Hypoplastic left heart syndrome (HLHS) is a rare heart defect. With this syndrome, structures on the left side of the heart, such as the aorta, aortic valve, left ventricle, and mitral valve, may be:

  • Too small
  • Absent
  • Poorly developed

Since the heart can’t work the right way, oxygen-rich blood flow to the body is lower. Your child will need medical care right away.

Heart Chambers and Valves
heart anatomy

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Blood Flow Through the Heart

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HLHS is present at birth. It is caused by a genetic defect. It is not known exactly why the heart does not develop normally.

Risk Factors

Factors that may raise your chance of having a child with HLHS are:

  • People in your family who have congenital heart defects
  • Prior pregnancy with fetal heart problems or miscarriage


Symptoms often appear within days after birth. Tell the doctor if your baby has:

  • Blue/gray skin color
  • Cool skin
  • Problems breathing
  • Fast heart beat
  • Sweaty, clammy skin
  • Poor feeding


You will be asked about your child's symptoms and health history. A physical exam will be done.

Pictures may be taken of your child's chest. This can be done with:


Talk with your doctor about the best plan for your child. Some defects are hard to treat. Your child may have:


Medicines are needed to keep blood flowing through the ductus arteriosus. The ductus arteriosus is a connection between the pulmonary artery and the aorta. It should close within a few days after birth. Keeping this passage open is a short term treatment. Other medicines may be used as well.


Surgery may be done to help the blood flow. This can be done through a reconstructive and shunting procedures. This is often done in stages:

  • After birth
  • 4-6 months of age
  • 2-4 years of age

Lifelong Monitoring

Your child will need to see a heart specialist regularly. Heart medicine will be needed throughout your child's life.


HLHS can’t be prevented.


American Heart Association

Family Doctor—American Academy of Family Physicians


Canadian Cardiovascular Society

Heart and Stroke Foundation of Canada


Hypoplastic left heart syndrome. EBSCO DynaMed Plus website. Available at: Updated September 11, 2017. Accessed June 29, 2018.

Single ventricle defects. American Heart Association website. Available at: Updated September 12, 2017. Accessed June 29, 2018.

Last reviewed May 2018 by Kari Kassir, MD  Last Updated: 6/29/2018