condition that is missed 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.

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

  • 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?

Your vet may be able to note subtle symptoms associated with an enlarged heart during your dog's routine checkup. The final diagnosis will require further testing through cardiology 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. These abnormalities are common indicators that your dog may have developed an enlarged heart.


This test monitors the electric impulses that 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 an 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. 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 an accurate diagnosis of your pet's condition, please make an appointment with your vet.

Is your dog facing an increased risk for heart conditions, or showing symptoms of an enlarged heart? Our Westminster veterinary cardiologist has extensive experience diagnosing and treating dogs with heart conditions. Request a referral from your vet today or contact us for more information about specialist care at Choice Veterinary Specialists. 

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