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Hypoplastic Left Heart Syndrome

What it is

Hypoplastic left heart syndrome (HLHS) is a very serious and uncommon birth defect. When HLHS occurs, one or more parts of the left side of the heart do not fully develop. The mitral valve, left ventricle, aorta and/or the aortic valve may be very underdeveloped. This means that the left side of the heart cannot pump blood to the body very well, so the right side of the heart has to pump blood both to the lungs and to the rest of the body.


Symptoms are not always immediately apparent, so HLHS may take a few days to diagnose after birth. However, according to the Mayo Clinic, babies with HLHS are usually seriously ill immediately at birth.

  • Grayish-blue skin (cyanosis)
  • Rapid, difficult breathing
  • Poor feeding
  • Cold hands and feet
  • Being unusually drowsy/inactive


Anti-depressants: Several studies have linked maternal use of anti-depressants to an increased risk of the infant being born with hypoplastic left heart syndrome and other congenital heart defects. This means infants whose mothers took certain anti-depressants just before or during pregnancy are more likely to develop HLHS than unexposed babies. For more information, click any of the drug names below. Anti-depressants include:

Painkillers: Research has indicated that babies exposed to opioid painkillers before birth may face a more than doubled risk of developing hypoplastic left heart syndrome. Such painkillers include:

  • Oxycodone
  • Codeine
  • Hydrocodone


Until surgery can be performed, a baby with hypoplastic left heart syndrome will receive treatment such as:

  • Medication to prevent closure of the connection between the right and left sides of the heart
  • Breathing assistance from a machine (ventilator)
  • Intravenous fluids
  • Atrial septostomy, a procedure that creates an opening between the heart’s upper chambers (not necessary for babies who also have an atrial septal defect)

HLHS is treated with a three-step surgical procedure or a heart transplant. Children may need additional surgeries later in life if complications develop. A person born with HLHS will need follow-up care with a heart doctor for his/her entire life.


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