What Is Hypoplastic Left Heart Syndrome (HLHS)?

Hypoplastic left heart syndrome (HLHS) is a rare but serious birth defect. In HLHS, the left side of your child’s heart is underdeveloped. This affects the blood flow through their heart.

In a normal heart, the right side pumps blood that needs oxygen to the lungs, and then the left side pumps blood with fresh oxygen to the bodily tissues. In HLHS, the left side isn’t able to function. In the first few days after birth, the right side of the heart can pump blood to both the lungs and the body. This is possible because of a tunnel-like opening between the two sides of the heart called ductus arteriosus. However, this opening will soon close. Then, it becomes difficult for oxygen-rich blood to get to the body.

HLHS usually requires open-heart surgery or a heart transplant soon after birth. According to the Centers for Disease Control and Prevention (CDC), one out of every 4,344 babies born in the United States has this condition.

Since the birth defect occurs while your baby is still in the womb, most symptoms are apparent immediately after birth. Different areas of the left side of their heart are affected, so the symptoms will vary depending on the child.

The common symptoms of HLHS include:

  • a blue tinge to their skin, lips, and nails
  • a lack of appetite
  • drowsiness
  • inactivity
  • dilated pupils
  • a vacant stare
  • paleness
  • sweaty skin
  • mottled skin
  • heavy breathing
  • rapid breathing
  • an increased heart rate
  • cold hands and feet
  • a weak pulse

In most kids, HLHS is related to one of the following:

  • a genetic defect
  • abnormal chromosomes
  • exposure to an environmental toxin

Sometimes, HLHS occurs with no apparent cause.

The following parts of the heart are usually affected by HLHS:

  • The mitral valve controls blood flow between the upper left chamber, or left atrium, and lower left chamber, or left ventricle, of your child’s heart
  • The left ventricle is the lower left chamber of your child’s heart. It sends blood to their main artery, or aorta. Their main artery feeds oxygenated blood to the rest of their body. Underdevelopment of the left ventricle has a major effect on your child’s life because its strength directly relates to how effectively oxygenated blood flows through the rest of their body.
  • The aortic valve monitors the flow of blood from your child’s heart into their aorta.
  • The aorta is the biggest artery in your child’s body. It’s the primary blood vessel that leads from their heart to their body.

Babies with HLHS often also have an atrial septal defect. This is a hole between the upper left and upper right chambers of the heart.

You baby’s doctor will examine them when they’re born to check for any problems not readily apparent. If your child’s doctor notices any symptoms of HLHS, they’ll likely want a pediatric heart doctor to examine your baby right away.

Heart murmurs are another physical sign that your child has HLHS. A heart murmur is an abnormal sound caused by blood flowing improperly. You child’s doctor can hear this with a stethoscope. In some cases, HLHS is diagnosed before birth while the mother is undergoing an ultrasound.

The following diagnostic tests may be used as well:

  • A chest X-ray uses radiation to create pictures of your child’s heart.
  • An electrocardiogram measures the electrical activity in your child’s heart. It will reveal if their heart is beating abnormally, and it will help your child’s doctor learn if there’s any heart muscle damage.
  • An echocardiogram uses sound waves to create a visual image of the physical structure and functioning of your child’s heart. The waves will create a moving picture of their heart and all its valves
  • A heart MRI uses a magnetic field and radio waves to create images of your child’s heart.

Children born with HLHS are usually taken to the neonatal intensive care unit immediately after birth. Oxygen therapy, such as oxygen through a ventilator or oxygen mask, will be applied immediately along with intravenous, or IV, medications to assist their heart and lungs. There are two major types of surgery to correct their heart’s inability to pump oxygenated blood back into their body. They two major surgeries are staged heart reconstruction and a heart transplant.

Staged Heart Reconstruction

The reconstructive surgery is carried out in three stages. The first stage is right after birth, the next stage occurs when your child is between 2 and 6 months old, and the last one when your child is between 18 months and 4 years old. The end goal of the surgeries is to reconstruct their heart so blood can bypass the underdeveloped left side.

The following are the surgical stages of a heart reconstruction:

Stage 1: Norwood Procedure

During the Norwood procedure, your child’s doctor will reconstruct their heart, including their aorta, by connecting their aorta directly to the lower right part of their heart. After the surgery, your baby’s skin might still have a blue tinge. This is because oxygenated blood and deoxygenated blood are still sharing space in their heart. However, your child’s overall survival odds will increase if they survive this stage of surgery.

Stage 2: Glenn Shunt

In the second stage, your child’s doctor will begin to reroute the blood that needs oxygen directly to their lungs instead of through their heart. Your child’s doctor will reroute the blood using what’s called a Glenn shunt.

Stage 3: Fontan Procedure

During the Fontan procedure, your child’s doctor completes the rerouting of blood started in the second stage. At this point, the right chamber of your child’s heart will only contain oxygen-rich blood and will take charge of pumping this blood throughout their body. Blood that needs oxygen will flow into their lungs and then into the right chamber of their heart.

After Surgery

After a staged reconstruction, your baby will be closely monitored. Their heart is usually left open but covered with a sterile drape. This is to prevent compression by their rib cage. Several days later, when their heart has adjusted to its new circulation pattern, their chest will be closed.

If your child gets a heart transplant, they’ll need to take immunosuppressive medications to prevent rejection for the remainder of their lifetime.

Children with HLHS will require lifelong care. Without medical intervention in the first few days of life, most infants with HLHS will die. For most infants, the three-stage surgery is recommended instead of a heart transplant.

However, even after the surgeries, a transplant may be needed later in life. After surgery, your child will need special care and treatment. Very often, children with HLHS have less physical strength than other children their age and are slower to develop.

Other long-term effects may include:

  • tiring easily when exercising or playing sports
  • consistent heart rhythm problems
  • a fluid buildup in major parts of their body, including their lungs, stomach, legs, and feet
  • blood clots that could cause a stroke
  • abnormal development due to brain and nervous system issues
  • a need for follow-up surgeries

It’s recommended that you keep a detailed record of your child’s medical history. This will be helpful to any doctor your child visits in the future. Be sure to keep a clear line of open communication with your child so they can express their feelings and concerns.