• Heart disease is common in people living with Duchenne muscular dystrophy (DMD), which causes muscle weakness.
• In people with DMD, dilated cardiomyopathy (DCM) is the most common form of heart disease, in which the heart ventricles weaken, forcing the heart to work harder.
• Taking early action and sticking to a treatment plan can help extend a person’s life expectancy and improve their quality of life.

Duchenne muscular dystrophy is a rare neuromuscular disease that causes muscle weakness. The most common symptoms of DMD are muscle wasting (atrophy) and mobility issues. DMD also affects the heart muscle, increasing a person’s chances of developing heart disease.

Most people with DMD will develop heart disease at some point in their life. Fortunately, it can be managed with medications that help take stress off the heart. In this article, we’ll discuss how DMD and heart disease are related, along with how heart disease is diagnosed and managed.

How Does DMD Affect the Muscles?

People with DMD have a mutation (change) in their DMD gene, which provides the body with instructions for making the protein dystrophin. This protein typically works together with other proteins to give muscle fibers their strength, allowing them to contract (tighten) and relax. Specifically, dystrophin acts as an anchor to hold muscle cells together and protects them from being injured. It’s found in both the heart muscle and skeletal muscles that control movement.

In people with DMD, the dystrophin gene can’t provide the right instructions for making the protein. This means that muscle cells in the heart can’t make enough dystrophin. As a result, they can’t contract and relax properly, leading to heart disease and other DMD symptoms.

Heart Disease and DMD

The most common type of heart disease with DMD is dilated cardiomyopathy. To better understand how DCM develops, it’s important to learn about how the heart works.

The heart is made of four chambers — two top chambers known as atria and two bottom chambers known as ventricles. These chambers work together to pump oxygen-rich blood from the lungs to the rest of the body. Specifically, the left ventricle is the heart’s main pumping chamber.

In DCM, the ventricles begin to stretch out and become thinner, losing their ability to contract. As a result, the heart has a harder time pumping blood to the other organs. In people with DMD, the heart muscle is stretched and weakened because there isn’t enough dystrophin protein to hold the muscle cells together.

Eventually, the heart’s muscle cells are replaced by scar tissue (known as myocardial fibrosis), which makes it harder for the heart to pump blood properly. There may also be issues with sending electrical signals throughout the heart muscle to make it pump — these conduction issues lead to even more dysfunction.

How High Is the Risk of Heart Disease in DMD?

Since dystrophin is important for proper heart muscle function, nearly everyone with DMD will eventually develop heart disease. It can develop at any age, but symptoms typically appear at around 14 to 15 years old — by age 18, most people with DMD develop DCM.

Studies have also found that up to 70 percent of people with a milder form of DMD known as Becker muscular dystrophy have DCM. It tends to develop later in people with Becker muscular dystrophy compared to those with DMD — typically between the ages of 30 and 40.

Symptoms of DCM to look out for include:

• Fatigue
• Shortness of breath
• Swelling caused by fluid buildup in the feet and legs
• Palpitations (fast heartbeat)
• Arrhythmia (abnormal heartbeat)

DMD and Heart Failure

Left untreated, DMD can eventually lead to heart failure. This complication is diagnosed when the heart can no longer pump blood throughout the body, leading to worsening DCM symptoms. Be sure to talk to a health care provider doctor if you notice symptoms are getting worse as time goes on.

Heart failure is one of the most common causes of death for people living with DMD. By taking early action and getting the right treatment, you can improve your child or loved one’s quality of life and extend their life expectancy.

Diagnosing Heart Disease in DMD

Symptoms of dilated cardiomyopathy and heart failure that often lead to a diagnosis are usually noticeable when a person is walking or climbing stairs. These symptoms can be difficult to spot in people with DMD, however, because many of them have mobility issues that affect how they walk. Sometimes, by the time symptoms are noticeable, the heart disease has typically progressed and caused lasting damage.

It’s recommended that children with DMD have yearly follow-ups to check their cardiac function and look for abnormalities. Doctors use several imaging tests to measure how well their heart beats and pumps blood.

Electrocardiogram

An electrocardiogram (ECG or EKG) is a test that measures the electrical signals in the heart along with heart rate. It’s used to look for an abnormal heart rhythm caused by heart disease or heart failure.

During an ECG, a health care provider attaches 12 electrodes (sensors) to different areas of the chest and arms using sticky patches. The electrodes measure electrical signals sent through the heart muscle that tell it to beat. A computer reads the signals and displays them as waves that tell a doctor whether the heart is beating properly.

Echocardiogram

An echocardiogram measures how well blood flows through the heart. It uses sound waves or ultrasound technology to create pictures of the heart and valves (muscle flaps that control the direction of blood flow). Echocardiography measures how well the left ventricle pumps blood with each heartbeat — this is known as left ventricular ejection fraction (LVEF). A low LVEF measurement is often a sign of DCM.

During an echocardiogram, a health care professional who specializes in ultrasound places a wand or transducer onto the chest over the heart. The transducer sends sound waves into the body, which bounce off the heart and other structures. Those waves are used to create pictures of the heart and measure blood flow.

Cardiac Magnetic Resonance Imaging

One downside of echocardiograms is that they can’t always take clear pictures, especially in people with DMD. Instead, doctors may choose to use magnetic resonance imaging (MRI) technology. A cardiac MRI uses strong magnets and radio waves to take extremely detailed images of the heart.

Cardiac MRIs are the preferred imaging test for diagnosing heart disease and heart failure in people with DMD. This is because the test can provide more information on ventricular function than an echocardiogram.

Treating Heart Disease With DMD

If your child or loved one is diagnosed with heart disease, their doctor will create a treatment plan to help their heart stay healthy for as long as possible. There currently aren’t any medications specifically for treating DCM associated with DMD.

Instead, a doctor will prescribe commonly used heart disease treatments to take the extra stress off their heart. Most children with DMD start taking medications by around age 10 to help prevent disease progression, even if their test results are normal.

ACE inhibitors and angiotensin receptor blockers (ARBs) work by blocking the effects of the hormone angiotensin. These medications help relax blood vessels, making it easier for the heart to pump blood. ACE inhibitors are typically prescribed to people with DMD by the age of 10 or if there are early signs of myocardial fibrosis.

Other medications used to manage heart disease include beta-blockers, which help relax the heart muscle and slow the heart rate so it can beat more efficiently. Diuretics, including aldosterone antagonists, help remove extra fluid from the body to lower blood pressure.

Sticking to a DMD Treatment Plan

It’s also important that people stick to their DMD treatment plan. Common treatments include corticosteroids and exon-skipping therapies.

Many of the available exon-skipping therapies are currently being studied for treating cardiac dysfunction in DMD as well. These therapies help correct certain gene mutations to increase dystrophin levels. As a result, muscle cells in the heart could make more dystrophin to improve the symptoms of cardiac disease.

Talk With Others Who Understand

On myDMDcenter, people with Duchenne muscular dystrophy and their loved ones come together to gain a new understanding of DMD and share their stories with others who understand life with DMD.

Has your child or loved one with DMD been diagnosed with heart disease? Share your experiences in the comments below.