Children's Hospital Colorado

Hypoplastic Left Heart Syndrome (HLHS)

Pediatric hypoplastic left heart syndrome

Children with hypoplastic left heart syndrome (HLHS) have a small, underdeveloped left side of the heart. This may involve all or some parts of the left heart, including the aorta, aortic valve, left ventricle and mitral valve. The left side of the heart is so underdeveloped that it cannot pump enough blood to the body.

At Children's Hospital Colorado, experts in the Colorado Fetal Care Center and Heart Institute have decades of experience caring for patients with HLHS. If your baby is diagnosed before birth, experts in our Fetal Cardiology Program will design a care plan that is right for both mother and baby. We'll be with you every step of the way, from diagnosis and delivery to follow-up visits. After your baby's birth, experts in our Single Ventricle Care Program will provide lifelong care for your child to help them thrive.

Watch the video below to learn how Oliver's family found hope following a prenatal HLHS diagnosis:

What is hypoplastic left heart syndrome?

Hypoplastic left heart syndrome is a congenital heart defect, meaning kids are born with the disease. With this condition, the only way for blood to get to the body is if it can pass back through the heart from the left atrium to the right atrium and ventricle.

Then, the blood passes through the pulmonary artery and through a small hole called the ductus arteriosus that connects to the aorta. The ductus arteriosus is one of the heart structures that allow a baby's heart to function in the womb, but it starts to close very soon after birth. This prevents blood from flowing properly, which is why early diagnosis and treatment are so critical.

Who gets hypoplastic left heart syndrome?

Hypoplastic left heart syndrome is more common in boys than girls, although the reason is not known. About 8% of kids with congenital heart defects have hypoplastic left heart syndrome.

See why our outcomes make us one of the top heart hospitals
The Connection Journey
Giving hope a heartbeat

After a devastating diagnosis, there still can be hope. We connected a family just diagnosed with HLHS with a family who's been there — to answer questions, to shed light and to offer hope — from diagnosis to surgery to recovery.

Watch their stories

What are hypoplastic left heart syndrome symptoms?

Children with hypoplastic left heart syndrome develop a blue or gray tint to their skin. This condition is called cyanosis. The blue color can become more intense when an infant cries.

Other hypoplastic left heart syndrome symptoms to look for include:

  • Low or faint pulse
  • Trouble nursing and feeding
  • Fast breath or shortness of breath
  • Extreme tiredness
  • Loud heartbeat

How is hypoplastic left heart syndrome diagnosed?

In some cases, a child's HLHS will be diagnosed during a routine ultrasound exam before he or she is born. If your doctor suspects hypoplastic left heart syndrome, more tests will be needed to confirm the syndrome.

The most common test is an echocardiogram that lets pediatric cardiologists see the structure of the heart and how it is functioning.

Other cardiac tests include:

What are hypoplastic left heart syndrome treatment options?

At Children's Colorado's Heart Institute, our doctors are experts at identifying and treating HLHS.

Hypoplastic left heart syndrome treatment options include:


After your child is diagnosed, your pediatric heart cardiologist will start him or her on medicine that helps keep the natural passage (ductus arteriosus) between the aorta and pulmonary artery open. This medicine is called PGE-2. It allows oxygen-rich blood and blood that needs oxygen to mix inside a child's heart.


There are two options for surgery for children with hypoplastic left heart syndrome: a surgical repair or a heart transplant.

Surgical repair

HLHS repair takes a series of surgeries, usually three, that typically take place within the first four years of a child’s life.

The first surgery, called the Norwood procedure, is performed in the first week of life. This surgery allows the right ventricle to function as the pumping chamber to get blood to both the lungs and the body.

During the Norwood procedure, the pulmonary artery and aorta are combined to create one larger path for blood to get from the heart to the body. The heart wall between the left and right atria is removed to let oxygen-rich and oxygen-poor blood mix in the heart. An artificial tube is made between the heart and the lungs so blood can get to the lungs.

The second surgery, the Glenn procedure (sometimes called a bi-directional Glenn or the Hemi-Fontan), is usually performed between 4 and 6 months of age. This surgery redirects blood from the upper part of the body away from the heart and directly to the lungs.

The final surgery redirects the blood from the lower part of the body away from the heart directly to the lungs. This is called the Fontan procedure and is usually performed at 2-4 years of age.

Following this series of surgeries, most children can have normal lives. But like any child with a complex congenital heart abnormality, he or she will need to see a pediatric cardiologist for monitoring after the repairs.

Heart transplant

The second option for kids with hypoplastic left syndrome is a heart transplant. At Children's Colorado, we have been transplanting hearts for more than 20 years.

Rather than doing surgery to repair the existing heart, a heart transplant will replace the defective heart with a new one from a donor. Transplant patients will require lifelong medication and will be followed by a transplant cardiologist to monitor possible rejection of the new organ.

Learn more about our nationally ranked Heart Transplant Program.

Living with hypoplastic left heart syndrome

Children with hypoplastic left heart syndrome will need regular follow-up appointments with a pediatric cardiologist to monitor their health. Most children will need to take medication after surgery.

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