Hypoplastic Left Heart Syndrome (HLHS)

Hypoplastic left heart syndrome (HLHS) is a rare birth condition that affects the left side of the heart. It’s one of the most complex heart problems seen in newborns.

With HLHS, the heart’s left-sided valves (the aortic valve and the mitral valve) are either too small or didn’t form properly. In addition, the heart’s lower left chamber (ventricle), which is responsible for pumping blood out to the rest of the body, is often too small. So is the aorta, the main artery through which that blood normally flows. As a result of all of this, the heart can’t pump enough oxygenated blood to the body.

The baby’s heart often develops differently in a few other ways, too.

  • Babies with HLHS are often born with a hole between the left and right chambers of the heart, known as an atrial septal defect (ASD).
  • The blood vessel known as the ductus arteriosus, which connects the aorta and the pulmonary artery, usually remains connected after birth instead of going away. This condition is called patent ductus arteriosus (PDA).

These changes in the heart’s design allow at least some oxygen-rich blood to flow out to the body. However, the heart has to work much harder than it should.

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What Are the Signs and Symptoms of Hypoplastic Left Heart Syndrome?

HLHS is almost always detected before birth, or soon after a baby is born. Babies may have the following symptoms.

  • Bluish or grayish lips, skins and nails
  • Fast breathing
  • Trouble feeding
  • Poor weight gain
  • Low energy and activity
  • Fewer than normal wet diapers

At Connecticut Children’s, we can diagnose many congenital heart problems in utero before babies are even born. We work with our award-winning neonatologists, fetal cardiologists, the mother’s labor and delivery doctors, and our other pediatric specialists to plan ahead for the birth and the important moments that follow. 
 

What Causes Hypoplastic Left Heart Syndrome?

This condition occurs before birth, when a baby’s heart doesn’t develop properly during early pregnancy. There’s no one cause for this heart condition. For many babies, it’s passed down through a parent’s genes, and is linked to other genetic syndromes. For others, it may be caused by coming into contact with a certain chemical during pregnancy. Or it may be some combination of these causes.

How is Hypoplastic Left Heart Syndrome Treated?

Connecticut Children’s congenital cardiac surgeons specialize in complex techniques to correct HLHS, and are known for outstanding surgical outcomes.

  • Medication or a stent to keep the PDA open, so the right side of the heart can continue pumping some blood out to the body
  • Sometimes, cardiac catheterization to enlarge the hole between the heart’s upper chambers, allowing more oxygenated blood to flow from the left to the right side of the heart

Sometimes, patients take medication after surgery to help control how much blood goes to the lungs and body.

  • Staged reconstruction known as “single ventricle palliation”: Between birth and age 3, a series of three surgeries to rebuild the heart and redirect how blood flows through it
    • Norwood procedure: Allows the right ventricle to pump blood to the body
    • Glenn procedure: Connects a large vein to the pulmonary artery, allowing blood to flow directly to the lungs
    • Fontan procedure: Directs blood from the lower half of the body directly into the lungs to receive oxygen
  • Sometimes, surgery to enlarge the hole between the heart’s upper chambers, allowing more oxygenated blood to flow from the left to the right side of the heart
  • In extreme cases, heart transplant

After surgery, patients with HLHS should follow up with congenital heart experts who understand their unique anatomy. Connecticut Children’s provides this lifelong care, including advanced heart imaging close to home, and our nationally-accredited Adult Congenital Heart Disease program.