Dilated cardiomyopathy (DCM) is one of the most common heart conditions in dogs. If your dog has been diagnosed with DCM, or even if you have a high-risk breed, it is worth understanding this quietly dangerous disease. 

Dilated cardiomyopathy – what is it? 

DCM is a disease of the heart muscle. Over time, the heart muscle degenerates and become weaker causing the muscular walls of the heart to stretch out and get thinner. The heart then loses its ability to contract properly and it can’t push blood around the body very efficiently. A bit like a balloon that has been overstretched and become saggy.  

It is a particularly nasty disease because the symptoms are often very hard to detect. Outwardly your dog may appear completely healthy, but inside they are hiding a ticking bomb. DCM can cause a sudden heart attack and death, and sadly this sometimes happens before you even know your dog has the condition.   

What causes it? 

Genetics  

There seems to be a strong genetic link with DCM, and genetic tests are available. It is strongly associated with some breeds such as: 

  • Dobermans 
  • Great Danes 
  • Irish Wolfhounds  
  • Other giant breeds 
  • Cocker spaniels 

Diet  

DCM can also be the result of a deficiency of Taurine in the diet. This is more common with dogs on home cooked, vegetarian, or vegan diets, which have not been properly nutritionally balanced.  

Toxins  

Occasionally, drugs can cause toxic damage to the heart muscle, such as Doxorubicin (a chemotherapy drug), and lead to the development of DCM. Fortunately, this is rare.  

Signs of DCM 

DCM develops slowly over time, and the heart is often very damaged before the first signs become apparent. As we have already said, many signs of DCM are silent and can go completely unnoticed by you, the owner. Your vet will be able to detect more signs of DCM with a thorough clinical examination, but in rare cases even this may not reveal any signs of the disease.  

Signs detectable at home: 

  • Lethargy  
  • Exercise intolerance  
  • Fainting or collapsing 
  • Signs of heart failure (e.g. coughing, fast breathing, lethargy, fluid build-up in the lungs or abdomen) 
  • “Heart attack” and sudden death  

Signs often detectable by the vet: 

  • Arrythmias (an irregular heart rhythm) 
  • Poor pulses 
  • Fluid crackles in the lungs, or fluid build-up in the abdomen. 

How is it diagnosed? 

DCM should always be on the radar in high-risk breeds. It is usually diagnosed in middle aged to older dogs, and is more common in males than females. Vets and owners alike should be vigilant for any symptoms developing, and if so, further testing will be warranted.  

Chest x-rays  

Radiographs can show the outline of a very enlarged heart (which is suggestive of DCM) and sometimes fluid build-up in the lungs too. A definitive diagnosis is made with an echocardiogram (an ultrasound of the heart) which shows the internal structure and contractility of the heart. This can detect the disease in its early stages, rather than waiting for symptoms to appear which may not happen until advanced disease, or, until it is too late.  

Blood tests  

Specific tests are also available which can indicate damage to the heart muscle. Although this is not specific for DCM (they may increase with different heart conditions too), it can be a suggestive finding.  

ECG 

Electrocardiograms are useful because as the heart stretches with DCM, its electrical conduction system is often disrupted leading to an irregular heart rhythm. These arrythmias can be serious and need medication to control them.  

How is it treated? 

If the underlying cause is drug toxicity or diet, addressing these factors can reverse the changes to the heart, but sometimes permanent damage is done. Unfortunately, there is no cure for the genetic form of DCM. Once the damage to the heart muscle is done, it cannot be reversed. Sometimes DCM causes a sudden and fatal cardiac arrest, but it can also lead to more chronic ongoing problems such as arrythmias and congestive heart failure.  

Treatment is aimed at supporting the heart to contract, controlling arrythmias, and preventing congestive heart failure.  

  • Drugs – the mainstay of treatment is with prescription medicines. There are several drugs available which your vet can prescribe depending on the specifics of your dog’s condition.  
  • Home management – avoiding strenuous exercise and keeping them at a healthy bodyweight will help protect your dog’s heart from any additional stress. 
  • Nutritional support – heart supplements and prescription cardiac diets are available which aim to support heart function. They will typically be low in salt, high in good quality protein and omega-3 fish oils, and often with Taurine supplementation. 

What is the prognosis? 

The prognosis is variable for DCM depending on the breed and the severity of it. Sudden death from a heart attack or fatal arrhythmia is always a risk, but dogs that go onto develop congestive heart failure can survive anywhere from 6-24 months on average. Medication can certainly improve the survival time for these dogs. Dobermans unfortunately have a particularly poor outlook once they are diagnosed, typically living 2-3 months without treatment, or up to a year with treatment. 

To summarise… 

DCM is a serious condition. For owners of high-risk breeds, proactive veterinary check-ups are key to catching this disease before it becomes life-threatening. Your vet can give you bespoke advice, but they may well recommend regular (i.e. 6-12 monthly) heart check-ups which may include a physical examination to check for any symptoms, a blood test, and an echocardiogram heart scan. Early detection and management of DCM can significantly improve your dog’s prognosis and quality of life.