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

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

Dilated cardiomyopathy is a disease characterized by an enlarged and weakened heart. This condition has many potential causes and potentially severe effects. In this post, our Bonita Springs Cardiology team will guide you through this serious condition's causes, symptoms and treatments. 

What is dilated cardiomyopathy?

Dilated cardiomyopathy is a serious condition which describes the expansion and weakening of the lower chambers of the heart (ventricles), and in some cases progressing to cause enlargement of the upper chambers (atria). 

A dog’s heart will expand in this way when it is unable to properly contract and pump blood to the rest of the body. Blood accumulates in the heart and the pressure pushes at the outer walls and valves of the heart, expanding it and thinning its outer walls. 

When a pet's heart is enlarged in this way, it becomes even more difficult to pump blood around the body and to the organs that need it. As this condition progresses, the other organs, especially lungs, will often begin to reduce in function. This progression is what makes dilated cardiomyopathy very serious.

The causes of dilated cardiomyopathy

This condition may appear in any dog age or breed, however, it is much more common in dogs between the ages of four and ten years old. This condition can also occur in cats. 

While there is not always an identifiable cause for dilated cardiomyopathy, there are a number of known factors which can contribute to the condition in your pet. Nutritional deficiencies in pets fed a grain free or boutique diet have more recently been shown to dilated cardiomyopathy.

As well, other factors such as infectious diseases, genetics play a major role in some breeds of dog, especially large breeds. Doberman Pinschers, Boxers, Great Danes, Irish Wolfhounds, and Cocker spaniels are some breeds which are genetically predisposed to DCM.

The symptoms of dilated cardiomyopathy

Symptoms of dilated cardiomyopathy 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 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

Diagnosing an enlarged heart


A chest x-ray of your pet may reveal abnormalities in their heart and lungs such as an enlarged heart or the presence of fluid in the lungs or chest cavity. Both of these can be indicators of dilated cardiomyopathy.


This test monitors the electrical impulses which create your pet's heart beat. This test can reveal heart rhythm issues such extra or dropped heartbeats or an abnormally fast heart rhythm, such as ventricular tachycardia or atrial fibrillation. 


This diagnostic test uses ultrasound to monitor the size and function of your pet's heart in real-time. This test allows our vet cardiologists to check your pet's heart for structural problems or reduced strength of the heart’s contractions.

Treatment of dilated cardiomyopathy

Treatment of an enlarged heart depends almost entirely on the root cause of this condition in your specific dog. If it was brought on by nutritional issues, 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 pets suffering from breathing issues brought on by fluid in their lungs, they may require oxygen therapy until the fluid drains from their lungs, because of a prescribed diuretic, or because our cardiologist drains them manually. 

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

While there are some correctable causes of dilated cardiomyopathy, in most pets this is progressive with no cure. In these cases, treatment is aimed at lengthening your treasured companion’s life and making it as comfortable as possible.

Is your dog showing symptoms of an enlarged heart? Our qualified veterinary specialists offer cardiology services for your pet. Speak to your primary care vet for a referral or contact us for more information.

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