OVC Cardiology
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Dilated Cardiomyopathy in dogs

What is Dilated Cardiomyopathy (DCM)?

Dilated Cardiomyopathy (DCM) is a Dilated Cardiomyopathy (DCM) is a disease in which the heart muscle becomes weak, the heart becomes enlarged, and heart function is reduced.

DCM is commonly seen in large and giant dog breeds such as Doberman Pinschers, Boxers, Great Danes, and Irish Wolfhounds, but can also affect smaller breeds like Cocker Spaniels.

Screening for DCM is recommended for breeds that are at a higher risk of developing DCM after the age of four.

Male dogs are more commonly affected by DCM than female dogs.

The exact cause of DCM is unknown.

In some dogs, nutritional deficiencies, infections, or toxins can contribute to DCM.

How Does DCM Develop?

The heart has two sides, each with an upper chamber (atrium) and a lower chamber (ventricle).

The left side of the heart pumps the blood into the body.
The right side of the heart pumps the blood into the lungs.
 
In DCM, the heart muscle becomes weak and thin. As a result, the heart cannot pump the blood efficiently.

When blood is not pumped efficiently out of the heart, it can result in pressure build-up in the heart and the lungs, leading to fluid accumulation in the lungs, known as heart failure.
 
Some dogs with DCM may experience abnormal heartbeats called ventricular premature complexes. This condition has a risk of sudden death as the electrical system of the heart is also affected.

In some DCM cases, another type of abnormal heart rhythm called atrial fibrillation may develop.

Both of these conditions can require treatment.


 

Clinical Signs of DCM

DCM progresses through two stages: asymptomatic and symptomatic.

  • Asymptomatic Stage: Diagnosed through screening, with no visible symptoms.
  • Symptomatic Stage: Signs include reduced exercise ability, collapse, coughing, breathlessness, reduced appetite, and weight loss.

Emergency Signs of CHF:

Seek immediate veterinary attention if your dog shows any of these signs.

  • Breathing difficulty
  • Persistent coughing
  • Weakness or collapse

List of Common Signs of DCM:

  • Rapid breathing during rest (more than 30-35 breaths per minute)
  • Increased effort in breathing
  • Restless sleeping
  • Coughing or gagging
  • Weakness
  • Collapse or fainting
  • Weight loss

DCM is a serious disease and can result in sudden death

How is DCM Diagnosed?

Your vet might detect a heart murmur (abnormal heart sound) or abnormal heartbeats during an examination. However, other conditions also result in abnormal heartbeats or heart sounds. Therefore, further testing is required for a definitive diagnosis.

Ultrasound of the heart (echocardiography) is the best method to assess heart size and function.

Radiography (x-rays) can also be taken to evaluate heart size and the possible presence of fluid in the lungs.

An electrocardiogram (ECG) and/or Holter Monitor (24-hour ECG) may also be recommended for your dog to investigate abnormal heartbeats.

Why a murmur is heard in dogs with DCM?

Heart murmurs are abnormal sounds caused by turbulent blood flow, often due to leaky or narrowed heart valves. In DCM, the weakened heart muscle and dilated chambers can cause the mitral or tricuspid valves to leak, creating a murmur.

Ultrasound of the heart (echocardiography) is the best method to assess heart size and function.

Radiography (X-rays) is used to evaluate heart size and if there is fluid in the lungs.

Why Fluid Goes in the Lungs?

In DCM, as the heart muscle weakens and the left ventricle dilates, blood backs up into the left atrium and pulmonary veins. This increased pressure causes fluid to leak from the blood vessels into the lungs, leading to pulmonary edema and difficulty breathing.

Electrocardiography (ECG) and/or Holter Monitor (24-hour ECG) are used to investigate abnormal heartbeats.

Stage of DCM

Stage A

No DCM; dogs at risk of developing DCM.

Stage B1

Reduced heart contractility and/or abnormal heartbeats, and no heart failure.

Stage B2

Enlarged heart, reduced contractility, abnormal heartbeats, no heart failure. Vetmedin® and Enalapril/Benazepril are started to slow DCM progression. Drugs to control abnormal beats might be added.

Stage C

Enlarged heart, reduced contractility, abnormal heartbeats, heart failure. Drugs are added to control heart failure.

Stage D

Enlarged heart, reduced contractility, abnormal heartbeats, heart failure that is difficult to control, medications might be added.

How does DCM affect daily Activities and Quality of Life?

Initially, dogs with DCM may show reduced exercise tolerance or collapse. As the disease progresses, symptoms like coughing, difficulty breathing, reduced appetite, weight loss, and lethargy become more evident, significantly impacting the quality of life.

