New Parents

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What is HLHS?


Hypoplastic Left Heart Syndrome is a Congenital Heart Defect (CHD) where a child is born with a non-functioning left side of their heart.

This site helps explain in more detail how a HLHS heart functions and the surgical techniques in use today.
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The Foundation

Named after Micah Mason, a heart warrior, the Foundation was created to support institutions performing research of treatment of HLHS and similar CHDs.

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Research for the future of our Heart Warriors

Hypoplastic Left Heart Syndrome (HLHS) is a rare Congenital Heart Defect (CHD) that affects roughly 1% of children born with a CHD. In a child with a fully-formed heart, the right side of the heart receives blood from the body and pumps it to the lungs for oxygenation. Then the left side of the heart receives the blood from the lungs and pumps it out to the body. In a child with HLHS, the left side of the heart is too small to pump blood out to the body, and, within a few days after birth, the child's body becomes oxygen-starved and medical intervention is required to keep the child alive. Before the 1970s, no child with HLHS survived longer than a week.

In the 1970s and 1980s, surgeries were developed that re-worked the heart so that the right side of the heart could perform the function of both the left and right side of the heart. Since then the developments have produced a course of three surgeries that successfully re-tool the heart and have brought the survival rate of children born with HLHS to ~95%. This has been amazing for the children, of course, but now we need to consider their futures.

Now children with HLHS are living into adulthood. This brings questions with it: how long can a re-tooled heart do the work of a normal heart?; is there going to be degradation of the heart or a higher chance of outright failure?; can a body with a single-pass heart receive a donor heart in the event of failure, and how much work will be required in order to get the body to use a donor heart?

The Foundation is here to help people and organizations who are trying to answer these questions.

Foundation News

  • You are invited to a Zoom meeting. When: Jun 10, 2021 06:00 PM Central Time (US and Canada) Register in advance for this meeting:–urjssGNeo34j22pzrYSZxlspVsyPz After registering, you will receive a confirmation email containing information about joining the meeting.

  • Exciting News! The Micah Mason Foundation has formed a partnership with the Children’s Heart Foundation. This partnership establishes a fund in Micah’s name that is managed by the Children’s Heart Foundation. Once our funding goal of $100,000.00 is reached then the Micah Mason Foundation can choose to fund a research project that has been reviewed by the Children’s Heart Foundation. Please take a look at the following video to get a few more details behind why this is awesome! As part of this news, we will be holding a Research Reception in June to talk about and showcase research that has been funded and been successful in the past. Get on the list now by sending an email to Check out the new research fund here:;jsessionid=00000000.app20127a?fr_id=1200&pg=entry&NONCE_TOKEN=CA41B653B4E48A39C935D64979BD2423

  • The Micah Mason Foundation is participating in the 2021 DFW Congenital Heart Walk on August 21st 2021. Join our Team or Support our Walkers!

Heart Lock

Latest Videos

Resources for Parents

Research Reviews

Micah's Story

Our Journey with Micah

  • This is Micah, or Micah-man as we like to call him. He is the name-sake of the foundation. Born in 2015 with HLHS he has undergone two procedures known as the Norwood and Glenn surgeries to re-purpose the right side of his heart to function as his whole heart. He still has another surgery on the horizon, the Fontan surgery which will complete the re-purposing.

More of Micah's Story


Events that the Foundation is organizing


Projects the Foundation is work towards


News about the Foundation and about our heart warrior Micah