Hypoplastic Left Heart Syndrome (HLHS)
What is hypoplastic left heart syndrome?
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 hypoplastic left heart syndrome, most of the left side of the heart is small and
underdeveloped. These 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
- 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, an infant with hypoplastic left heart syndrome will not live long
without surgery to fix the defect.
What causes hypoplastic left heart syndrome?
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?
Babies with HLHS 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 hypoplastic left heart syndrome may look like other health conditions
and heart problems. Make sure your child sees his or her healthcare provider for a
How is hypoplastic left heart syndrome diagnosed?
In many cases, hypoplastic left heart syndrome can be diagnosed with an ultrasound
while the fetus 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 his or her skin, lips, or nails. Your child will need to see
a pediatric cardiologist for a diagnosis. This is a doctor with special training to
treat heart problems in children.
The cardiologist will examine your baby, listen to his or her 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 hypoplastic left heart syndrome.
- 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?
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 (delivered into a vein).
The medicine helps the heart and lungs work.
In the majority of cases, surgery is used to treat HLHS. 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 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 3 to 6 months of age. The third is done at about 18 months
to 4 years of age.
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 premature, low birth weight, and
After the surgery, babies 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
child 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
Living with hypoplastic left heart syndrome
Without surgery, most babies with HLHS 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
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 congenital
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
Key points about hypoplastic left heart syndrome
- Hypoplastic left heart syndrome is a group of problems that affect the heart and large
- Babies usually get symptoms shortly after birth.
- Babies with hypoplastic left heart syndrome will not survive without surgery.
- Most babies will need a series of 3 surgeries during their first 2 to 3 years of life.
- After the surgeries, children will need special care and be monitored for complications.
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.