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Hypoplastic Left Heart Syndrome (HLHS) is a rare and serious congenital heart defect, meaning a baby is born with it. In children with HLHS, the left side of the heart—the part responsible for pumping oxygen-rich blood to the rest of the body—is severely underdeveloped.
In a healthy heart, the left side does the heavy lifting, sending oxygenated blood out to nourish the body. With HLHS, structures such as the left ventricle, mitral valve, aortic valve, and aorta are too small or not fully formed, making it impossible for the heart to function normally on its own.
Hypoplastic Left Heart Syndrome (HLHS) is a rare and serious congenital heart defect, meaning a baby is born with it. In children with HLHS, the left side of the heart—the part responsible for pumping oxygen-rich blood to the rest of the body—is severely underdeveloped.
In a healthy heart, the left side does the heavy lifting, sending oxygenated blood out to nourish the body. With HLHS, structures such as the left ventricle, mitral valve, aortic valve, and aorta are too small or not fully formed, making it impossible for the heart to function normally on its own.
What is HLHS?
Hypoplastic Left Heart Syndrome (HLHS) is a rare and serious congenital heart defect, meaning a baby is born with it. In children with HLHS, the left side of the heart—the part responsible for pumping oxygen-rich blood to the rest of the body—is severely underdeveloped.
In a healthy heart, the left side does the heavy lifting, sending oxygenated blood out to nourish the body. With HLHS, structures such as the left ventricle, mitral valve, aortic valve, and aorta are too small or not fully formed, making it impossible for the heart to function normally on its own.
How does HLHS Affect the Body?
Because the left side of the heart cannot effectively pump blood, the body must rely on the right side of the heart to do all the work. This is not how the heart is designed to function long-term, which is why HLHS requires immediate and ongoing medical care after birth.
Without treatment, HLHS is fatal. With intervention, children can survive and grow—but the journey is complex and lifelong.
What Treatment Looks Like
Treatment for HLHS typically involves a series of three open-heart surgeries performed in stages during early childhood:
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Norwood Procedure (within the first week or two of life)
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Glenn Procedure (around 3–6 months of age)
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Fontan Procedure (around 2–4 years of age)
These surgeries don’t “fix” the heart but instead reroute blood flow to allow the body to receive oxygen-rich blood as efficiently as possible.
In some cases, a heart transplant may be needed.
Living with HLHS
Children with HLHS are incredibly strong, but they often face ongoing challenges, including:
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Feeding difficulties and growth delays
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Developmental delays
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Increased risk of infections
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The need for frequent medical monitoring and possible future interventions
Despite these challenges, many children with HLHS go on to develop personalities full of joy, resilience, and light—deeply impacting everyone around them.
Why Research Matters
For us, this isn’t just a cause—it’s deeply personal.
Our daughter, Graylee Jo, was born with Hypoplastic Left Heart Syndrome (HLHS). Like so many heart warriors, she fought through the early stages of life with a strength that still humbles us. She underwent the first steps of the HLHS journey and entered what’s known as the “interstage” period—the time between the Norwood and Glenn surgeries. It’s a fragile window, one where families are sent home to love, monitor, and protect their child while living with the constant awareness that things can change quickly.
Graylee Jo passed away at home unexpectedly during that interstage period.
There were no alarms loud enough, no warning signs clear enough, no research advanced enough to prevent the unimaginable from happening. And that is exactly why research matters.
Research has the power to change outcomes. It can improve monitoring methods for interstage babies, develop better tools for early detection of complications, and refine surgical techniques and aftercare so that more children not only survive—but thrive. It can give families more than hope; it can give them time, answers, and a different ending.
Right now, families like ours are navigating a diagnosis filled with unknowns. They are learning medical language overnight, trusting machines and numbers, and carrying the weight of bringing their child home knowing how delicate that time can be. They deserve more certainty. They deserve better systems of support. They deserve breakthroughs.
We believe Graylee Jo’s life matters. Her story matters. And through advancing research, her legacy can be part of something bigger—helping protect other children and sparing other families from this kind of loss.
Because no parent should have to wonder if more could have been done.
In honor of another brave heart, the Miracle Miley Research Fund at Duke Children’s is dedicated to advancing lifesaving research for children with congenital heart defects—learn more or support this work at www.tinyurl.com/miraclemiley.
Graylee Jo's Grace - Fighting CHD One Heart at a Time
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