Dilated Cardiomyopathy (DCM) in Dogs: A Guide to this Heart Muscle Disease

An in-depth guide to Dilated Cardiomyopathy (DCM) in dogs. Learn about this serious heart muscle disease, the breeds at risk, the signs of heart failure, and the treatments available to manage the condition.

Hello, wonderful pet parents. Today, we're going to discuss a serious heart condition that primarily affects our beloved large and giant breed dogs: Dilated Cardiomyopathy (DCM). This is a disease of the heart muscle itself, and it's important to understand because the early signs can be very subtle. Let's get into it.

What is Dilated Cardiomyopathy (DCM)?

"Cardio" means heart, "myo" means muscle, and "pathy" means disease. So, cardiomyopathy is a disease of the heart muscle. "Dilated" means enlarged.

In DCM, the walls of the heart muscle become thin and weak, particularly the ventricles (the main pumping chambers). A weak, thin-walled heart can't contract with enough force to pump blood effectively to the rest of the body. To compensate, the heart enlarges (dilates), but it becomes an inefficient, floppy pump.

This leads to two major problems:

  1. •Decreased cardiac output: The body doesn't get the oxygen-rich blood it needs.
  2. 1Congestive heart failure: Blood "backs up" in the system, causing fluid to leak into the lungs (pulmonary edema) or the abdomen (ascites).

DCM is a progressive disease, and it's one of the most common causes of heart failure in large breed dogs.

Breeds at High Risk for DCM

Genetics play a huge role in DCM. While any dog can get it, some breeds are highly predisposed:

  • •Doberman Pinschers (this is the poster child for DCM)
  • •Great Danes
  • •Boxers
  • •Irish Wolfhounds
  • •Cocker Spaniels (a smaller breed exception)

In recent years, there has also been a link identified between DCM and certain "grain-free" or "boutique" diets that are high in legumes, peas, or potatoes. This is often called nutritional or diet-associated DCM.

Spotting the Signs of DCM

The scary thing about DCM is that in the early stages (the "occult" or hidden stage), there are often no outward signs. A dog can seem perfectly healthy, but the disease is already progressing. This is why screening is so important in high-risk breeds.

When the disease progresses and the heart starts to fail, you will see signs of congestive heart failure:

  • •Lethargy and Weakness: Your dog may seem tired all the time or may not be able to exercise like they used to.
  • •Coughing: A soft, persistent cough, especially at night or when lying down, is a classic sign of fluid in the lungs.
  • •Increased Respiratory Rate: You may notice your dog breathing faster, even when at rest. A resting respiratory rate of over 30-35 breaths per minute is a red flag.
  • •Difficulty Breathing: This is a sign of advanced heart failure and is an emergency.
  • •Fainting or Collapsing (Syncope): This can happen due to poor blood flow or arrhythmias.
  • •Weight Loss: Despite a normal appetite.
  • •A Swollen Belly: This is a sign of fluid accumulating in the abdomen.

If your dog is having trouble breathing, is coughing uncontrollably, or collapses, this is a medical emergency. Get them to a vet immediately.

How Vets Diagnose DCM

  • •Physical Exam: Your vet may hear a heart murmur or an arrhythmia (an irregular heartbeat). They might also hear crackles in the lungs if there is fluid present.
  • •Chest X-rays: These are crucial for assessing the overall size and shape of the heart and for looking for fluid in the lungs.
  • •Echocardiogram (Heart Ultrasound): This is the definitive test for diagnosing DCM. An echo allows a cardiologist to see the thin, weakly contracting heart muscle and to measure how well the heart is functioning.
  • •Electrocardiogram (ECG/EKG): This is used to detect any arrhythmias, which are common with DCM, especially in Boxers and Dobermans. A 24-hour ECG (a Holter monitor) may be recommended.

Treatment: Managing Heart Failure

Unfortunately, there is no cure for the genetic form of DCM. The goal of treatment is to manage the signs of congestive heart failure, improve quality of life, and slow the progression of the disease.

If the DCM is thought to be diet-associated, the first step is to change the diet to a grain-inclusive food from a well-established manufacturer and supplement with an amino acid called taurine. Some dogs with nutritional DCM can have a complete reversal of their heart disease.

For genetic DCM, a cocktail of medications is used:

  • •Diuretics (like Furosemide): These are "water pills" that help to remove the fluid from the lungs.
  • •Pimobendan: This is a miracle drug for DCM. It helps the heart to contract more forcefully and also helps to open up the blood vessels.
  • •ACE Inhibitors (like Enalapril or Benazepril): These medications also help to relax the blood vessels, making it easier for the heart to pump.
  • •Anti-arrhythmic Drugs: If your dog has a dangerous arrhythmia, medications will be used to control it.

Prognosis and Prevention

The prognosis for dogs with genetic DCM is unfortunately guarded to poor once they are in heart failure. The average survival time is typically 6-12 months.

However, for high-risk breeds like Dobermans, screening with an annual echocardiogram and Holter monitor can catch the disease in its hidden stage. Starting medication (like Pimobendan) at this early stage has been shown to significantly delay the onset of heart failure and prolong survival.

DCM is a heartbreaking disease, but by being aware of the risks and the signs, you can be your dog's best advocate.

Sources & Further Reading:

  1. •VCA Animal Hospitals - Dilated Cardiomyopathy (DCM) in Dogs
  2. 1Tufts University Cummings School of Veterinary Medicine - Diet-Associated DCM