What is the prognosis for dogs with DCM?

The prognosis for dogs with DCM varies. Early-stage dogs may live for several years with appropriate treatment, while those with advanced disease have a more guarded prognosis. Dogs with CHF typically have a shorter lifespan.

What are the treatment options for DCM?

There is no cure for DCM. Treatment aims to manage symptoms and slow disease progression.

Effective management of Dilated Cardiomyopathy (DCM) involves a combination of medications to support the heart and manage symptoms at different stages of the disease.

Before Heart Failure:
  1. Pimobendan (Vetmedin®):
    • Function: Improves heart contractility and slows the progression of DCM.
    • Benefit: Helps the heart pump more efficiently, delaying the onset of heart failure.
  2. ACE Inhibitors (e.g., Enalapril, Benazepril):
    • Function: Expand veins leaving the heart and reduce resistance, making it easier for the heart to pump blood.
    • Benefit: Supports the heart and slows the progression of DCM.
  3. Beta Blockers (e.g., Sotalol, Atenolol):
    • Function: Control abnormal heart rhythms.
    • Benefit: Stabilizes heart rhythm and prevents complications from arrhythmias.
  4. Nutritional Supplements:
    • Taurine: If a dog has a diet-associated DCM, meaning that DCM was caused by a lack of adequate amounts of Taurine in the diet, a Taurine supplement might be added to the treatment.
    • Benefit: Supports heart muscle function and overall cardiac health.
If Abnormal Heartbeats are Present:
  1. Antiarrhythmic Drugs (e.g., Mexiletine, Amiodarone):
    • Function: Control irregular heart rhythms.
    • Benefit: Prevents complications and stabilizes heart function.
If Your Pet is in Heart Failure:
  1. Furosemide (Lasix®):
    • Function: Removes excess fluid from the lungs.
    • Benefit: Eases breathing and reduces fluid buildup associated with congestive heart failure.
  2. Spironolactone:
    • Function: Supports the heart and slows the scarring process.
    • Benefit: Reduces fluid retention and supports heart function.
  3. Additional Medications:
    • Diuretics: Help manage fluid buildup in the lungs and abdomen.
    • Inotropic Agents (e.g., Digoxin): Increase the force of heart contractions.
  4. Dietary Management:
    • Low-Sodium Diets: Helps prevent fluid retention.
  5. Regular Monitoring and Adjustments:
    • Frequent Veterinary Check-ups: Necessary to monitor the condition and adjust medications as needed.
    • Home Monitoring: Keeping track of your dog’s resting breathing rate and overall condition.

Monitoring and Managing DCM at Home

Breathing Rate Monitoring:

Check resting breathing rate. An increase may indicate worsening CHF.

To easily track your dog’s resting respiratory rate, download the app “Cardalis” from the App Store or Google Play.

How to count resting respiratory rate?

When your dog is resting or asleep, watch their chest move as they breathe. One rise and fall means one (1) breath. Count how many breaths your dog takes in 15 seconds, and multiply this number by four (4) to obtain the total breaths per minute. For example, if you count 4 breaths in 15 seconds, the respiratory rate is 16.

Regular Check-Ups:

Follow your veterinarian’s schedule for re-evaluations and medication adjustments.

Medication Administration:

If you have difficulty giving the medication to your dog, you can use low sodium treats or pill pockets to make it easier.

Exercise:

Moderate exercise is recommended but should be tailored to the dog’s condition. Avoid strenuous activities.

Diet:

Follow your veterinarian’s dietary recommendations, possibly including sodium-restricted diets.

Environment:

Ensure a calm, stress-free environment with easy access to food, water, and resting areas.

 FAQs about DCM

Can my dog with DCM be anesthetized for other procedures?

Each case of DCM is different, and depending on the progression of the disease, there might be additional risks with anesthesia. It is best to consult your veterinarian about the potential risks and precautions.

Is DCM hereditary?

Yes, DCM is considered hereditary, especially in predisposed breeds. It is not recommended to breed dogs with a history of DCM to prevent passing the condition to offspring.

How long will my dog live with DCM?

The progression rate of DCM varies. Dogs with early-stage disease may live for several years with appropriate treatment, while those with advanced disease typically have a shorter lifespan.

Managing DCM in dogs involves understanding the disease, regular monitoring, and appropriate treatment. By working closely with your veterinarian and following their recommendations, you can help improve your dog’s quality of life and manage the symptoms of this challenging condition.