Hypoplastic Left Heart Syndrome (HLHS)

In hypoplastic left heart syndrome, the left side of the heart — including the aorta, aortic valve, left ventricle and mitral valve — is underdeveloped. Blood returning from the lungs must flow through an opening in the wall between the atria, called an atrial septal defect (ASD) or patent foramen ovale (PFO). The right ventricle pumps the blood into the pulmonary artery, and blood reaches the aorta through a patent ductus arteriosus (PDA). The baby often seems normal at birth but will need medical attention within a few days as the ductus closes.

This heart defect is usually fatal within the first days or months of life without treatment. It isn't correctable, but some babies can be treated with a series of operations or with a heart transplant.

Typical Heart

Heart with Hypoplastic Left Heart Syndrome

What Are the Symptoms of Hypoplastic Left Heart Syndrome?

Babies with this syndrome have:

  • Poor color and mottled skin
  • Rapid and difficult breathing
  • Difficulty feeding

How Is Hypoplastic Left Heart Syndrome Diagnosed?

Your baby may have been diagnosed while they were still in-utero, or before the birth, with a fetal ultrasound. If so, your obstetrician or maternal-fetal medicine specialist would have counseled you on the risks and develop and action plan for delivery. 

If the diagnosis is made postnatally, or after birth, symptoms develop that are similar to other disorders in newborn babies, such as a serious infection. Your baby may also have subtle physical features that suggest there is an underlying heart defect, but there may not be any abnormal heart murmurs. The diagnosis is confirmed with an echocardiogram.

How Is Hypoplastic Left Heart Syndrome Treated?

Early and prompt treatment is critical for the best outcome after birth because it is normal for a section of the heart called the patent ductus arteriosus (PDA) to begin to close and look quite ill. The PDA can be seen in the illustration above.

A medicine called prostaglandin will be given to your child until the first stage operation is performed. This medicine helps keep the heart structures open. A heart transplant is an option, but donor organs for infants are rare. Therefore, the most patients undergo three stages of surgical procedures, which are described below.

First Stage

After your baby is born, intravenous prostaglandin will be used to help provide a stable blood flow using your child’s patent ductus arteriosus for perfusion to the body and lungs. This medicine allows time for your team to take the images needed to help provide the best care for your child.

The first surgical procedure is done to help the right ventricle to pump blood to the body. There are three approaches (Hybrid, Norwood with a BTT shunt, or Sano with RV to PA conduit) based on your child’s anatomy, size and other circumstances. Your care team will discuss these options with you.

Typical Heart - Anterior 

Norwood - Hybrid

Norwood - BTT Shunt

Norwood - Sano Shunt

If your baby does not already have an existing hole between the upper chambers of the heart, called an atrial septal defect or ASD, an additional procedure is required to open the flow between the upper chambers.

The first stage of surgery often leads to the longest hospitalization of all three surgeries. It also requires the most intensive management after discharge. Instructions will be provided by your health care team in the Regenstein Cardiac Care Unit (CCU). The HeArT Clinic will help prepare you for this journey and make sure you have all the tools and resources during the interstage period and beyond.

Second Stage

The second stage is called a bi-directional Glenn, or hemi-Fontan operation, and consists of disconnecting the shunt to the pulmonary arteries and connecting the superior vena cava directly to the right pulmonary artery. With this, the heart volume is unloaded by directing blood flow from the upper body directly to the pulmonary artery. Your child is more stable in this state. Your child's care, including the interstage home monitoring program, is less intense in this stage. It is very common for infants to have similar oxygen saturations after the second-stage palliation as the first-stage palliation.

Typical Heart - Anterior 

Bidirectional Glenn

Third Stage

The third stage of the procedures is known as a Fontan operation. This consists of connecting the inferior vena cava to the right pulmonary artery. The result is that all the blood from the upper and lower half of the body drains to the pulmonary arteries and goes to the lungs (the blue blood no longer mixes with the red blood). The way that these connections are performed may vary from patient to patient.

