What is hypoplastic left heart syndrome in children?

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 eight weeks of pregnancy.

In HLHS, most of the left side of the heart is small, underdeveloped, or both. The following 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 the body. The aorta is the major blood vessel that delivers blood to the body. 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, a baby with HLHS will not live long without surgery to fix the defect.

What causes hypoplastic left heart syndrome in a child?

A child is born with this condition (congenital). 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.

How is hypoplastic left heart syndrome diagnosed in a child?

In many cases, hypoplastic left heart syndrome can be diagnosed with an ultrasound while the baby 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 their skin, lips, or nails. Your child will need a pediatric cardiologist to make the diagnosis. This is a doctor with special training in treating heart problems in children.

How is hypoplastic left heart syndrome treated in a child?

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. The medicine helps the heart and lungs work.

In most cases, surgery is used to treat hypoplastic left heart syndrome.

(Source: Stanford Children’s Health. https://www.stanfordchildrens.org/e)