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 survive 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. Your child needs to see a 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:

  • 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.

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

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

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, they may get oxygen or be placed 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. A heart transplant is another option. But it can be very difficult to find a donor heart for a baby. Also, the child will need to take medicines for the rest of their life to prevent rejection.

Surgery typically involves at least a series of several surgeries. In this very complex treatment, the surgeon redirects blood flow to the lungs and the body through several connections. The surgery is done in stages. The first surgery is done shortly after birth. The second stage is done between ages 4 to 6 months, and the third stage is done between ages 18 months and 3 years. 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 pediatric intensive care unit (PICU) to be closely watched. After the first surgery, you can expect your child to be in the hospital for several weeks. When your child is well enough to go home, they will most likely require oral medicines such as diuretics. In addition, your baby may require assistance with feeding using a feeding tube. 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.

Typically, after the first surgery, your baby will need frequent monitoring even when home. This may involve frequent phone calls with the medical team, daily checks of your baby's oxygen levels, and daily weights. Many centers have specialized programs that help families and train them in how to care for the baby at home. If any special treatments are to be given at home, the nursing staff will make sure that you or a home health agency is 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?

A baby with hypoplastic left heart syndrome needs surgery to survive.

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 may have physical developmental delays and will likely need extra support. Some children will need a heart transplant to survive into adulthood. They will also need regular follow-up care at a center specializing in this type of congenital heart care.

In the long term, children with HLHS 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 often have lower exercise tolerance.

Discuss your child's specific outlook with the 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 need surgery to survive.

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

  • After the surgeries, children will need special care and to 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.

Online Medical Reviewer: Dan Brennan MD
Online Medical Reviewer: Scott Aydin MD
Online Medical Reviewer: Stacey Wojcik MBA BSN RN
Date Last Reviewed: 8/1/2023
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