Dilated Cardiomyopathy

What Is Dilated Cardiomyopathy & What Causes It?

DCM causes your ventricles to grow larger, and the walls to thin and stretch. This in turn, makes it difficult for your heart to pump blood as forcefully as needed. In DCM, your heart is unable to move blood around your body effectively, potentially leading to serious complications. 

Typically, you’ll see signs of DCM beginning in your heart’s left ventricle (the main pumping chamber) and then progressing to affect other areas of your heart.

There are many causes of dilated cardiomyopathy. Information presented here is primarily about the genetic (inherited) form of DCM. 

Established causes of DCM include:

• Genetic (inherited) DCM
• Alcohol dependence
• Illicit drug use, like cocaine and amphetamines
• Some chemotherapy medications
• Infections
• Complications in late-stage pregnancy or shortly after childbirth
• Diabetes
• Obesity
• Thyroid disease
• Exposure to toxins like lead, mercury and cobalt
• Excessive iron in heart and/or organs (hemochromatosis)
• High blood pressure (hypertension)
• Untreated arrhythmias like atrial fibrillation
• Heart valve diseases like mitral valve or aortic valve regurgitation

Your service will be alert to the possibility of DCM if risk factors for the condition are present, like:

• Long-term alcohol and/or illicit drug use
• Long-term high blood pressure
• Neuromuscular disorders, like muscular dystrophy
• Other conditions known to be associated with heart muscle and heart valve damage such as haemochromatosis and autoimmune disease

Like other genetic heart diseases, the mutation that causes DCM can be inherited from parents or occur spontaneously at conception (this is known as a ‘de novo’ mutation). DCM is typically an autosomal dominant disease, meaning if a parent has the genetic mutation, there is a 50% chance they will pass it onto their child. However the child acquires the genetic mutation (from a parent or as a de novo mutation), they are at risk of developing DCM from birth. Additionally, there is no way to reverse or change the mutation, or completely eliminate the possibility that they will develop DCM at some point in their lives. What can be done, though, is diagnosing the disease as early as possible to improve life expectancy and quality of life. 

Often, genetic testing can confirm that DCM is caused by a genetic mutation after a comprehensive evaluation for all the other causes. Even without confirming an exact cause, DCM can be diagnosed and then treated. However, being precise about the cause can make a big difference to how it is managed. Specific genetic (inherited) forms of DCM have specific treatments, and genetic testing is crucial in making an accurate diagnosis. 

How Genetic Testing Can Help

Ultimately, there is no substitute for genetic testing when confirming that your DCM is inherited. The accurate diagnosis and improved treatment plans are critical for giving you the best possible life expectancy and quality of life. 

Furthermore, genetic testing can remove the need for complex clinical evaluations for family members. This is because your diagnosis is a strong indicator that family members may also have DCM. Your results can therefore be enough evidence to have relatives complete genetic testing also, leading to earlier diagnoses if anyone else is affected. An early diagnosis can limit the strain your heart is put under for a better overall prognosis.

Do You Have Dilated Cardiomyopathy Symptoms or Complications?

Regardless of its cause, DCM can present with a number of symptoms including:

• Shortness of breath when active or lying down (dyspnea)
• Reduced ability to exercise
• Chronic fatigue
• Dizziness or lightheadedness, even fainting (syncope)
• Swelling in legs, ankles and feet (edema)
• Fast, fluttering or pounding heartbeats (palpitations)
• Chest pain or discomfort

Many individuals notice only some but not all of these symptoms first. Only a few individuals develop all of the above symptoms at the same time. However, like many other heart conditions you may be asymptomatic or the symptoms you have may be minor or confused for another condition. As a result, it is important to be vigilant and follow up any of the above symptoms. Even if none of these symptoms are present, if you have a family health history that suggests the possibility of DCM it is important to speak with your general practitioner or cardiologist and, if necessary, seek evaluation by a service to ensure that DCM is diagnosed early.

