Dilated Cardiomyopathy (DCM) in Dogs – causes, symptoms and life expectancy

The heart is a fascinating organ. On one hand, it is but a simple pump – synchronised contraction and relaxation enabling life-giving blood to travel around the body, again and again and again, potentially over 100 times a minute, for years or even decades. On the other hand, it is such a finely tuned machine that the slightest upset, irregularity or mere seconds of a loss of functionality, can end in death. 

So, when our pet is diagnosed with a heart condition, naturally we will feel anxious – how will it affect them? Will it cause them pain? Will death come sooner? 

The first thing to note is that heart disease is different from heart failure, and though in most cases, the former will inevitably lead to the latter, living a good life with heart disease is entirely possible.  

Within the general canine population, heart disease will affect around 10% of dogs. Dilated cardiomyopathy, or DCM, is the second most common type of heart disease in dogs in the UK, accounting for 21% of diagnosed cardiac cases (mitral valve disease is the most common, accounting for 49% of cases)¹.  

 What causes DCM in dogs?

Dilated cardiomyopathy is a condition where the ventricles of the heart become dilated and the ventricular walls become thinner and weaker, meaning the heart doesn’t contract as efficiently as it should. The definitive cause of DCM is still unknown, but nutrition, infection and genetics have all been implicated. Because the majority of patients with DCM are larger breed dogs, particularly Doberman Pinschers, Great Danes, Irish Wolfhounds and Boxers, it is clear to see that a genetic link is highly likely, though it seems likely that there are many different factors involved.  

The role of nutrition in DCM is an interesting one. It was brought to the forefront in recent years when an unexpected increase in the incidence of DCM was seen in non-predisposed dog breeds who were being fed a ‘grain-free’ diet or one rich in peas or other legumes². Although grain-free diets were blamed in the media, the exact cause has not yet been established, though it is interesting that when many of these dogs were put onto a ‘regular’ diet and monitored, unlike with usual cases of DCM, their DCM appeared to be reversible. Since 2018 when it came to light, the numbers of cases reported has dropped off. This may be because food companies started to change the composition of their diets in the wake of the investigation, or owners moved away from these sorts of diets entirely. Historically, a lack of dietary taurine was also blamed for cases of DCM, though supplementation in the majority of canine diets has since mainly eliminated this as a common cause.  

Ultimately, when feeding a dog with DCM, it is advised to stick to a complete diet, which is nutritionally balanced and will meet all their daily requirements. Diets high in quality animal proteins, rich in Omega 3 fatty acids, and low in sodium are generally thought to be good for overall heart health.  

Symptoms of DCM 

In the early stages, DCM is likely to not have any symptoms, as the heart is able to cope and compensate for the changes. Eventually, though, in those dogs where DCM progresses to cause heart failure you may see symptoms associated with this inability of the heart to efficiently pump blood around the body, as well as with the general overall size increase in the heart. These symptoms will include: 

• coughing 

• breathlessness 

• exercise intolerance 

• excessive panting 

• increased breathing effort 

• distended abdomen (fluid collection) 

With DCM, the stretching of the heart muscle can lead to scarring, a bit like stretch marks in humans. Unfortunately, this scarring can upset the conductivity of the heart and lead to abnormal heart rhythms, known as arrhythmias, which potentially can lead to fainting, or even be life threatening in themselves.  

In some cases of DCM, sadly the first and only symptom seen is sudden death.  

Diagnosis and treatment of DCM 

Diagnosis of DCM is through the use of echocardiography where an ultrasound probe is used to look at the heart and measure wall thickness and contractility. Further evaluation of cardiac arrhythmias can be done by fitting a continuous 24-hour ECG machine known as a Holter vest.  

Treatment is not aimed at bringing about a cure as, with the exception of some of those cases of dietary-related DCM, the structural changes within the heart are non-reversible. However, we can manage any symptoms of heart failure and aim to slow down the progression of the disease. A drug called pimobendan has been shown to improve the contractility of the heart³ and therefore make it more efficient, reducing some of the symptoms seen and slowing the decline in function. Otherwise, standard drugs used in cases of heart failure, such as furosemide, benazepril or spironolactone can be of great benefit in improving a dog’s quality of life.  

