Hypoplastic Left Heart Syndrome (HLHS) in Children

What is hypoplastic left heart syndrome in children?

Hypoplastic left heart syndrome (HLHS) is a group of defects of the heart and large blood vessels. A child is born with this condition (congenital heart defect). It occurs when part of the heart doesn't develop as it should during the first 8 weeks of pregnancy.

In HLHS, most of the left side of the heart is small, underdeveloped, or both. The following structures are usually affected:

  • Mitral valve. This valve controls blood flow between the left atrium and left ventricle.

  • Left ventricle. This is the lower left chamber of the heart. It pumps blood to the body.

  • Aortic valve. This valve controls blood flow from the left ventricle into the aorta, and then to the body. The aorta is the major blood vessel that delivers blood to the body.

  • Aorta. This is the large artery leading from the left ventricle to the body.

The left ventricle is normally very strong so it can pump blood to the body. When it is small and poorly developed, it can't pump any or enough blood out to the body. For this reason, a baby with HLHS will not live long without surgery to fix the defect.

What causes hypoplastic left heart syndrome in a child?

A child is born with this condition (congenital). Some congenital heart defects occur more often in certain families (genetic defects).

In many children, HLHS occurs by chance. There is no clear reason for its development.

What are the symptoms of hypoplastic left heart syndrome in a child?

Babies with hypoplastic left heart syndrome usually get symptoms shortly after birth:

  • Blue color of the skin, lips, and nails (cyanosis)

  • Pale skin

  • Sweaty, clammy, or cool skin

  • Trouble breathing

  • Fast heart rate

  • Cold feet

  • Poor pulses in the feet

  • Poor feeding

The symptoms of HLHS may look like other health conditions and heart problems. Have your child see his or her healthcare provider for a diagnosis.

How is hypoplastic left heart syndrome diagnosed in a child?

In many cases, hypoplastic left heart syndrome can be diagnosed with an ultrasound while the baby is still in the womb (uterus). After birth, you or your healthcare provider may notice that your baby seems limp or listless, has trouble breathing, or has a blue color to their skin, lips, or nails. Your child will need a pediatric cardiologist to make the diagnosis. This is a doctor with special training in treating heart problems in children.

The cardiologist will examine your baby, listen to their heart and lungs, and make other observations. Testing for congenital heart disease varies. Your child may have these tests:

  • Chest X-ray. A chest X-ray may show problems that show up with HLHS.

  • Electrocardiogram (ECG). An ECG records the electrical activity of the heart. It shows abnormal rhythms (arrhythmias), and finds heart muscle damage.

  • Echocardiogram (echo). An echo uses sound waves to make moving pictures of the heart and heart valves. Children with HLHS are almost always diagnosed by echocardiography.

How is hypoplastic left heart syndrome treated in a child?

Your baby will most likely be cared for in the neonatal intensive care unit (NICU). At first, he or she may be placed on oxygen, and possibly even on a ventilator. This is to help with breathing. Your child may get IV medicine . The medicine helps the heart and lungs work.

In most cases, surgery is used to treat hypoplastic left heart syndrome. Your baby’s cardiologist and cardiac surgeon will explain the risks and benefits. One treatment is a heart transplant. But it is very difficult to find a donor heart for a baby. For this reason, transplant is not often done as the first-line treatment.

Surgery typically involves a series of at least 3 surgeries. In this very complex treatment, the surgeon redirects blood flow to the lungs and the body with several connections. The surgery is done in stages. The first surgery is done shortly after birth. The second is done at about ages 3 to 6 months. The third is done at about ages18 months to age 4. Another option for treatment of HLHS is a combination of surgery and cardiac catheterization. This is called a hybrid procedure. It accomplishes the goal of the first surgery without the need for placing your child on a heart-lung machine. This procedure is typically reserved for children who are at high risk, such as prematurity, low birth weight, and organ dysfunction. 

After the surgery, your baby will return to the intensive care unit (ICU) to be closely watched. After the first surgery, you can expect your child to be in the hospital for 3 to 4 weeks. When your child is well enough to go home, the healthcare provider may recommend pain medicine, such as acetaminophen or ibuprofen, to keep your child comfortable. Your child's healthcare provider will discuss pain control before your baby goes home.

If any special treatments are to be given at home, the nursing staff will make sure that you or a home health agency are able to provide them.

You may get other instructions from your child's healthcare providers and the hospital staff.

How can I help my child live with hypoplastic left heart syndrome?

Without surgery, babies with hypoplastic left heart syndrome will not live longer than a few days or weeks.

The first stage of the surgery has the highest risk for complications and death. Some special treatment centers that do many of these procedures have higher survival rates than centers where fewer procedures are done. Survival rates are higher with the second and third stages of surgery.

Babies and children who have the staged surgeries will need special care and treatment to support growth and development. These children often have physical developmental delays and will likely need extra support.

In the long term, these children have an increased risk for complications such as heart failure and heart rhythm problems. They are also at risk for digestive and liver problems. Children with HLHS after surgery have lower exercise tolerance.

Some children will need a heart transplant to survive into adulthood.

Your child will need regular follow-up care at a center specializing in this type of congenital heart care.

Discuss your child's specific outlook with your healthcare provider.

When should I call my child's healthcare provider?

Call your child's healthcare provider if your child's symptoms get worse or if new symptoms develop.

Key points about hypoplastic left heart syndrome in children

  • Hypoplastic left heart syndrome is a group of problems that affect the heart and large blood vessels.

  • Babies usually get symptoms shortly after birth.

  • Babies with HLHS will not survive without surgery.

  • Most babies will need a series of at least 3 surgeries during their first 2 to 3 years of life.

  • After the surgeries, children will need special care and be monitored for complications.

Next steps

Tips to help you get the most from a visit to your child’s healthcare provider:

  • Know the reason for the visit and what you want to happen.

  • Before your visit, write down questions you want answered.

  • At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you for your child.

  • Know why a new medicine or treatment is prescribed and how it will help your child. Also know what the side effects are.

  • Ask if your child’s condition can be treated in other ways.

  • Know why a test or procedure is recommended and what the results could mean.

  • Know what to expect if your child does not take the medicine or have the test or procedure.

  • If your child has a follow-up appointment, write down the date, time, and purpose for that visit.

  • Know how you can contact your child’s provider after office hours. This is important if your child becomes ill and you have questions or need advice.