What is Dilated Cardiomyopathy in Dogs?

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Has your dog been diagnosed with dilated cardiomyopathy (DCM)? It can be a scary thing to hear. DCM is a condition that affects some dogs and eventually can lead to congestive heart failure. Heart disease is something that humans constantly worry about – as it is the leading cause of death in the United States today. Heart disease is often the cause of death by “old age” in humans as well.

Dogs, however, are a bit different. There are a range of different conditions that are the top causes of death in dogs – viruses (like Parvo and Distemper), cancer, and others. But DCM is right up there. As humans, we can watch our diets, get more exercise, and take medication to reduce our risk of heart disease. With dogs, it can be a bit tougher to tell when heart disease is present. Dog owners do their best to ensure that their dogs get enough exercise and eat the right things, but that doesn’t mean they won’t eventually develop different types of heart disease.

What is DCM in Dogs?

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DCM affects the heart muscle in dogs, resulting in weakened contractions and reduced pumping ability. Essentially, DCM is an enlarged heart that does not function properly. Both the upper and lower chambers of the heart are affected, generally with one side more severely affected than the other.

The condition causes the heart chambers to enlarge, leading to the development of congestive heart failure. Congestive heart failure happens when the heart is unable to pump an adequate amount of blood, causing an increase in pressure and fluid that eventually leaks out into the lungs or elsewhere.

This accumulation of fluid in or around the lungs hinders breathing, preventing oxygen from moving into the blood stream. When congestive heart failure happens, your dog will take quick, short breaths in an effort to get enough oxygen. This happens in a downward spiral, as a lack of breathing will prevent your dog from exercising and recovering.

In humans, heart muscle issues are most often the result of coronary artery disease, which causes heart attacks. This is not the case with animals. Sometimes, heart disease is genetic in dogs, and sometimes conditions like DCM happens secondary to another cause, like a toxin or an infection.

How Do Dogs Get DCM?

The cause of DCM in dogs is considered idiopathic – which means that the exact cause of the disease is unknown. There is evidence, however, that certain genetic factors are at play. Most affected dogs are middle-aged, large-breed males – including Doberman Pinchers, Scottish Deerhounds, Cocker Spaniels, Boxers and Great Danes. Though rare, some juvenile dogs develop DCM as well. Young Doberman Pinchers and Portuguese Water Dogs are more susceptible than other breeds.

Symptoms of Dilated Cardiomyopathy in Dogs

There are generally no obvious, immediate sings of DCM – which makes it very difficult to identify early in its progression. A reduced interest in physical activity may occur, but that could be due to a number of reasons. In some cases, your vet may notice a very light heart murmur during a routine physical examination. Again, heart murmur in dogs is not a direct sign of DCM, but it could be one of many early signs. As the disease progresses, signs like these will likely become more pronounced.

As DCM becomes more severe, causing the heart to lose its pumping strength, the dog’s blood pressure increases, putting pressure on the veins and arteries around the heart. Eventually, this leads to fluid in the lungs and abdomen. These factors together can lead to heart failure, which causes weakness, fainting, and even sudden death.

The clinical symptoms of DCM are signs of weakness, lethargy, tachypnea (abnormal rapid breathing), exercise intolerance, cough, anorexia, ascites (abnormal accumulation fluid in the abdominal cavity), and syncope (temporary loss of consciousness usually related to insufficient blood flow to the brain).

Symptoms of Heart Failure in Dogs

Like heart failure in humans, the first signs reveal themselves on the left side of the dog’s body, due to the location of the heart. The dog’s left legs may appear to get weak and then fail. Symptoms of heart failure in dogs also include severely diminished physical activity, an elevated breathing rate and a soft cough. Some dogs with heart failure will have abdominal enlargement due to fluid accumulation.

Dogs with advanced-stage heart failure will show more extreme symptoms, like labored breathing, visible discomfort, worsened cough, inability to lie down, loss of appetite, and, eventually, collapse. If you notice your dog suffering from any of these signs, take him to an emergency vet immediately to determine if the cause is heart failure.

Unfortunately, severe heart failure can develop quickly with DCM – at least on the surface. Underlying heart issues and the progression to heart failure develops over months and years.

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How is DCM Diagnosed?

Your vet will perform an initial physical exam using an echocardiogram to identify the main sign of DCM – a dilated, poorly contracting heart. The echocardiogram is used along with other tests to help rule out false-positives from other present conditions that cause similar echocardiographic findings, including low thyroid level, amino acid deficiencies, inflammation of the heart muscle, or decreased blood flow to the heart muscle.

After the echocardiogram examination, your vet will perform additional medical tests to confirm a diagnosis of DCM, and exclude other possible conditions as reasons for the dog’s symptoms. Radiographic imaging, for instance, can help identify enlargement of the left ventricle and detect the presence of fluid in the lungs.

An electrocardiogram (EKG) may be performed to identify atrial fibrillation and rapid beating of the heart. Blood and urine tests can detect liver and kidney issues in dogs, which often happen due to issues with the heart.