This is because untreated DCM can lead to potentially life-threatening complications, like:

• Arrhythmias, due to scarring (fibrosis) and weakness of the heart’s walls.
• Leaky heart valves (regurgitation), as the condition makes it harder for the valves to close, allowing blood to leak backwards in the heart.
• Blood clots, because blood can pool in any of the heart chambers. These can then enter the bloodstream (thromboembolism), blocking blood flow to organs, including the heart and brain, leading to serious irreversible organ damage like heart attacks and strokes.
• Heart failure, as the heart cannot sufficiently pump blood around the body.
• Sudden death from any of the above complications.

Acting quickly when you notice symptoms, no matter how small, can minimise the likelihood of these complications occurring. This is why a timely diagnosis is important.

How Is Dilated Cardiomyopathy Diagnosed?

The diagnosis of dilated cardiomyopathy ultimately hinges on ruling out other potential causes for the symptoms and finding evidence of dilation and reduced contraction ability of your left ventricle. Standard initial evaluation includes taking a history and examining you; family history can be overlooked initially as the priority is to ensure DCM is diagnosed and initial treatment started as soon as possible. However, once the diagnosis is made, the care of your family members can be very important as they too may be at risk of DCM — this is where a genetic diagnosis helps greatly.

Depending on your history and examination, a cardiologist may then recommend:

• A coronary angiography to look at the conditions of your blood vessels.
• Blood tests to determine your iron levels and look for indicators of conditions, like immune or thyroid diseases, that can cause DCM.
• An echocardiogram (echo) to examine your heart’s structure.
• An electrocardiogram (ECG) to check for abnormalities in your heart rate and rhythm.
• An exercise stress test to check your heart’s functioning as you exercise.

Some issues, like leaky heart valves (regurgitation), may indicate dilated cardiomyopathy but can also be evidence of other conditions, like connective tissue disorders. This is why thorough dilated cardiomyopathy diagnostic testing and investigation needs to be done to ensure a correct diagnosis, which then means you receive appropriate treatment. Additionally, being aware of your family health history can help your physician narrow down your diagnosis. 

How Can Genetic Testing Help?

Genetic testing plays a very important role where the underlying cause of your DCM is unexplained. This is similar to arrhythmogenic right ventricular cardiomyopathy (ARVC), where unexplained heart issues can be the sign of a serious heart condition that can only be confirmed through genetic testing. A blood or saliva sample can be analysed by a laboratory for mutations (spelling mistakes) in genes that are important for heart muscle growth and function. A service with expertise in inherited heart conditions can then interpret these results to determine if you have genetic (inherited) DCM.

Other types of DCM cannot be picked up by genetic testing. However, sometimes patients have more than one cause for their DCM. For example, there may be a mutation that silently increases the risk of genetic (inherited) DCM, and DCM only develops after diabetes or high blood pressure ‘unmasks’ the condition. The patient may even have been told that they developed DCM because of their diabetes. However, the careful evaluation of a cardiac service that understands genetic heart conditions can be crucial in making the diagnosis of an underlying mutation. Then, genetic testing can identify other individuals in the family who are also at risk and need long-term surveillance. 

In summary, genetic testing is a tool that should be routinely considered in the evaluation of patients with suspected DCM. It should, however, be conducted by a service that intimately understands that cardiac genetics is not always straightforward, from the variability between conditions to how serious they can be. This also includes knowing which tests to order and how to accurately interpret the results.

Is Dilated Cardiomyopathy in Your Family?

The inherited (genetic) form of DCM can be passed down in families. Therefore, there may be clues for your diagnosis hiding in your family tree. Consider your family members and if they have had a history of heart conditions or symptoms that may indicate DCM. Sudden, unexplained deaths, and younger people dying without a clear cause in a family raises suspicion of a genetic cause of death, particularly inherited heart disease. Because genetic testing was not widely available previously, unexplained deaths in the family were always a mystery. These deaths may have been recorded in medical records as a sudden unexplained death, or something more specific, like sudden arrhythmic death syndrome, rather than specifically as a result of DCM or other inherited heart condition like Long QT syndrome, CPVT or hypertrophic cardiomyopathy. Now, with advanced genetic testing and expert services dedicated to inherited heart disease, a diagnosis can be made in such families. This is powerful information for families to understand the reason behind heartbreaking loss and a diagnosis can then protect living relatives from suffering the same fate.