The overall goals of the operation are to allow the right ventricle to pump only oxygenated blood to the body and to prevent or reduce mixing of the red and blue blood. Although the Fontan operation does not lead to a normal heart, it gives your child the best opportunity to lead a functional life.

At any time along your child’s pathway from stage 1, 2 or 3, there may be unplanned events. Concerns may arise that will require the team to perform additional tests or procedures. You and the care team will also need to reconsider the best roadmap of care for your child. For some children, transplantation will be the best option to maximize the quality of life. Your team will help guide your family based on your child's unique situation.

Treatment Risks

The risks of open-heart surgery always include bleeding, infection, neurological injury and the need for cardiopulmonary bypass.

Special risks of the stage 1, 2, and 3 surgeries are:

  • Narrowing of the aorta, shunt, and pulmonary artery
  • Injury to the nerve that supplies the vocal cord or diaphragm
  • Valve dysfunction
  • Ventricular function
  • Rhythm abnormalities

Our care team is trained to assess and quickly manage these issues if they occur.

Additionally, the pulmonary artery may become narrowed in the area that the BTT shunt, Glenn or Fontan shunts are sewn to the pulmonary artery. The aorta may have recurrent obstruction, and repair of the aorta carries the risk of injury to the nerve that controls one of the vocal cords.

What Are the Long-term Effects of Hypoplastic Left Heart Syndrome?

Left untreated, children with hypoplastic left heart syndrome usually die in early infancy. The long-term outlook is only beginning to be known, as this heart defect used to be fatal.

Virtually every child with this condition will require heart medicines. Depending on the success of surgery, individuals may lead functional lives for the rest of their days. Over time, the function of the right ventricle may worsen, and heart transplantation may be needed.

Children with hypoplastic left heart syndrome require lifelong follow-up appointments with a pediatric cardiologist and ultimately transition to an adult congenital heart disease specialist.

Problems encountered over time, or known morbidities include:

Interstage Home Monitoring (IHM) Program 

Research has shown that it is critically important to have an interstage home monitoring (IHM) program, that includes daily, at home assessments of oxygen saturations and weight between the stage 1 and stage 2 surgeries. Patients in an HMP are normally infants – the stage 2 repair, a Glenn, is typically performed between four- and six-months of age.

Daily home pulse oximeter checks alert the team of any sudden or changing patterns in the oxygenation. Daily weight checks tell parents and providers if a child is dehydrated, makes quick medical intervention possible, and decreases the rate of sudden death in this very fragile population of infants.

During this period, the primary caregiver at home, Single Ventricle Program APN, primary cardiologist and pediatrician will need to be in close communication regularly. This can be in the clinic and by phone. These frequent check-ins will help the care team catch any subtle changes in your baby’s health.

Parents have been instructed to call if any one of these red flags is seen at home:

  • Your child’s oxygen saturations change by:
    • Dropping consistently below 75%
    • Increase suddenly more than 90%
  • Your child is breathing harder, faster or is fussy.
  • Your child is unable to meet maintenance goal volume for 24 hours.
  • Your child is unable to attain goal to grow volume/24h for more than three days.
  • Your child does not gain .02 Kg or 20 grams over a 3-day span.
  • Your child loses .03kg or 30 grams or more over a 2–3 day span.
  • Your child has a temperature of 100.5 or greater.
  • You have any other questions or concerns.

Questions & Concerns

If you have any questions or concerns after your child is discharged, our team is available to take your call.

Mondays through Fridays, 8 a.m.-4 p.m., call the single ventricle nurse practitioner at 312.227.4000 and ask for Michelle Steltzer, CPNP-AC/PC.

Mondays through Fridays after 4 p.m. and on weekends, call the hospital operator at 312.227.4000 and ask for the cardiology fellow on call.

Heart Center Family Resource Guide

To help prepare families for their care with Lurie Children's Heart Center, we have compiled a list of resources about treatment and recovery. Learn how to get ready for an inpatient stay or outpatient visit, and read about our support services for patients and families.