Dogs with Enlarged Hearts (Dilated Cardiomyopathy): Causes, Treatments & Symptoms

Dilated cardiomyopathy — or an enlarged heart — is a condition that can affect dogs with a wide variety of causes and potentially severe effects. Here, our veterinary specialists explain this serious condition's causes, symptoms and treatments to our Boulder and Denver area clients. 

What is an enlarged heart in a dog?

An enlarged heart in your dog is a serious medical condition that describes the expansion of the lower chambers of their heart or, less commonly, its upper chambers. 

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 your dog's heart becomes enlarged, it becomes quite difficult for it to pump blood around their body. As this condition progresses, the dog's organs, especially their lungs and kidneys, will often start reducing in function. This progression is what makes dilated cardiomyopathy a very serious medical condition.

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 4 and 10 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:

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

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. 

It can often be difficult to diagnose this condition in its earliest stages. However, your veterinarian may be able to detect its subtle signs over the course of a comprehensive physical exam. Because of this, it is important that you bring your companion in for regular routine care.

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

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

How is an enlarged heart diagnosed in dogs?

While routine physical exams can suggest to your vet that your dog may have an enlarged heart, a final diagnosis will be required for further testing in order to determine if any of the above symptoms are a result of 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 electrical impulses sent to your dog's heart by their brain telling it to beat on time. An irregular heartbeat (also called an arrhythmia) or an abnormally quick heartbeat (ventricular tachycardia) can also be detected using this diagnostic tool.


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 for an enlarged heart depends almost entirely on the root cause of this condition in your pup. It was incited by nutritional issues like taurine deficiency, treatment can start with something as simple as a dietary change or supplements. 

Most often, treatment involves a series of medications and therapies that are intended to strengthen your four-legged companion's heart and allow them to better circulate their blood. For dogs that are suffering from breathing issues caused by a buildup of 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 manually drained depending on the severity of the buildup.

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 associated with an enlarged heart? At Rocky Mountain Veterinary Cardiology our veterinary cardiologists have extensive experience diagnosing and treating dogs with heart conditions. Request a referral from your vet today or contact us for more information.