Living with DCM 

In the absence of any clinical symptoms, you can continue to treat your DCM dog as normal. However, once symptoms do appear, exercise mediation may be required in order to limit excessive stress on their heart. 

In a veterinary environment, surgery on a dog with known DCM would be a riskier undertaking than operating on a dog without DCM, as it would with any dog with heart disease. But any decision to anaesthetise these animals would always be done after thorough discussion between the owner and the veterinarian, and the risks vs benefits explored in depth. Pre-anaesthetic screening of at-risk breeds could be considered, involving blood samples and echocardiography, which would help to rule out DCM, or highlight asymptomatic changes that would need to be taken into considering before undergoing any procedures.  

Why is my dog with DCM panting? 

As mentioned above, once DCM advances, it may lead to congestive heart failure. Failure of the heart to efficiently pump blood between the heart chambers, or to the lungs, or rest of the body, can lead to fluid backing up, which is clinically seen as either fluid in the abdomen, or fluid on the lungs. Excessive panting can arise for a number of reasons: 

• this fluid will reduce the surface area available within the lungs for gas exchange Moving oxygen in and carbon dioxide out) and therefore reduce the amount of oxygen available in the blood, so the dog will feel ‘out of breath’. 

• fluid collecting around the lungs will restrict their movement so breaths may become fast and shallow. 

• a general lack of efficiency of the heart adds to a lack of oxygen reaching the tissues. So to try and increase the oxygen supply, the dog will tend to pant more.  

Why is my dog with DCM not eating? 

A dog that isn’t eating is one of the most common presentations to the veterinary clinic and can have a multitude of causes. If your dog has DCM and isn’t eating, it may or may not be related to their condition. In fact, in most cases, it won’t be due to the DCM at all, but rather to another more common issue such as gastroenteritis. 

However, for those cases where the DCM has progressed to a severe stage, if your dog stops eating and is obviously unwell, then it could be a sign of the body really struggling to cope and you may need to have a discussion with your veterinarian to assess if further treatment is required.  

Making those hard decisions 

Ultimately, any dog diagnosed with DCM is very likely to have a reduced life span, with survival times ranging from as little as a few weeks to up to 2 years. But a lot will depend on the severity of the condition at diagnosis, whether heart failure is already present, and what breed the dog is, with Doberman Pinschers for example having a less favourable prognosis than other breeds. 

No matter what the predicted life expectancy is, each case must be assessed on an individual basis. Once the quality of life has been lost, humane euthanasia needs to be strongly considered. Quality of life can be hard for many owners to assess, so to help we have lots of information and a quality-of-life questionnaire on our website (Is it time?). We also have a care team phone-line with trained Care Coordinators on hand to help you navigate this very difficult time.  

References 

1. Heart Disease in Dogs; Emily Dutton, Ewelina Korzybska; Vet Times, Volume 51, Issue 46, Pages 4-9

2. https://www.fda.gov/animal-veterinary/outbreaks-and-advisories/fda-investigation-potential-link-between-certain-diets-and-canine-dilated-cardiomyopathy

3. Summerfield NJ, Boswood A, O’Grady MR, Gordon SG, Dukes-McEwan J, Oyama MA, Smith S, Patteson M, French AT, Culshaw GJ, Braz-Ruivo L, Estrada A, O’Sullivan ML, Loureiro J, Willis R, Watson P. Efficacy of pimobendan in the prevention of congestive heart failure or sudden death in Doberman Pinschers with preclinical dilated cardiomyopathy (the PROTECT Study). J Vet Intern Med. 2012 Nov-Dec;26(6):1337-49. doi: 10.1111/j.1939-1676.2012.01026.x. Epub 2012 Oct 18. PMID: 23078651; PMCID: PMC3546380.