Hypoplastic Left Heart Syndrome

What is hypoplastic left heart syndrome?

Hypoplastic left heart syndrome is a birth defect of the heart. It means that several parts of the left side of a baby’s heart did not grow normally before birth:

  • The mitral valve, which normally separates the upper and lower left heart chambers, may be poorly developed, causing a problem called mitral stenosis. Or the mitral valve may not have formed at all—a problem called mitral atresia.
  • The lower left heart chamber (left ventricle) is poorly developed.
  • The valve from the left ventricle to the aorta (the aortic valve) is either extremely small (aortic stenosis) or did not form at all (aortic atresia). The aorta is the artery that normally carries blood from the left ventricle to the rest of your body,

The result of the poor development of the heart is that the left side of the heart does not work and cannot pump blood to the body.

How does it occur?

No one knows why the heart does not develop normally. However, if a family has 1 child with hypoplastic left heart syndrome, the risk that another child will have it is higher than normal. This may mean that genetics play a role.

What are the symptoms?

Babies with hypoplastic left heart syndrome may be in distress shortly after birth. They are usually gray or blue (cyanotic), feed poorly, and do not grow. They cannot survive without treatment.

How is it diagnosed?

An ultrasound will show that the structures normally on the left side of the heart are poorly formed. Rarely, cardiac catheterization is needed to confirm the diagnosis. Cardiac catheterization is a procedure in which a thin tube is passed through a blood vessel and into the heart to check the heart.

How is it treated?

Every baby is born with an open connection between the right and left sides of the heart. Normally this opening closes soon after birth. A baby with hypoplastic left heart syndrome will need medicine to stop this opening from closing until surgery can be done. The baby may also need a breathing machine to help with breathing. The baby will be given IV fluids.

Surgeries that may be done are:

  • Several open-heart operations to rebuild the heart during the first 2 or 3 years of life.
  • A heart transplant to replace the heart with a healthy donor heart. This surgery is done less often because of the shortage of donor hearts.

Another treatment option is to not treat the problem. Without treatment the baby will die peacefully during sleep within the first weeks after birth, generally without any suffering.

Parents of babies with hypoplastic left heart syndrome should discuss the treatment choices with their healthcare provider.

How long do the effects last?

Without treatment the baby will die, usually within the first few days after birth. With treatment, many babies survive and have a relatively normal life. They may tire more easily than other children and may need to limit physical activity. Some may have abnormal heart rhythms and a higher risk of blood clots that could cause problems such as stroke. Some children may have developmental problems.

Children who survive hypoplastic left heart syndrome with treatment will need to see a cardiologist regularly for the rest of their life. They may need to take medicine to control their heart rate and to help the heart pump better. They may need to take antibiotics before dental work and some other procedures to prevent infection of the heart.

Written by Reginald L. Washington, MD, FAAP, FACC.
Published by RelayHealth.
Last modified: 2009-08-23
Last reviewed: 2009-04-28
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
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