Hypoplastic Left Heart Syndrome (HLHS)

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Hypoplastic Left Heart Syndrome (HLHS)

Early Diagnosis and Expert Care for HLHS

Little girl and mom at Nemours to be checked for Hypoplastic Left Heart Syndrome.

Hypoplastic left heart syndrome (HLHS) is a heart defect where the left side of the heart doesn’t develop properly. This means it’s smaller and weaker, so the right side of the heart must work extra hard to pump blood to the rest of the body. 

At Nemours, we are experts at detecting heart problems early, including babies still in the womb — giving children the best chance. If your child is diagnosed with hypoplastic left heart syndrome, you can trust the pediatric heart specialists in our Nemours Cardiac Center.

Our board-certified, fellowship-trained pediatric cardiologists and cardiothoracic surgeons (specialists in surgical procedures of the chest, including the heart and lungs) are here to answer your questions, address your concerns, and offer treatment options, including hypoplastic left heart syndrome surgery. Our cardiac teams offer the latest in research-backed care, delivered with compassion.

In addition, we offer the Nemours app , which includes special features specifically for patients with HLHS and allows your child's cardiac care team to proactively monitor your child and potentially identify any emerging problems as quickly as possible. 

What Is Hypoplastic Left Heart Syndrome (HLHS)?

What Is Hypoplastic Left Heart Syndrome (HLHS)?

How a heart works

En español: Síndrome de corazón izquierdo hipoplásico  

Hypoplastic left heart syndrome (HLHS) is a rare birth defect of a baby's heart. The left side of the heart doesn't grow as it should, making it smaller and weaker than normal.

The left side of the heart is supposed to pump blood out to the body. But a baby's heart with HLHS can't do the job. This makes a baby very sick. Without medicines and a series of three surgeries to rebuild the heart, babies with HLHS won't survive.

The left side of the heart can't be fixed, so the goal of the surgeries is to rebuild parts of the heart and "redirect" the way blood flows to and from the body.

Soon after birth, a baby with HLHS needs around-the-clock care in a hospital for the first weeks or months of life.

How Does the Heart Work?

The heart is a muscle that pumps blood. It acts like two pumps in one. The pumps are called ventricles and each has an important job:

  • The right ventricle gets blood from the body and pumps it out the pulmonary artery to the lungs. In the lungs, blood fills up with oxygen and gets rid of carbon dioxide.
  • The left ventricle  gets the blood from the lungs and pumps it out through the aorta  to the body.

Because it pumps blood to the entire body, the left ventricle is a stronger pump than the right ventricle.

What Happens in Hypoplastic Left Heart Syndrome?

What Happens in Hypoplastic Left Heart Syndrome?

How a heart with HLHS pumps blood.

With hypoplastic left heart syndrome:

  • The left ventricle and aorta are too small to pump enough blood to the body.
  • The right ventricle, which is only supposed to pump blood to the lungs, pumps blood to the lungs and the body through an extra pathway called a patent ductus arteriosis (PDA) . That means the right ventricle gets overworked.
  • Babies with HLHS are almost always born with an atrial septal defect (ASD) . This is a hole in the upper part of the heart. It lets blood with oxygen mix with blood low on oxygen. Then the right ventricle pumps the blood to the lungs and the body.

What Are the Signs and Symptoms of Hypoplastic Left Heart Syndrome?

Within a few hours to a day or so after birth, a newborn with undiagnosed HLHS may have:

  • trouble breathing
  • blue or grayish coloring of the skin and nails
  • difficulty feeding
  • lethargy (very little activity)
  • weak pulses in the arms and legs
  • few wet diapers

What Causes Hypoplastic Left Heart Syndrome?

HLHS is a birth defect that happens when a baby is growing in the womb. No one knows exactly what causes it, but it could have a mix of causes, including a baby's genes (DNA) .

How Is Hypoplastic Left Heart Syndrome Diagnosed?

How Is Hypoplastic Left Heart Syndrome Diagnosed?

Hypoplastic left heart syndrome can be diagnosed with:

How Is Hypoplastic Left Heart Syndrome Treated?

HLHS is first treated with medicines, and then a series of three surgeries. Without surgery, a baby won't survive. Treatment for HLHS starts as soon as the baby is born.


Immediate treatment includes a medicine called prostaglandin. Prostaglandin keeps the PDA open so oxygen can get to the body.

