Hypoplastic Left Heart Syndrome (HLHS)

What is hypoplastic left heart syndrome (HLHS)?

Hypoplastic left heart syndrome (HLHS) is a severe congenital heart defect in which the left side of the heart is underdeveloped.

In a normal heart , 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).

Hypoplastic Left Heart Syndrome Illustration

In addition to the most common form of HLHS shown in the animation below, 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 animations below.

Learn more about HLHS from the experts at Children's Hospital of Philadelphia's Cardiac Center in this video series.

Signs and symptoms of HLHS

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

  • Blue or purple tint to lips, skin and nails (cyanosis)
  • Difficulty breathing
  • Difficulty feeding
  • Lethargy (sleepy or unresponsive)

Testing and diagnosis of HLHS

Often, hypoplastic left heart syndrome is diagnosed before birth, with fetal echocardiogram (ultrasound). Our Fetal Heart Program can help you 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:

  • Echocardiogram (also called "echo" or ultrasound): sound waves create an image of the heart
  • Electrocardiogram (ECG): a record of the electrical activity of the heart
  • Chest X-ray
  • Pulse oximetry: a noninvasive way to monitor the oxygen content of the blood
  • Cardiac catheterization: a thin tube is inserted into the heart through a vein and/or artery in either the leg or through the umbilicus ("belly button")
  • Cardiac MRI: a three-dimensional image shows the heart's abnormalities

Once at Children's Hospital of Philadelphia, your baby will need intravenous (IV) medicines, and possibly a ventilator for help with breathing. A team of dedicated cardiac critical care medicine specialists in our Evelyn and Daniel M. Tabas Cardiac Intensive Care Unit (CICU) will immediately begin procedures to help stabilize your baby.

Treatment for hypoplastic left heart syndrome

Hypoplastic left heart syndrome is most often fatal without early intervention. 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.

Hypoplastic left heart syndrome surgery

Typically, your child will require open heart surgery to re-direct the oxygen-rich ("red") blood and oxygen-poor ("blue") blood. After these operations:

  • The right side of the heart will do what is usually the job of the left side — pumping oxygenated blood to the body.
  • The deoxygenated blood will flow from the veins to the lungs without passing through the heart.

The series of three reconstructive operations to repair HLHS — the Norwood, Glenn and Fontan procedures — is known as " Staged Reconstruction ."

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.

Follow-up care

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, such as HLHS, 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. These complications can include lung, liver and gastrointestinal diseases. CHOP has a special program, the Single Ventricle Survivorship Clinic, part of the Fontan Rehabilitation, Wellness, Activity and Resilience Development (FORWARD) Program, specializing in the care of these patients and is researching improved treatments for them.

As a group, children with complex congenital heart defects who have had open heart surgery as infants are also at a higher risk for neurodevelopmental issues when compared to children without congenital heart defects. The Cardiac Center at CHOP created the Cardiac Kids Developmental Follow-up Program to provide evaluation, screening and clinical care for children with complex CHD 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 Children's Hospital of Philadelphia and the University of Pennsylvania, meets the unique needs of adults who were born with heart defects.

Reviewed by David J. Goldberg, MD

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