About hypoplastic left heart syndrome

Congenital heart defects are problems in the heart present at birth. One of the most complex and rare congenital heart conditions is hypoplastic left heart syndrome, a condition in which the left side of the heart is critically underdeveloped.

If your baby is born with hypoplastic left heart syndrome, the left side of the heart can’t effectively pump blood to the body, so the right side of the heart must pump blood both to the lungs and to the rest of the body.

Medication to prevent closure of the connection between the right and left sides, followed by either surgery or a heart transplant, is necessary to treat hypoplastic left heart syndrome. With advances in care, the outlook for babies born with hypoplastic left heart syndrome is better now than in the past.


Babies born with hypoplastic left heart syndrome usually are seriously ill immediately after birth. Signs and symptoms include:

  • Grayish-blue skin color
  • Rapid, difficult breathing
  • Poor feeding
  • Cold hands and feet
  • Being unusually drowsy or inactive

In a baby with hypoplastic left heart syndrome, if the natural connections between the heart’s left and right sides (foramen ovale and ductus arteriosus) are allowed to close, he or she may go into shock and may die. Signs of shock include:

  • Cool, clammy skin that may be pale or gray
  • A weak and rapid pulse
  • Abnormal breathing that may be either slow and shallow or very rapid
  • Dilated pupils
  • Lackluster eyes that seem to stare

A baby who is in shock may be conscious or unconscious. If you suspect your baby is in shock, immediately call 911 or your local emergency number.


Hypoplastic left heart syndrome occurs during fetal growth when the baby’s heart is developing. The cause is unknown. However, if your family has one child with hypoplastic left heart syndrome, the risk of having another with the same condition is increased. This may mean genetics plays a role in the development of hypoplastic left heart syndrome.

A normal heart has four chambers, two on the right and two on the left. In performing its basic job — pumping blood throughout the body — the heart uses its left and right sides for different tasks. The right side moves blood to the lungs. In the lungs, oxygen enriches the blood, which then circulates to the heart’s left side. The left side of the heart pumps blood into a large vessel called the aorta, which circulates the oxygen-rich blood to the rest of the body.

What happens in hypoplastic left heart syndrome
In hypoplastic left heart syndrome, the left side of the heart cannot properly supply blood to the body because the lower left chamber (left ventricle) is too small or in some cases it may not even exist. In addition, the valves on the left side of the heart (aortic valve and mitral valve) don’t work properly, and the main artery leaving the heart (aorta) is smaller than normal.

For the first several days of life, the right side of the heart can pump blood both to the lungs and to the rest of the body through a natural opening (foramen ovale) between the upper chambers of the heart (atria) or through a blood vessel that connects the pulmonary artery directly to the aorta (ductus arteriosus). When the foramen ovale and the ductus arteriosus are open, they are referred to as being “patent.”

If the ductus arteriosus and the foramen ovale close — which they normally do after the first day or two of life — the right side of the heart has no way to pump blood out to the body. However, many infants with hypoplastic left heart syndrome also have another heart defect, a hole in the wall between the upper chambers of the heart (atrial septal defect), that allows the right side of the heart to continue pumping blood to the body even if the ductus arteriosus or foramen ovale closes.

If you already have a child with hypoplastic left heart syndrome, you’re at a higher risk of having another baby with this condition than is a family who does not have a history of congenital heart defects.

Beyond family history, there are no clear risk factors for hypoplastic left heart syndrome.


Before birth
With advances in ultrasound technology, it’s possible for a baby to be diagnosed in utero with hypoplastic left heart syndrome before he or she is born. Doctors often can identify the condition on a routine ultrasound exam during pregnancy, sometimes as early as during the first trimester.

After birth
After your baby is born, his or her doctor may suspect a heart defect, such as hypoplastic left heart syndrome, if your baby has gray-blue skin or has trouble breathing. Your baby’s doctor may also suspect a heart defect if he or she hears a heart murmur — an abnormal whooshing sound caused by turbulent blood flow.

Doctors typically use an echocardiogram to diagnose hypoplastic left heart syndrome. This test uses high-pitched sound waves that bounce off your baby’s heart to produce moving images that can be viewed on a video screen. In a baby with hypoplastic left heart syndrome, the echocardiogram reveals a smaller than normal left ventricle and aorta. Because this test can track blood flow, it also shows blood moving from the right ventricle into the aorta (retrograde flow). In addition, an echocardiogram can identify associated heart defects, such as an atrial septal defect.


Without treatment, hypoplastic left heart syndrome is fatal, usually within the first few days of life.