Some babies need other medicines to help balance how much blood goes to the lungs and how much goes to the body.

Also if the ASD is too small, it might be made bigger. This is done with a cardiac catheterization   procedure or by surgery.

The Surgeries

Because the left ventricle and aorta are too small, the goals of the surgeries are to:

  • Use the right ventricle to pump oxygen to the body.
  • Send the blood coming back from the body straight to the lungs without having to pass through the heart.

Surgeries are done in stages as a baby grows. They are (in order):

  1. Norwood Procedure
  2. Glenn Procedure
  3. Fontan Procedure  

Looking Ahead

Being actively involved in your child's care plan can help you feel more in control.

Services We Offer for HLHS

Services We Offer for HLHS

The expert teams in our Nemours Cardiac Center locations offer a full range of pediatric heart care to diagnose and treat hypoplastic left heart syndrome. Services vary by specialist and location, but may include:

  • Fetal Diagnostics. Early detection in our perinatology and fetal medicine centers help us diagnose congenital heart defects and make a treatment plan for when your baby’s born. 
  • Cardiac Diagnostic Testing. State-of-the-art, noninvasive and minimally invasive tests for kids of all ages. 
  • Cardiology. Medicines are used to help manage oxygen and blood flow. 
  • Cardiac Catheterization. Most babies with HLHS are also born with an atrial septal defect (or “ASD”), but it might be repaired using a catheter (thin, flexible tube) to help relieve symptoms. 
  • Heart Surgery. Surgical repair for hypoplastic left heart syndrome will be done in a series that includes the Norwood, Glenn and Fontan procedures. 
  • The Nemours app . You can use the app to record vital statistics and provide videos of your child’s progress. The Nemours app is also our patient portal, and includes great features like: 
    • see appointment information
    • message your child's care team 
    • get test results
    • have video visits with your child's providers
Why Choose Us for HLHS Repair and Care

Why Choose Us for HLHS Repair and Care

Our Nemours Cardiac Center team has the experience to provide accurate, efficient diagnosis and treatment of hypoplastic left heart in children. World-class heart care requires the compassion to understand your family's journey, and the expertise to heal even the most complex conditions.

Our cardiac surgeons treat a vast array of heart defects in infants, children and teens, using the most innovative, up-to-date approaches. Our specialty is the early detection and repair of heart problems, so your child will have the best possible chance for a healthy future. 

Regional HLHS Highlights 

Services, programs, facilities and care teams differ at each location. Call for details.

Ranked in top children's hospitals for cardiac care.

We offer care for newborns and children with hypoplastic left heart syndrome at Nemours/Alfred I. duPont Hospital for Children (Wilmington, Del.) and select Nemours duPont Pediatrics locations.  

The Nemours Cardiac Center located at duPont Hospital for Children is ranked among the best children’s hospitals in the nation for pediatric cardiology and heart surgery by U.S. News and World Report.  

Our Palliative and Supportive Care Program located at duPont Hospital for Children in Delaware provides compassionate care for families and children coping with life-threatening or life-limiting conditions. 

We offer care for newborns and children with hypoplastic left heart syndrome at Nemours Children’s Hospital (Orlando) and select Nemours Children’s Specialty Care locations.  

Our renowned pediatric cardiology and cardiothoracic surgery team at the Nemours Cardiac Center in Central Florida offers inpatient, critical and surgical care at Nemours Children’s Hospital in Orlando — including dedicated cardiac anesthesiologists and state-of-the-art cardiac intensive care unit (CICU). 

They also have a dedicated program that offers skilled management of single-ventricle defects like hypoplastic left heart syndrome (HLHS). And since early detection means faster treatment, our Nemours Center for Fetal Care is available at multiple locations throughout Central Florida. 

We offer care for newborns and children with hypoplastic left heart syndrome at Nemours Children’s Specialty Care, Pensacola and our hospital affiliate, West Florida Healthcare, with outpatient and follow-up appointments also available at select Nemours Children’s Specialty Care locations.

Our Nemours Cardiac Center in Pensacola is home to one of the few accredited pediatric transthoracic and fetal echocardiography labs in Florida and, if needed, can facilitate the transfer of extremely ill children between our Nemours Cardiac Center locations (e.g., to Nemours Children’s Hospital).  

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