Hypoplastic left heart syndrome (HLHS) is a heart defect in which the left side of the heart is small and underdeveloped (hypoplastic). The left ventricle, mitral valve, aortic valve and aorta do not develop well, and the left side of the heart is unable to send enough blood with oxygen to the body. 

Symptoms may include:

  • Cool and pale feet and hands 
  • Difficulty breathing
  • Fast breathing
  • Poor feeding

HLHS is one of the most challenging and complex congenital heart diseases to treat and manage. Without treatment, this defect is usually fatal within the first weeks of life. The University of Maryland Children's Heart Program is highly experienced in diagnosing and surgically treating the hearts of babies born with HLHS.

Read our Patient Guidebook on HLHS

Our Patient Guidebooks provide additional information about the conditions we treat. They are not diagnoses and should never be used instead of medical advice.

HLHS – Causes and Diagnosis

HLHS is more common in males than in females but has no known cause. This condition is often diagnosed by fetal ultrasound before the baby is born, but may not be detected before birth. Those babies may initially appear healthy, although their oxygen levels will be slightly decreased.

If HLHS or another heart defect is suspected, the baby will be evaluated by a pediatric cardiologist.

This evaluation would include:

  • measuring the oxygen level
  • having an electrocardiogram (ECG)
  • having an echocardiogram (ultrasound of the heart)

Care Providers

Treating HLHS requires a team of highly trained providers. The University of Maryland Children's Heart Program team includes a pediatric cardiac surgeon, pediatric cardiologists, pediatric and neonatal intensive care doctors and nurses, pediatric cardiac anesthesiologists, cardiac operating room staff, cardiac nurses and many others with expertise in providing this complex and highly specialized care.

If HLHS is diagnosed while you are pregnant, you will see a maternal fetal medicine specialist who will treat you during your pregnancy. 

Treating HLHS

The immediate treatment for newborns with HLHS is to start the baby on an IV medication to keep the connection between the pulmonary artery and the aorta open. This allows the right ventricle to be the pump to both the lungs and the body. This treatment helps stabilize the baby for surgery, but does not provide a long-term solution.

Patients with HLHS must undergo the following three palliative surgeries within the first few years of their lives.

  • Norwood Operation – within the first week of birth
  • Glenn shunt procedure – between 4 and 6 months old
  • Fontan operation – between 2 and 4 years old.

HLHS patients will need continual cardiac care to monitor their condition. They will also require medication to prevent infections.

Contact Us

  • To learn more about Maternal Fetal Heart medicine, please call 410-328-3865.
  • To make an appointment with a Children's Heart Program physician, please call 410-328-4348.
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