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Dilated Cardiomyopathy in Dogs: Signs & Causes (Vet Answer)

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By Dr. Emma Chandley

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Dr. Emma Chandley

BVetMed PGCertSAS MRCVS (Veterinarian)

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Dilated cardiomyopathy is a disease that affects the muscle of the heart. It is one of the most common heart diseases in large breed dogs. Dilated cardiomyopathy causes the heart to become enlarged while the muscles of the heart become weaker, therefore getting thinner and stretched out. Dilated cardiomyopathy is a slow, progressive disease. It develops gradually and can be some time before clinical signs are witnessed. The function of the heart is compromised as the disease gets worse.

There is no cure for dilated cardiomyopathy, however, it can be managed with medication. The earlier the diagnosis, the better the prognosis. Dilated cardiomyopathy can cause sudden death in some dogs even before clinical signs have been reported by owners.

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What Is Dilated Cardiomyopathy?

Dilated cardiomyopathy is a serious heart condition that affects the pumping mechanism of the heart. It occurs from the progressive loss of myocyte (muscle cells) numbers, which reduces cardiac contractility. The heart muscle degenerates over time resulting in thinner heart muscle walls, especially the thicker muscle of the left ventricle.

The pressure of the blood pumped inside the heart physically stretches the walls of the heart so gradually dogs develop an enlarged, flaccid heart which is incapable of pumping blood around the body efficiently.

It can affect any breed of dog but is more commonly seen in large and giant breeds and some spaniel breeds. In many cases, the disease goes undetected for long periods of time as its progression is subtle and gradual. When clinical signs are eventually noted, there are often severe changes within the muscles of the heart. Nowadays there are special screening programs that are used in dogs with a known genetic predisposition.

sick border collie dog at the vet clinic
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What Are the Signs of Dilated Cardiomyopathy?

Signs of dilated cardiomyopathy can vary greatly. Signs may seem to come on suddenly or they can be subtle and gradual in onset.

Signs can include:

  • Increased breathing rate at rest
  • Abdominal effort when breathing
  • Coughing
  • Retching/gagging
  • Reduced exercise tolerance
  • Disrupted sleep, restless at night
  • Lethargy/weakness
  • Fainting episodes
  • Collapse
  • Reduced appetite
  • Weight loss
  • Muscle loss
  • Altered mentation/less interactive
  • Sudden death

Annual checkups with your veterinarian are recommended, especially if you have a breed of dog that is known to be predisposed to this condition. Your vet will be able to identify early signs of heart disease before clinical signs become apparent. There is a much better prognosis if this is done as early as possible.

What Are the Causes of Dilated Cardiomyopathy?

There are several different factors thought to cause dilated cardiomyopathy. These include:

  • Genetics
  • Infections
  • Nutrition
  • Secondary causes such as hypothyroidism and hypoadrenocorticism
  • Other heart conditions such as myocarditis
  • High doses of a chemotherapy medication such as doxorubicin
  • Idiopathic cause

We know there is a genetic component as the disease appears much more often in certain breeds such as Doberman Pinschers, Boxers, Irish Wolfhounds, Saint Bernards, Newfoundlands, English Springer Spaniels, Cocker Spaniels, and Portuguese Water Dogs.

There have been some recent studies suggesting grain-free diets, boutique dog food, or exotic dog foods may be linked to dilated cardiomyopathy. Vegetarian and vegan diets may also increase the risk, however, there is currently no cause-and-effect relationship proven and there may be other contributing factors.

a veterinarian checking a sick dog using a stethoscope
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How is Dilated Cardiomyopathy Diagnosed?

There are several different tests that can be used to aid in the diagnosis of dilated cardiomyopathy. Various tests assess different aspects of the overall functioning of the heart.

