Hypoplastic Left Heart Syndrome

Written by Shannon Johnson | Published on July 16, 2012
Medically Reviewed by George Krucik, MD

Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is a birth defect. In HLHS, the left side of the heart is underdeveloped. This affects the blood flow through the heart.

In a normal heart, the right side pumps blood that needs oxygen to the lungs, and the left side pumps blood with oxygen to the body. In HLHS, the left side is not able to function. In the first few days after birth, the right side of the heart is able to pump blood to both the lungs and the body. This is possible because of openings between the two sides of the heart. However, these openings soon close. Then it is difficult for oxygen-rich blood to get to the body.

HLHS usually requires surgery or a transplant soon after birth. Up to four out of every 10,000 live births will result in infants with HLHS. (LPCH)

Causes of Hypoplastic Left Heart Syndrome

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 parts of the heart usually affected by HLHS are:

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

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

Symptoms of Hypoplastic Left Heart Syndrome

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

Common symptoms include

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

Diagnosis of Hypoplastic Left Heart Syndrome

Babies are given an initial examination upon birth to check for any problems not readily apparent. If the doctor notices any symptoms of hypoplastic left heart syndrome, he or she will usually have the infant seen by a baby heart doctor right away.

Heart murmurs are another physical sign that a child has HLHS. A heart murmur is an abnormal sound caused by the blood not flowing properly. The doctor can hear this with a stethoscope. In some cases, HLHS is diagnosed before birth while the mother is undergoing an ultrasound.

In addition, the following diagnostic tests may be used:

  • chest X-ray: This test uses radiation to create pictures of the heart.
  • electrocardiogram (ECG): This test measures the heart’s electrical activity. It will reveal if the heart is beating abnormally and will assist a doctor in determining if there is any heart muscle damage.
  • echocardiogram (echo): This test uses sound waves to create a visual image of the heart’s physical structure and functioning. The waves will create a moving picture of the heart and all its valves
  • heart magnetic resonance imaging (MRI): This test uses a magnetic field and radio waves to create images of the heart.

How Is Hypoplastic Left Heart Syndrome Treated?

Children born with HLHS are usually taken to the neonatal intensive care unit (NICU) right away. Oxygen therapy (ventilator or oxygen mask) will be applied immediately along with IV medications to assist the heart and lungs. There are two major types of surgery to correct the heart’s inability to pump oxygenated blood back into the body—staged heart reconstruction and heart transplants.

The reconstructive surgery is carried out in three stages: the first is right after birth, the next when your child is between two and six 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 the heart so blood can bypass the underdeveloped left side. The surgical stages are as follows:

Stage 1: The Norwood procedure involves reconstruction of the heart including reconstruction of the aorta by connecting it directly to the lower right part of the heart. After the surgery, your baby’s skin might still have a blue tinge. This is because oxygenated blood and nonoxygenated blood are still sharing space in the heart. However, your child’s overall survival odds will increase if he or she survives this stage of surgery (Mayo Clinic, 2010).

Stage 2: Glenn shunt: In this procedure, the doctor will begin to reroute the blood that needs oxygen directly to the lungs instead of through the heart.

Stage 3: The Fonstan procedure completes the rerouting of blood started in the second stage. At this point, the right chamber of the heart will only contain oxygen-rich blood and will be in charge of pumping this blood throughout the body. Blood needing oxygen will flow into the lungs and then into the right chamber.

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

The other surgical option is a heart transplant. If a heart transplant is conducted, antirejection medication will be needed for your child’s lifetime.

What Is the Long-Term Outlook?

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 over 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, these children have less physical strength than other children their age and are slower to develop.

It is recommended that you keep a detailed record of your baby’s medical history. This will be helpful to any doctor your child visits in the future. Be sure to keep a clear line of communication open with your child to express feelings and concerns. Other long-term effects include:

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