Hypoplastic Left Heart Syndrome (HLHS)

What is hypoplastic left heart syndrome?

Hypoplastic left heart syndrome (HLHS) is a spectrum of heart diseases in which the left-heart structures are underdeveloped. These structures include the mitral valve, the left ventricle, the aortic valve, and the aorta. HLHS is a congenital heart defect that begins during pregnancy. The cause of HLHS is unclear, and there are no known risk factors for this disease. It is not preventable.

What causes hypoplastic left heart syndrome?

HLHS is the result of under-development of sections of the fetal heart during the first eight weeks of pregnancy.

The cause of HLHS is complex and involves many factors. In some families, there is a genetic predisposition or tendency towards developing HLHS, but most families have no prior history of congenital heart disease. HLHS comes in many different forms. Some patients have a primary problem with their left ventricular heart muscle, some with the aortic valve, and some with the mitral valve. Many have problems with all three. These details matter to us at Boston Children’s Hospital and we customize the care to meet your baby’s needs.

What are the symptoms of hypoplastic left heart syndrome?

In most cases, children born with hypoplastic left heart syndrome (HLHS) appear healthy.

When a baby is not diagnosed during pregnancy, symptoms may develop within the first few hours or days of life:

  • rapid breathing or shortness of breath
  • rapid heartbeat or pounding heart
  • poor suckling and feeding
  • cold extremities (poor perfusion)
  • blue color of the skin, lips and nailbeds (cyanosis)
  • weakness

How we care for HLHS

At Boston Children’s Hospital, we have a team of specialists ready to evaluate your baby starting in the Advanced Fetal Care Center. This team includes cardiologists who specialize in fetal assessments, and a team of nurses and other specialists who will make sure your baby is in the best possible condition when born and will help you plan for every step along the way. In some babies, we are able to offer a fetal cardiac intervention even before the baby is born.

Boston Children’s heart surgeons treat a high volume of some of the most complex pediatric heart conditions in the world, with survival rates more than 98 percent. Our approach to treating HLHS is different for every child, based upon their individual needs. We are one of the few hospitals in the country to offer complex biventricular repair, an approach pioneered by Boston Children’s.

Our areas of innovation for HLHS

The Boston Children’s Heart Center offers a unique combination of technical expertise, a state-of-the-art cardiac intensive care unit and a continuous drive towards innovation that allows us to help when others cannot. We are here to serve as a resource to you. Some of our innovations include:

  • The Stage I operation (or Norwood Procedure) was initially developed and first performed at Boston Children’s Hospital.
  • We were the first center to perform a successful fetal cardiac intervention and have done more fetal interventions for HLHS babies than any other center in the world.
  • In our Congenital Valve Program we have pioneered surgical techniques for repairing the tricuspid valve in babies with HLHS and tricuspid regurgitation.
  • In our Biventricular Repair Program, we have learned how to recruit (grow), the smaller ventricles to make two pumping chambers instead of one.