New Hope for HLHS with Cord Blood

What is Hypoplastic Left Heart Syndrome?

Hypoplastic left heart syndrome (HLHS) is a rare, critical birth defect in which the left side of a baby’s heart doesn’t form correctly as it grows during pregnancy. When the left side of the heart is underdeveloped, it restricts normal blood flow to the body and the baby doesn’t get the oxygen within the blood that it needs.

HLHS is usually diagnosed through ultrasounds during pregnancy or after the baby is born. Babies born with HLHS need to undergo multiple open-heart surgeries or have a heart transplant to correct the defect, which is otherwise fatal. Although genetics could be a factor, the exact cause of HLHS is unknown so there is no way to prevent it.

Children with HLHS need medication and special lifelong follow-up care from a cardiologist. They’re also at risk for developing future health complications and may even need a heart transplant later in life if they haven’t had one already.

How Could Cord Blood Help?

Care for children with HLHS has come a long way, and researchers want to continue to improve it. New research studies are exploring how cord blood stem cells may help kids with HLHS. Cord blood contains the same powerful stem cells responsible for the development of organs, blood, tissue, and an immune system during pregnancy. They also have unique qualities able to heal and repair the body.

That’s why many researchers are now using cord blood in regenerative medicine research, in which stem cells have the potential to repair and replace tissue and organs damaged by disease, trauma, or aging.

It only makes sense that researchers want to harness the power and potential of cord blood. The hope is that using cord blood stem cells as a regenerative therapy will become an additional treatment for managing HLHS. This would give them the ability to grow new tissue in underdeveloped parts of the heart and strengthen the muscle to work more efficiently.

Cord Blood Use in HLHS Research Trials

The Mayo Clinic is proud to lead the first U.S. stem cell clinical trials for pediatric congenital heart disease.

They recently released results from a Phase I Clinical Study which determined it’s safe and feasible for children with HLHS to receive an injection of their own cord blood into their heart muscle during their second surgery, which is around 4-6 months of age.

“We want to see if these stem cells will increase the volume and strength of the heart muscle to give it greater durability and power to pump blood throughout the body,”

– Harold Burkhart, M.D., pediatric cardiovascular surgeon, OU Medicine in Oklahoma

This is a big first step in using cord blood as an alternative therapy for children with HLHS. Read the full results from the Phase I Clinical Study here.

Now a Phase II Clinical Study is underway. The study is taking place at seven hospitals across the country through the Mayo Clinic’s HLHS Consortium, and at this time, is only able to use cord blood units processed and stored at the Mayo Clinic. This study will further test the safety and take a closer look at the effectiveness of using cord blood to improve heart function in children with HLHS. Researchers are excited about these potential advancements, which may lead to children with HLHS leading longer, healthier lives.


A Study of Intramyocardial Injection of Autologous Umbilical Cord Blood Derived Mononuclear Cells During Surgical Repair of Hypoplastic Left Heart Syndrome (AutoCell-S2). (2019, October 31). Retrieved from

Congenital Heart Defects – Facts about Hypoplastic Left Heart Syndrome. (2019, November 12). Retrieved from

Hypoplastic left heart syndrome. (2018, August 4). Retrieved from

Mayo Clinic First in U.S. to Test Stem Cells for Cardiac Regeneration in Pediatric Congenital Heart Patients. (n.d.). Retrieved from

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