Dogs with Enlarged Hearts (Dilated Cardiomyopathy) - Symptoms, Causes, and Treatments

Cardiomyopathy (an enlarged heart in a dog) can have many potential causes and several severe side effects. Today, our Ventura vets will explain causes of this serious condition, symptoms and treatment options. 

What is an enlarged heart in a dog?

In dogs, an enlarged heart (or Dilated Cardiomyopathy) is a serious condition that refers to the expansion of the heart’s lower chambers (ventricles) or, less often, the upper chamber (atria).

If the heart is unable to properly contract and push blood out to the rest of the body, a dog’s heart will expand in this way. Blood accumulates inside the heart before pressure pushes at the heart’s valves and outer walls, expanding it. This causes a thinning of the outer walls.

When this occurs, it becomes more difficult for your pooch’s heart to pump blood throughout the body and to the organs that require it. As the condition progresses, organs such as the kidneys and lungs will start to malfunction. The disease’s progression is what makes dilated cardiomyopathy very serious.

Causes of an Enlarged Heart in Dogs

A dog of any age or breed can have an enlarged heart, but the condition is much more common in dogs between 4 and 10 years of age.

While dilated myopathy does not have a definitive cause, many factors can contribute to the development of the condition in your pet. Nutritional deficiencies in taurine and carnitine have been proven to influence the development of an enlarged heart in dogs.

In addition, other factors such as genetics and infectious diseases can play a role in cardiomyopathy in dogs. Some dog breeds - especially large breeds - are known to be predisposed to developing this condition. They include:

  • 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
  • Scottish Deerhounds

The symptoms of dilated cardiomyopathy

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 or hidden signs of this condition in the course of a complete physical examination.

Because of this, it is very important to bring your four-legged companion in to your primary care veterinarian for a routine exam, or to call us if they are unavailable, as soon as you notice symptoms. Our board-certified veterinary cardiologist can perform diagnostic testing to confirm a diagnosis.

The following are the 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

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

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

Often, treatment involves therapies and a series of medications aimed at strengthening your furry friend’s heart, which will help with blood circulation. Dogs experiencing breathing issues as a result of fluid in the lungs may need oxygen therapy until the fluid naturally drains from their lungs. A diuretic may also be prescribed to drain the fluid, or your vet may do this manually.

Long-term hospitalization is typically required unless the condition causes continual and severe side effects in your dogs.

However, depending on the root cause of your dog’s enlarged heart as diagnosed by your vet, the condition is often progressive and there is no cure. In these circumstances, treatment will focus on extending your four-legged companion’s life and making it 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 showing symptoms of an enlarged heart? Our board-certified veterinary cardiologist is trained to diagnose and treat issues in the heart and circulatory system. Speak to your primary care vet today for a referral, or contact our Ventura vets for more information.

Dogs with enlarged hearts cardiomyopathy, Ventura Vets

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