Hypertrophic Cardiomyopathy (HCM)

Nemours Cardiac Center at Nemours/Alfred I. duPont Hospital for Children

1600 Rockland Road, Wilmington, DE 19803 | Get Map & Directions »

Children’s heart conditions can’t be prevented, but a lot can be done to improve their hearts at any age. Thanks to advanced technology and the pediatric heart experts at the Nemours Cardiac Center (based at Nemours/Alfred I. duPont Hospital for Children), most children with a heart problem can be quickly diagnosed and treated. At the Cardiac Center, we specialize in the treatment of heart problems, including cardiomyopathies and heart failure.

If your child’s been diagnosed with hypertrophic cardiomyopathy (or “HCM,” for short), we’re here to ease your concerns, answer your questions, and give your child the best possible chance for a healthy future.

What Is it?

Hypertrophic cardiomyopathy (HCM) in children is a genetic disorder of a child’s heart muscle. It results in thickening of one or both ventricles (the pumping chambers of the heart). In many cases, the thickened muscle may prevent blood from flowing out (called “hypertrophic obstructive cardiomyopathy”). More often, the heart muscle is thickened throughout the ventricle. This results in a stiff heart that’s unable to relax and fill with blood — this is called “diastolic dysfunction” because it’s an abnormality of “diastole,” the period of time in the heart beat when the heart is relaxing and filling with the blood that it will pump out during the next contraction.

The underlying abnormality seems to be related to poorly organized and scarred muscle fibers. As part of this disorganization, there’s a risk of abnormal heart rhythms (“arrhythmias”) in children with hypertrophic cardiomyopathy.

How Does the Heart Normally Work?

When your child has a congenital heart defect, there’s usually something wrong with the structure of the heart. In order to understand your child’s condition, it can help to know how the heart should work normally.
Learn More About Normal Cardiac Anatomy »

Nemours’ experts at KidsHealth.org also offer these helpful resources to help both you and your child understand how the heart works:

How & When Is It Diagnosed?

Most children don’t develop symptoms until later in the course of the disease. Hypertrophic cardiomyopathy (HCM) in children is usually diagnosed at first when a caregiver hears a murmur, or because other family members are identified with hypertrophic cardiomyopathy.

In some cases, children may have:
  • fainting
  • chest pain
  • difficulty breathing
  • an episode of sudden death

Usually, hypertrophic cardiomyopathy (HCM) in children can be diagnosed using an echocardiogram (or “echo”). An echo is a completely safe and painless test that uses ultrasound (sound waves) to build a series of pictures of the heart.

Children may need additional tests, including cardiac catheterization. Catheterization involves inserting a thin plastic, flexible tube (called a “catheter”) into an artery and vein that lead to the heart. Cardiac catheterization is done under sedation with local anesthesia or under general anesthesia, depending on your child’s age and condition.

We also may perform genetic testing to identify the specific genetic cause and determine the need to screen relatives. It’s also important to determine whether there’s a component of obstruction to blood flowing out of the ventricle because this may determine whether or not a child needs surgery.

Learn More
How & When Is It Treated?

Children with hypertrophic obstructive cardiomyopathy (that is, those with obstruction to the blood flow out of the ventricle) may benefit from a surgical procedure to relieve the obstruction. This procedure is called a “septal myectomy” and involves removing the thickened muscle from the area below the aortic valve (the valve between the heart and the main blood vessel leading out to the body). This area is where the obstruction usually occurs. Results from this surgery are excellent and usually significantly improve children’s symptoms.

In adults, there are catheter procedures that inject alcohol into the same area of thickened muscle to cause the muscle to thin. In general, this procedure hasn’t helped symptoms as much, and because of concerns about long-term effects, it isn’t recommended in children.

Because of the risk of cardiac arrhythmias and sudden death, some children may benefit from the implantation of an automated internal cardioverter/defibrillator (or “AICD”). An AICD is a small battery-operated device that’s usually implanted near the left collarbone. It can monitor the heart rhythm and can provide a shock to “restart” the heart when an arrhythmia occurs. However, AICDs aren’t beneficial in all children, and the decision to implant an AICD will depend on each individual child.

Heart transplantation is occasionally necessary in cases of hypertrophic cardiomyopathy where children have ongoing symptoms or the high risk of sudden death make other options inappropriate. Very rarely, children may need a ventricular assist device (or “VAD”) until they’re able to be transplanted. VADs are pumps that replace the function of the heart.

Learn More About Heart Failure, Heart Transplantation and Mechanical Circulatory Support »

How Will It Affect My Child Long Term?

To monitor the changes in their heart muscle, children with hypertrophic cardiomyopathy will need frequent echocardiogram tests and physician visits. Medications may also help treat some of the symptoms. And children may, occasionally, need repeat surgery to treat obstruction of blood flow.

When children need a ventricular assist device (VAD) to assist with the function of their heart, they’ll often have to stay in the hospital until a transplant becomes available. Children also need to be on blood thinners while being supported by the VAD. Most children can function excellently and enjoy a normal quality of life following a heart transplant, but they will need to take medications to prevent rejection of the new heart for the rest of their lives.

If your child has hypertrophic cardiomyopathy, know that at the Nemours Cardiac Center we’re here to give your child the very best, most comprehensive and compassionate care. Our goal is to guide your family, from start to finish, through your child’s heart disease journey — and to help your child live the healthiest, most fulfilling life possible.

Heart Murmurs

A heart murmur is an abnormal sound (like a blowing or whooshing) that’s usually detected by a doctor who’s listening to the heart with a stethoscope during a routine exam. Learn More »

Why Choose Us

From our outcomes to our family-centered care, find out all of the reasons why your child’s heart will be in good hands at the Nemours Cardiac Center. Learn More »

Make an Appointment

(800) 416-4441

Insurance We Accept »

Information for Patients

Outpatient Services and Inpatient Units: (302) 651-6660

After 5 p.m. and Weekends:

Cardiac Intensive Care Unit: (302) 651-6644
General Inpatient Unit, 2B: (302) 651-6690


+1 (302) 651-4993

Stories From the Heart

Meet children treated in the Nemours Cardiac Center who know what it’s like to live with a heart problem.

Read Their Inspiring Stories »