Cardiac Center

Hypoplastic Left Heart Syndrome (HLHS)

Before you begin reading about hypoplastic left heart syndrome (HLHS), please read the explanation of how the normal heart works for a basic understanding of its structure and function.

What is hypoplastic left heart syndrome (HLHS)?

Hypoplastic Left Heart Syndrome
View Large Hypoplastic Left Heart Syndrome Illustration
Hypoplastic left heart syndrome (HLHS) is a severe congenital heart defect in which the left side of the heart is underdeveloped.

The heart's left side has the job of pumping oxygenated blood into the aorta, the large artery that carries blood to the body. In a child with HLHS:

  • The mitral valve, which separates the two left chambers of the heart, is too small or completely closed (atretic).
  • The left ventricle (the lower, pumping chamber) is very small.
  • The aortic valve, which separates the left ventricle and the aorta, is too small or completely closed (atretic).

In addition to the most common form of HLHS shown in the above animation, there are a number of complex cardiac conditions with variations in the structures as described. In these children, where one ventricle is also small (sometimes called "HLHS variants," ) the treatment strategy is similar to those with the more typical HLHS, which is shown in the three animations below.


What are the symptoms of HLHS?

The following symptoms of hypoplastic left heart syndrome may be present at birth or several days later:


How is HLHS diagnosed?

Often, hypoplastic left heart syndrome is diagnosed before birth, with fetal echocardiogram (ultrasound). Our Fetal Heart Program will prepare a plan for delivery and care immediately after birth.

Sometimes HLHS is diagnosed hours or days after birth and the baby will need immediate therapy. Diagnosis of HLHS may require some or all of these tests:

Once at The Children's Hospital of Philadelphia, your baby will need intravenous (IV) medicines, and possibly a ventilator for help with breathing. Cardiologists and cardiac nurses in our Tabas Cardiac Intensive Care Unit (CICU) will immediately begin procedures to help stabilize your baby.


What are the treatment options?

Hypoplastic left heart syndrome (HLHS) is most often fatal without early intervention. It will typically require open-heart surgery to re-direct the oxygen-rich ("red") blood and oxygen-poor ("blue") blood in a series of three reconstructive operations known as "Staged Reconstruction."

Stage I – Norwood procedure


Stage I, known as the Norwood procedure, occurs within a few days of birth. The animation above shows Stage 1 of reconstruction of a heart with hypoplastic left heart syndrome. The shunt that is depicted is called a “Blalock-Taussig” shunt. Alternative types of shunts may be used based upon a child’s individual anatomy.

For a small number of children, alternative approaches to the Stage I Norwood procedure may be recommended, such as heart transplantation or a combination of surgery and catheter-based treatment called a “hybrid procedure.” Compared to 25 years ago, there are now many different options for treatment of this complex heart condition; an individualized approach is taken for each and every child. Your doctor will explain each individual option, and why one particular approach might be recommended for your child.

Stage II – Glenn procedure

Stage II, known as the bidirectional Glenn or the hemiFontan, typically occurs within four to six months of birth. The animation above shows Stage 2 of reconstruction of a heart with hypoplastic left heart syndrome.

Stage III – Fontan procedure

Stage III, known as the Fontan procedure, typically occurs between 1 1/2 to 4 years of age. The animation above shows Stage 3 of reconstruction of a heart with hypoplastic left heart syndrome using a technique called an “extracardiac Fontan.” The small hole intentionally placed to connect the conduit to the right atrium is called a “fenestration." In some children, a different modification, termed a “lateral tunnel fenestrated Fontan” is utilized. Your doctor will explain the differences and why one might be recommended for your child.

Frequent surveillance in infancy and early childhood is important to minimize risk factors for the eventual Fontan operation. Your child will also need a customized series of diagnostic tests between the planned stages of surgery, and throughout childhood. Additional surgical or catheter therapies, or in rare cases heart transplantation, may also be recommended.

After these operations:


What is the follow-up care for hypoplastic left heart syndrome?

Between the Norwood and Glenn operations

Though early outcomes for patients with single ventricle heart defects after staged reconstruction have improved dramatically, the period between the Norwood procedure and the Glenn operation remains a very vulnerable time for infants. CHOP created the Infant Single Ventricle Monitoring Program to focus on the care and monitoring of infants with single ventricle heart defects between the first and second reconstructive surgeries.

Through age 18

Children who have had surgical reconstruction for HLHS require life-long care by a cardiologist experienced in congenital heart disease. Sometimes they experience serious health problems. Many remain on medication, and additional surgeries may be required.

Patients with Fontan circulation are referred to as single ventricle patients. As these patients get older, doctors are recognizing that, while some do fine, many experience complications, including lung, liver and gastrointestinal diseases. CHOP has a special program, the Single Ventricle Survivorship Program, that specializes in the care of these patients, and is researching improved treatments for them.

In addition, as a group, children with complex congenital heart defects who have had open-heart surgery as infants are at a higher risk for neurodevelopmental issues when compared to children without congenital heart defects. The Cardiac Center at CHOP created the NeuroCardiac Care Program (NCCP) to provide evaluation, screening and clinical care for children with complex congenital heart disease who are at risk for neurodevelopmental problems.

Our pediatric cardiologists follow patients until they are young adults, coordinating care with the primary care physicians.

Into adulthood

We will help older patients with this condition transition to an adult cardiologist.

The Philadelphia Adult Congenital Heart Center, a joint program of The Children's Hospital of Philadelphia and the University of Pennsylvania, meets the unique needs of adults who were born with heart defects.


Contact us

Contact the Cardiac Center at The Children's Hospital of Philadelphia for a second opinion or for more information.

Reviewed by: David J. Goldberg, MD
Date: September 2013

  • Print
  • Share

Contact Us

For a second opinion, cardiac referral, or for more information.

To schedule an outpatient appointment.

Get Driving Directions

Protecting the Brain Before Birth

CHOP’s Fetal Neuroprotection and Neuroplasticity Program is investigating the link between congenital heart disease and brain development before birth. The goal of this research is to develop new prenatal therapies to improve long-term neurodevelopmental outcomes for children with CHD.

Single Ventricle Malformation Video

In this video, learn how experts diagnose and monitor single ventricle malformations before birth, allowing treatment to begin after delivery. Watch the Video.

HLHS Survival Stories

Meet our courageous patients and learn about their experience with HLHS and how the doctors at CHOP have helped them survive and thrive.