  • Chest auscultation: Your vet will listen to your dog’s chest with a stethoscope initially. The rate and rhythm of the heart will be noted along with any abnormalities. Your vet will be able to identify any heart murmurs—these are audible noises as the blood flow regurgitates through the valves that are unable to close properly due to the altered shape of the heart. Your vet will be able to locate the murmur and give it a grade out of 6. This will give more information about how severe the murmur is. Your dog’s lungs will also be assessed using the stethoscope.
  • Blood and urine tests: These will be used to analyze blood cell counts and also assess the function of the organs. Most importantly the function of the kidneys and the liver will be assessed as these are often affected by heart problems. Another blood test that can be carried out is ProBNP. This test measures the levels of a protein that changes when there are structural changes in the heart. It can indicate heart disease is present although it is not reliable on its own.
  • Chest X-rays: These will allow your vet to assess the size and shape of the heart. There are some classic changes that occur with dilated cardiomyopathy, and these can be seen on an X-ray.
  • Ultrasound of the heart (echocardiogram): This allows for the assessment of the size and shape of the heart and the thickness of the walls. The pumping ability of the heart can be measured as well.
  • Holter monitor: This is a 24-hour monitoring device that is worn by your dog. This records the rate and rhythm over a period of 24 hours to note patterns.
  • Electrocardiogram: This allows for the assessment of the electrical activity of the heart and the rate and rhythm.

How Do I Care for a Dog with Dilated Cardiomyopathy?

There is no cure for dilated cardiomyopathy, however, there are lots of treatment options that can be used to slow down the disease process and control symptoms. The treatment given to your dog depends on the severity of the disease.

If a diagnosis has been made, but there are no clinical signs yet, a drug called Pimobendan can be used. Pimobendan is a benzimidazole-pyridazine derivative that is thought to slow down the disease progression by helping the heart pump more efficiently. In some cases, Enalapril or benazepril can be used; these are angiotensin-converting enzyme inhibitors. Another option is Sotalol which is an antiarrhythmic drug.

If clinical signs are apparent or your dog is in heart failure, there are various treatment options:

  • Pimobendan helps the heart pump more efficiently.
  • Diuretic drugs such as Furosemide or Spironolactone. These drugs help to remove fluid from the lungs and stomach that can accumulate with heart failure.
  • ACE inhibitors such as Benzepril, these help to relax the arteries and veins to lower blood pressure.
  • Antiarrhythmic drugs can also be used if an irregular heartbeat is present.
  • It is thought that some dogs diagnosed with dilated cardiomyopathy can benefit from supplements such as fish oils, Taurine, and L-carnitine. Always consult your vet before adding any sort of supplements to your dog’s diet.
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Frequently Asked Questions

How long can dogs live with Dilated Cardiomyopathy?

The life expectancy of a dog with dilated cardiomyopathy depends on how far along the disease has progressed. Some dogs respond well to treatment, others will have a lower quality of life. One study concluded Doberman Pinschers survived on average 52 days while other breeds survived significantly longer. Another study concluded overall prognosis was poor with survival rates of 17.5% at 1 year and 7.5% at 2 years.

Can Dilated Cardiomyopathy cause sudden death in dogs?

Dilated Cardiomyopathy can unfortunately cause sudden death in dogs. There may have been no clinical signs noted at all by the owner. It is thought to be caused by arrhythmias present as a result of changes in the structure of the heart. The main cause of sudden death in dogs with the disease is thought to be ventricular tachyarrhythmia.

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Can you exercise a dog with Dilated Cardiomyopathy?

Light exercise, for example short, controlled lead walks is appropriate. Anything more strenuous should be avoided. Stop if your dog seems at all tired. Avoid any situation where your dog may become exhausted and be especially wary in hotter weather.

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Dilated Cardiomyopathy is a common and serious disease in dogs. Dogs can have the disease but be asymptomatic for years. Even if there are no clinical signs, sudden death can still occur. There are various treatment options and lots of dogs will continue to live a good quality of life. Treatment aims to reduce clinical signs or delay the onset of heart failure.

Sadly, there is no cure for dilated cardiomyopathy and most dogs affected do eventually die from the disease.

Featured Image Credit: Zontica, Shutterstock

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