Dayton Children’s Hospital

Hypoplastic Left Heart Syndrome (HLHS)

What is hypoplastic left heart syndrome?


Babies diagnosed with hypoplastic left heart syndrome (HLHS) are born with a condition that affects normal blood flow through the heart. It is more common in boys than in girls. The exact cause is unknown.

In babies with HLHS, the left ventricle, the aorta and two heart valves (mitral and aortic) are not properly developed at birth. As a result, the left side of the heart is unable to send enough blood to the body, so the right side of the heart has to work harder. This extra workload can eventually cause the right side of the heart to fail.

left hypoplastic syndrome

Blood flow with left hypoplastic syndrome

Normal heart blood flow

Normal heart blood flow

How is HLHS diagnosed?

HLHS may be diagnosed during your pregnancy after abnormalities are seen on an ultrasound. Your doctor will use a fetal echocardiogram (an ultrasound of your baby’s heart) to take a closer look at your baby and confirm the diagnosis.

Babies with HLHS who are not diagnosed during pregnancy usually develop signs within a few days after birth. Your baby’s symptoms may include:

  • Difficulty breathing
  • Lethargy
  • Pounding heart
  • Rapid breathing
  • A gray or bluish skin color
  • Trouble feeding
  • Cold hands and feet

While examining your baby, your doctor will first listen for a heart murmur with a stethoscope and feel for the pulses in the extremities. If the doctor hears a heart murmur or if your baby is showing symptoms of HLHS, tests will be used to confirm the diagnosis. The most common test used is an echocardiogram (a painless test that uses sound waves to create a moving picture of the heart). Other tests may include a chest X-ray, an EKG or a heart catheterization.

How is HLHS treated?

Once a diagnosis has been made, your baby will be admitted to the newborn intensive care unit (NICU) and may need a breathing machine (ventilator) to help with breathing. A medicine called prostaglandin E1 may be given to help keep your baby’s blood circulating.

Soon after birth, your baby will need three surgical procedures, which will be explained to you in detail by your baby’s doctor:

  1. Norwood procedure (usually done within two weeks of birth)
  2. Bi-directional Glenn Shunt procedure (usually done between 4 and 6 months of age)
  3. Fontan procedure (usually done sometime between 18 months and 3 years of age)

How will HLHS affect my baby during and after surgery?

During surgery, your baby will be given general anesthesia, which means the baby will be comfortable and sleeping. After surgery, your baby will need to stay in a cardiac intensive care unit (CICU) for the first few days and may be connected to several tubes and wires to allow your baby’s doctor to best monitor the baby’s condition. Pain control will be used to make sure your baby is comfortable.

Most of the tubes and wires will be disconnected before your baby leaves the CICU, after which he or she will spend several more days in the hospital in a step down unit.

Surgery is not a cure for HLHS, so your baby will need continuous monitoring by a cardiologist and may continue to have complications.

In rare cases, a heart transplant may be needed. If your baby receives a new heart, your baby will need to take medicines for life to keep the body from rejecting the transplant.

Photo credit: Centers for Disease Control and Prevention, National Center on Birth Defects and Developmental Disabilities.


Contact us

Do you have questions about your pregnancy and wonder if our services could be of assistance? Patients may contact our nurse navigator through the email form below or at 844-542-4602 to discuss your unique situation and determine if the Fetal to Newborn Care Center is right for you.

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