What is HLHS?

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 (stenotic) 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 (stenotic) or completely closed (atretic).
Structure of a Heart with Hypoplastic Left Heart Syndrome (Video)

In the animation above, doctors describe the structure of heart with HLHS

What are the 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)

How is HLHS diagnosed?

Often HLHS is diagnosed before birth, with fetal echocardiogram (ultrasound). Sometimes HLHS is diagnosed hours or days after birth and the baby will need immediate therapy. Diagnosis 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 - medical imaging
  • Pulse oximetry - a non-invasive 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 in the hospital, your baby will need intravenous (IV) medicines, and possibly a ventilator for help with breathing. Cardiologists and cardiac nurses will immediately begin procedures to help stabilize the infant.

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

Known as the Norwood procedure, this procedure usually occurs within a few days of birth. The video below 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.

Stage I (Norwood)

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, and 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

Known as the bidirectional Glenn or the hemiFontan, this operation typically is undertaken within four to six months of birth. The animation below shows Stage 2 of reconstruction of a heart with hypoplastic left heart syndrome.

Stage II (Glenn or hemiFontan)


Stage III: Fontan Procedure

Known as the Fontan procedure, this operation typically occurs between 1 1/2 to 4 years of age. The animation below showsStage 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.
Stage III (Fontan)
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:
  • 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.

What kind of follow-up care is needed? 

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.

Until approximately 25 years ago, infants with HLHS didn't survive.  As a result, we don't yet know the truly long-term effects of this condition.

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

Into adulthood

Older patients with this condition transition to an adult cardiologist. Some centers have programs to help with this transition.

Source: All of the above information and YouTube videos originate from The Children's Hospital of Philadelphia's Cardiac Center web page and are used with permission.