If you have a Boxer or Doberman Pinscher – both breeds with proven genetic predisposition for DCM –  your vet may elect to screen your dog with a 24-hour ECG recording called a Holter monitor. This type of extended monitoring can help identify DCM early in the process. Dogs who are diagnosed with DCM should be removed from breeding programs to stave off future iterations of the disease.

The Holter monitor helps determine the frequency and severity of irregular heart rhythms, so that your vet can design a better course of treatment. Your vet can also perform a DNA test (cheek swab or blood test) to identify the known genetic mutation that causes DCM.

Treatment for DCM in Dogs

Sadly, there is no magic bullet for treating DCM. Once the disease is present, it will most likely continue to progress. As such, treatment for DCM is based around improving the heart function to slow the disease. You vet may prescribe medications to enhance heart contraction and slow down rapid beating, and other drugs to help control the disease, including:

Diuretics: Help to stimulate the kidneys to remove excess fluid from the body.

Angiotensin Converting Enzyme (ACE) inhibitors: These inhibitors work to lower blood pressure and reduce resistance to blood flowing from the heart. They are the more commonly used drugs for heart disease in both humans and dogs, as they are proven to extend life expectancy in both. Enalapril and benezepril are used mostly for dogs, although new drugs continue to be developed.

Digitalis glycosides: These improve heart function by slowing the heart rate and strengthening heart contractions. Digoxin is the most common drug for dogs. Dogs who receive this treatment must be monitored via blood tests and ECG in case of potential for toxic side-effects.

Vasodilators: Used to dilate the arteries or veins so the dog’s heart does not have to work overtime to pump blood, vasodilators are widely used in the therapy of congestive heart failure associated with DCM.

Bronchodilators: Bronchodilators – including theophylline and aminophylline – help dogs breathe more easily when their heart and lungs are incapacitated.

Pimobendan: A new class of drug for the treatment of heart failure and DCM in dogs, Pimobendan is an inodilator (a combination of inotrope and vasodilator) and is also a calcium sensitizer – which helps increase the heart’s ability to contract.

None of these treatment modalities require the dog to be hospitalized, they can be done as outpatient care with your vet.

What is the Prognosis for Dogs with DCM?

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Unfortunately, the prognosis for dogs with DCM is not good. The disease is progressive, and eventually deadly. Even with aggressive treatment, most dogs will end up succumbing to the disease. Dogs who are diagnosed early, however, have a much better chance of keeping the disease at bay and warding off heart failure. When clinical signs of heart failure are present, it is often too late to treat.

Most dogs with congestive heart failure die because of the disease within 6 months. In the most severe cases, dogs may only survive a few weeks to a few months. On occasion, some dogs may live for 1-2 years. If treated early – before heart failure occurs – dogs can live a relatively normal life, though it may be shorter than normal.

Certain breeds react differently to DCM. For example, the prognosis for Doberman Pinschers with DCM is less favorable than in other breeds, while DCM in Cocker Spaniels may be relatively slow to progress. In the end, each case of DCM is different.

What you can do is make sure to take your dog to the vet at any sign of laboring breath or exhaustion. Catching the disease early may allow you to help your pet live a longer and more comfortable life than if the disease isn’t diagnosed until heart failure is already present.

Living with DCM

Once your dog has been diagnosed with DCM, your main goal should be to ensure your dog is as comfortable as possible, and closely monitor his condition for changes in behavior. Your veterinarian will most likely recommend checkup appointments every 3-6 months, depending on what stage of advancement the disease is in.

If your dog is on medication to treat DCM, you will likely return to the vet every 10-14 days for a blood test to check the kidney and liver function, gauge your dog’s blood pressure and/or re-evaluate his heart beat. Of course, if you notice any advance in symptoms – like your dog having trouble breathing – don’t wait for the next scheduled appointment, make an emergency appointment with your vet, or if need be, an emergency vet clinic.

Another way you can help with your dog’s treatment is to monitor and record his breathing and sleeping patterns. This will help your vet determine when and if to adjust your dog’s medication accordingly.

If your dog has more advanced DCM that includes heart failure and/or abnormal heartbeats

Your veterinarian will recommend a recheck appointment every 2-4 months, and regular checkups and testing every 10-14 days to have a blood tests performed to check the kidney and liver values, and take your dog’s blood pressure. Make sure that you can monitor your dog consistently, it will give him the best chance at an extended life.

Get the Most Out of Your Time with Your Dog

DCM, unfortunately, is eventually fatal. But a diagnosis can give you a chance to realize what a gift your dog has been in your life, and push you to focus on enjoying the relationship you share with him every day. Being diagnosed with DCM does not mean your dog will pass away immediately. He may live for years with the right treatment and care.

Regardless of how much time he has left, make every day, every hour, and every minute count. Spend time with your dog doing the things you love to do together – sitting at the beach, taking a snooze on the couch or a short walk around the block. Your dog looks to you for love and reassurance. Give him both.

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