Hypoplastic Left Heart Syndrome (HLHS) | Diagnosis & Treatment

How is hypoplastic left heart syndrome (HLHS) diagnosed?

Most pregnant women have fetal ultrasounds during the course of their pregnancies. If a basic (level one or two) ultrasound shows the possibility of heart abnormalities, a more detailed cardiac ultrasound — fetal echocardiogram — can correctly diagnose your baby’s heart defect.

What happens when a baby is born with HLHS?

Most babies with HLHS appear healthy right after birth. If your baby was not diagnosed during pregnancy, it will become apparent within the first few hours to days that your baby has a heart defect. Some combination (not necessarily all) of the following medical tests are used to diagnose or evaluate HLHS:

Based on the results of these tests, your child’s doctors will determine the best approach to treatment.

What are the treatment options for HLHS?

Fetal cardiac intervention

A small number of babies with hypoplastic left heart syndrome may benefit from intervention before birth. Our highly trained cardiologists can use a needle or tiny balloon catheter to open abnormal heart valves or other obstructions. Learn more about the Fetal Cardiology Program.

Medical treatment after birth

If fetal intervention is not an option for your baby, treatments after birth will focus on stabilizing your baby and may include:

  • medication to keep the patent ductus arteriosus (PDA) open
  • intravenous fluids through a tube inserted into a vein
  • a feeding tube if your baby has difficulty feeding
  • breathing assistance provided by a ventilator to ensure adequate oxygen 
  • a balloon atrial septostomy procedure to create an opening in the wall between the upper chambers of the heart to improve mixing of oxygen-rich blood and oxygen-poor blood

Shortly after birth, your child’s care team will take images of your baby’s heart using an echocardiogram to see every detail of your baby’s heart — the way the blood flows, the size and function of the ventricles, and how well the valves work.


Your child will usually need a series of three operations. The goal of these surgeries is to enable the fully-functioning right ventricle to do the work normally done by two ventricles and to separate the oxygen-rich blood from the oxygen-poor blood.

Biventricular repair

In some cases, a baby’s single ventricle heart can be converted into two functioning ventricles (biventricular circulation) through our Complex Biventricular Repair Program. This may be an option for children with borderline HLHS. In some situations, this repair can be the initial procedure, but in others, a series of procedures may be used to recruit the small left ventricle before converting the heart to biventricular circulation.

Home monitoring between stages 1 and 2

During the period between stage 1 and stage 2 surgeries, your baby’s heart circulation requires extra monitoring to prevent complications. Our Home Monitoring Program will give you goals for your baby’s growth and oxygen saturation levels and provide monitoring equipment for your baby. You’ll also get information on when to call.

What is the long-term outlook for children with HLHS?

The long-term outlook for children with HLHS continues to improve. Your child’s ultimate lifespan and quality of life depends on many factors. Every year, medical advancements further extend and improve the quality of life for those born with HLHS.

Your care team will have an ongoing relationship with your family and can help you create a long-term care program for your baby. The team can also advise you and your child on daily life issues such as exercise, activity levels, and nutrition.