Hypoplastic Left Heart Syndrome

What is Hypoplastic Left Heart Syndrome (HLHS)?

Babies born with hypoplastic left heart syndrome have an underdeveloped heart on the left side. This condition affects the way blood flows through the heart and to other parts of the body. The most common cause of HLHS is abnormal development of the left side of the heart during pregnancy.

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Signs & Symptoms

The most common signs and symptoms of hypoplastic left syndrome include:

  • Poor weight gain or growth
  • Sweating while eating, exercising, or crying
  • Tiring easily
  • Bluish color on skin, lips, and fingernails (cyanosis)
  • Rapid breathing or difficulty catching breath
  • Heart murmurs or abnormal heart sounds heart through a stethoscope
  • Poor blood circulation to other parts of the body
  • Irritability or fussiness
  • Poor feeding
  • Swelling in the legs, abdomen, or around eyes
  • Developmental delay

It is important to note that some newborns may not display any signs or symptoms of hypoplastic left heart syndrome at birth, but may appear later on.

Risk Factors

Risk factors for hypoplastic left heart syndrome include:

  • Genetic abnormalities
  • Maternal conditions
  • Diabetes or obesity during pregnancy
  • Premature birth
  • Exposure to certain medications or toxins during pregnancy
  • Race may be a factor in the higher incidence of hypoplastic left syndrome seen in Hispanic and African American populations
  • Maternal age
  • Multiple gestation pregnancy
  • Low socioeconomic status

Parents holding their baby boyDiagnosis

Hypoplastic Left Heart Syndrome is usually diagnosed by ultrasound during pregnancy or shortly after birth. Imaging studies such as echocardiography, MRI, CT scans, and X-rays may be used to confirm the diagnosis and assess the severity of the condition.

Laboratory tests may detect any associated genetic abnormalities or chromosomal anomalies.

A physician will conduct a thorough physical examination, including a review of the baby’s respiratory and cardiac function, to determine the presence of other underlying problems.

Genetic testing may be performed to confirm the diagnosis and additional tests may be necessary to assess the severity of the condition and determine a treatment plan.

A Three-Stage Approach to Surgery for Hypoplastic Left Heart Syndrome

  • The Norwood Procedure

A pediatric cardiothoracic surgeon can perform the Norwood procedure within days or weeks after a baby is born. 

This surgery allows the right ventricle to do the work of the left ventricle and pump blood into the body instead of toward the lungs.  

A new aorta is constructed from part of the pulmonary artery and directs both oxygenated and deoxygenated blood into the body. 

Additionally, a specialized pathway called a shunt is created to send blood directly to the lungs. 

This procedure acts as a temporary solution while babies gain strength and prepare for another surgery, typically performed at around six months of age.

  • Removing the Shunt

A second surgery, performed at around six months of age, removes the shunt and creates a direct pathway from the upper body to the lungs. 

The surgeon disconnects the superior vena cava, a large vein that carries blood from the head and arms to the heart, from the heart and attaching it directly to the pulmonary artery. 

The rerouting allows oxygenated blood to go straight into the lungs, giving the heart a rest by bypassing its delivery of blood to both body and lungs.

  • Fontan Procedure

Between 18 and 36 months of age, the Fontan procedure is performed in which the cardiothoracic surgeon disconnects the inferior vena cava, a large vein that carries deoxygenated blood from the legs and abdomen to the heart, and connects it to the pulmonary artery. 

Following the procedure, oxygen-depleted blood from the upper and lower body will now flow directly into the lungs. To help regulate overall blood flow, surgeons also create a small hole to allow for some of the blood to return to the heart.

Oxygenated blood is then pumped to the rest of the body through a single actively functioning ventricle in the heart.

A little girl holding her teddy bearPrevention

Hypoplastic Left Heart Syndrome cannot be prevented. However, women who are pregnant should attend regular checkups with their doctor and maintain a healthy lifestyle.

A detailed family history from both the mother and father can help a physician determine the risk of a cardiovascular defect.

Finally, some doctors may suggest prenatal testing such as ultrasound or echocardiography to identify potential abnormalities in fetal development.

CHRISTUS Children's - The Heart Center

CHRISTUS Children's specializes in pediatric care for infants, children and adolescents as well as maternal and fetal care for women with high-risk and routine pregnancies. From birth to age 18, CHRISTUS Children’s provides comprehensive, coordinated care from a team of pediatric and maternal experts.

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