With treatment, most babies — at least 75 percent — survive, although some may have the following complications later in life:

  • Tiring easily when participating in sports or other exercise
  • Heart rhythm abnormalities (arrhythmias)
  • Formation of blood clots that may lead to a pulmonary embolism or stroke
  • Developmental problems related to the brain and nervous system


Treatment for hypoplastic left heart syndrome involves either a three-step surgical procedure or a heart transplant. If the diagnosis has been made before the baby is born, doctors usually recommend delivery at a hospital with a cardiac surgery center. By itself, the condition doesn’t necessarily require delivery by Caesarean section.

Before surgery
Your baby’s doctor may recommend several options to help manage the condition before surgery or transplant. They include:

  • Medication. The medication prostaglandin helps dilate the blood vessels and keeps the ductus arteriosus open.
  • Breathing assistance. If your baby has trouble breathing, he or she may need help from a breathing machine (ventilator), which ensures adequate oxygen delivery.
  • Intravenous fluids. Your baby will receive fluids through a tube inserted into a vein.
  • Atrial septostomy. This procedure is used to create an opening between the heart’s upper chambers (atria) if the foramen ovale closes. If your baby has an atrial septal defect, an atrial septostomy may not be necessary.

Surgical options include a three-step surgical procedure designed to create normal blood flow in and out of the heart, allowing the body to receive the oxygen-rich blood it needs.

  • Step 1: A Norwood operation. This surgery is usually performed within the first two weeks of life. It involves reconstructing the aorta and connecting it directly to the heart’s lower right chamber (right ventricle). This allows the right ventricle to effectively pump blood to both the lungs and the body. After this operation, your baby’s skin will still have a blue cast because oxygen-rich and oxygen-poor blood continue to mix within the heart.
  • Step 2: A bi-directional Glenn or hemi-Fontan procedure. This procedure is typically performed around four to six months of age. It reduces the work of the right ventricle by allowing it to pump blood mainly to the aorta and allowing most of the blood returning from the body to flow directly into the lungs. After this operation, all the blood returning from the upper body is sent to the lungs, so blood with more oxygen is pumped to the aorta to supply organs and tissues throughout the body. Once your baby passes through this stage of treatment, the odds of survival are around 95 percent or greater.
  • Step 3: The Fontan procedure. This procedure is done between 18 months and 3 years of age. It allows the rest of the blood coming back from the body to go to the lungs. After this procedure, there’s no mixing of oxygen-rich and oxygen-poor blood in the heart, and your child’s skin will no longer look blue.

Another surgical option is a heart transplant, especially when the defects are complex. Babies with hypoplastic left heart syndrome can be considered for a transplant. While awaiting a heart transplant, your baby may require prostaglandin and other medications until a donor heart becomes available. However, transplantation is less used than repair because of the scarcity of donor hearts and the risk of dying while waiting for transplantation.

Follow-up care
After surgery or a transplant, your baby will need lifelong follow-up care with a heart doctor (cardiologist) who specializes in congenital heart disease, to monitor his or her heart health. Some medication may be necessary to regulate heart function. If your baby receives a heart transplant, anti-rejection medication will be necessary for the rest of his or her life to combat rejection of the new heart.

Your child’s cardiologist may recommend taking antibiotics before certain dental or other procedures to prevent infections, especially if the heart hasn’t been fully repaired yet or if there are small defects that remain after repair. In some cases, he or she may also recommend that your child limit physical activity.


There’s no known way to prevent hypoplastic left heart syndrome. If you have a family history of heart defects, or if you already have a child with a congenital heart defect, before getting pregnant consider talking with a genetic counselor and a cardiologist experienced in congenital heart defects.

Caring for a baby with a serious heart problem, such as hypoplastic left heart syndrome, can be challenging. Here are some strategies that may help make it easier:

  • Seek support. Ask for help from family members and friends. Talk with your child’s cardiologist about support groups and other types of assistance that are available near you.
  • Record your baby’s health history. You may want to write down your baby’s diagnosis, medications, surgery and other procedures and the dates they were performed, the name and phone number of your child’s cardiologist, and any other important information about your baby’s care. It’s also helpful to include a copy of the operative report from your child’s surgeon in your records. This information will help you recall the care your child has received, and it will be useful for doctors who are unfamiliar with your baby to review his or her health history.
  • Talk about your concerns. As your child grows, you may worry about activities in which he or she can safely participate. Talk with the cardiologist about which activities are best for your child. If some are off-limits, encourage your child in other pursuits rather than focusing on what he or she can’t do. If other issues about your child’s health concern you, discuss them with your child’s cardiologist, too.

Although every circumstance is different, remember that many children with congenital heart defects grow up to lead healthy, productive lives.