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Pediatric Hypoplastic Left Heart Syndrome (HLHS)

Hypoplastic left heart syndrome (HLHS) is a combination of several abnormalities of the heart and great blood vessels. It is a congenital (present at birth) syndrome, meaning that the heart defects occur due to underdevelopment of sections of the fetal heart beginning during the first eight weeks of pregnancy. 

In the normal heart, oxygen-poor (blue) blood returns to the right atrium from the body, travels to the right ventricle, then is pumped through the pulmonary artery into the lungs where it receives oxygen. Oxygen-rich (red) blood returns to the left atrium from the lungs, passes into the left ventricle and then is pumped out to the body through the aorta.

In hypoplastic left heart syndrome, most of the structures on the left side of the heart are small and underdeveloped. The degree of underdevelopment differs from child to child. The structures affected usually include the following:

  • Mitral valve. The valve that controls blood flow between the left atrium and left ventricle in the heart.

  • Left ventricle. The lower left-hand chamber of the heart. It receives oxygen-rich (red) blood from the left atrium and pumps it into the aorta, which takes the blood to the body. The left ventricle must be strong and muscular in order to pump enough blood to the body to meet its requirements.

  • Aortic valve. The valve that regulates blood flow from the heart into the aorta.

  • Aorta. The largest artery in the body and the primary blood vessel leading from the heart to the body.

Anatomy of a heart with hypoplastic left heart syndrome

Perhaps the most critical defect in HLHS is the small, underdeveloped left ventricle. This chamber is normally very strong and muscular so it can pump blood to the body. When the chamber is small and poorly developed, it will not function effectively and cannot provide enough blood flow to meet the body's needs. For this reason, an infant with hypoplastic left heart syndrome will not live long without surgical intervention:

  • Hypoplastic left heart syndrome occurs in 2 to 3 out of every 10,000 live births or 1 in every 4,344 babies born in the U.S. each year. 

  • HLHS occurs slightly more often in boys than in girls.

View information about our surgical volumes and outcomes at Children's National Hospital.



Advanced Heart Surgery for Children: Early Primary Repair

At Children’s National, we plan treatments with your child’s long-term health in mind. If a newborn needs heart surgery, we intervene early and aggressively to correct defects. This way, the repair or reconstruction grows with your child and he or she benefits from a faster recovery. This approach is called early primary repair.

Many heart programs for children recommend waiting until a newborn is older before performing heart surgery. However, the longer we wait, the more health consequences a child may suffer. We perform surgery on infants so we can give them the best possible start in life:

  • More than two-thirds of cardiovascular surgeries we perform are on patients less than 1 year old
  • Half of those surgeries are on newborns less than 1 month old

Preventing Brain Injury During Heart Surgery: Our Approach

When children need open heart surgery, we often need to place them on a cardiopulmonary bypass machine. During the surgery, the bypass machine takes over the function of the lungs and heart. This can carry a risk of neurological damage.

At Children’s National, our team takes every step possible to protect your child’s brain development. In fact, we are considered a leader in this area. Our heart specialists use evidence-based protective measures and take all the necessary steps to ensure a successful surgery—for your child’s heart and brain.

Heart Surgery for Children: Family Resources

Our goal is to maximize the quality of our patients’ lives and ease the stress on families. Children’s National Heart Institute provides many family-centered services because we understand that when a child is ill, it affects the entire family.

    Heart Surgery: What to Expect Before and After Your Child’s Procedure 

    Our approach to care results in shorter lengths of stay for patients following surgery. For example, we use the smallest incisions possible and streamline our surgical process so it’s efficient and effective. We provide:

    • Preoperative diagnosis. We pinpoint your child’s exact condition. An accurate diagnosis is crucial in order to tailor a personalized treatment plan. Learn more about cardiac imaging.
    • Postoperative care and evaluation. After your child’s surgery:
      • Pediatric cardiac intensivists and cardiac critical care nurses and therapists provide the next stage of care in our Cardiac Intensive Care Unit.
      • After a Cardiac ICU stay, we transfer your child to a dedicated cardiac unit with specially trained cardiac physicians and advanced practice nurse practitioners.
      • During the recovery period, we perform tests to ensure the success of the procedure.
    • Next steps. If your child needs any type of post-surgery therapy or other care, we plan for that and discuss the next steps with you.

    Learn More About

    • Services for Families: Support services and helpful resources for families and patients
    • Amenities: Information about our facilities and services available during your child’s hospitalization

    Contact Us

    For more information, call us at 1-202-476-2811.



    Treatment Services

    Heart Surgery

    Our pediatric heart specialists have dedicated their careers to providing excellent heart care to patients with congenital heart defects and other cardiac conditions. Learn more about pediatric heart surgery.

    Children's Team

    Children's Team


    Yves d'Udekem

    Yves d'Udekem

    Division Chief, Cardiac Surgery
    Co-Director, Children's National Heart Institute
     Mary Donofrio

    Mary Donofrio

    Medical Director, Prenatal Cardiology Program
    Co-Director, Cardiac Neurodevelopmental Outcome Program
    Advanced Imaging Cardiologist
    Richard Jonas

    Richard Jonas

    Emeritus Chief, Cardiac Surgery
    Senior Investigator, Center for Neuroscience Research
    Can Yerebakan

    Can Yerebakan

    Associate Chief, Cardiac Surgery
    Director, HLHS Hybrid Program
    Director, Cardiovascular Surgery Fellowship Program
    Locations that Treat this Condition

    Locations that Treat this Condition

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    Our Stories

    Our Stories

    Ashely smiling

    Ashley's Story

    Between her premature birth and her medical issues including her critical HLHS heart condition, her parents, Ana Mercedes and Axel Vela, were told that Ashley was unlikely to survive.
    Cayden and Reagen as babies laying next to eachother sleeping

    Cayden's Story

    Cayden was born with a life-threatening complex congenital heart defect. Learn how the hybrid procedure for HLHS helped Cayden.



    Cardiac Surgery

    Our pediatric heart surgery team performs twice the number of surgeries of any other hospital in the region, with some of the best outcomes in the nation.

    Children's National Heart Institute

    Our expert pediatric heart team, including more than 40 subspecialties, offer advanced heart care and excellent outcomes for thousands of children every year.

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    Chip's Story

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    When Chip was born just three days after Christmas, his family was excited to welcome their new son into the world. But things immediately took a turn for the worse.

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