Children's Hospital Colorado

Hypoplastic Left Heart Syndrome (HLHS)

About 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.

Pediatric hypoplastic left heart syndrome is a congenital heart condition, 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 backward through the heart from the left atrium to the right atrium and ventricle, then 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. The ductus arteriosus normally starts to close very soon after birth. At the Colorado Fetal Care Center, prenatal ultrasound can identify a baby with HLHS as early as 14 weeks gestation. Babies identified to have HLHS require careful prenatal monitoring and preparation for a high-risk delivery. Our multidisciplinary team will design a plan that is right for mother and baby. After birth, children with hypoplastic left heart syndrome will need lifetime follow-up care by his or her cardiologist and medication to keep the ductus arteriosus open in order to survive.

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 conditions have hypoplastic left heart syndrome.

What are some 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

Learn why parents choose our nationally-ranked Heart Institute.

How is hypoplastic left heart syndrome diagnosed?

In some cases, a child's hypoplastic left heart syndrome 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 (ECHO) that lets cardiologists see the structure of the heart and how it is functioning.

Other tests include:

Helpful links

If you'd like to learn more about hypoplastic left heart syndrome, visit:

What are some hypoplastic left heart syndrome treatment options?

At Children's Hospital Colorado Colorado Heart Institute, our doctors are experts at identifying and treating hypoplastic left heart syndrome.

Hypoplastic left heart syndrome treatment options include:


After your child is diagnosed, your pediatric 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.

Repair takes a series of surgeries, usually three, that typically take place within the first three 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, which is usually performed between 4 and 6 months of age, 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 2-3 years of age.

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

Learn how the Complex Congenital Heart Disease and Development Clinic helps kids with hypoplastic left heart syndrome.

Heart Transplant

The second option for kids with hypoplastic left syndrome is a heart transplant. At Children’s Hospital Colorado, we have been transplanting hearts in children 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 renowned 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 his or her heart health. Most children will need to take medication after surgery.

Related Departments