Heart and Blood Conditions

Hypoplastic Left Heart Syndrome

What Is Hypoplastic Left Heart Syndrome?

Hypoplastic left heart syndrome is a rare and serious birth defect in which the left side of the heart is not fully developed.

In a healthy heart, oxygen-poor (blue) blood comes from the organs and tissues of the body into the right atrium (one of the  atria ) of the heart. Then it flows into the right  ventricle , which pumps it to the lungs.

Oxygen-rich (red) blood comes from the lungs into the left atrium. Then the  mitral valve  opens, allowing blood to flow from the left atrium into the left ventricle. Next the  aortic valve  opens, and the left ventricle pumps blood through the  aorta  and out to the organs and tissues of the body.

In hypoplastic left heart syndrome, the left ventricle is too small or not well developed, and the mitral and aortic valves are not there or are very small. The first portion of the aorta is also small. This means that the left heart cannot pump enough oxygen-rich blood to the body.

Hypoplastic Left Heart Syndrome in Children

Because the left ventricle cannot pump enough blood to the body, the right ventricle must do all the work. Oxygen-rich blood from the lungs and oxygen-poor blood from the body come to the right side of the heart. The right ventricle then pumps this mixed-oxygen (purple) blood to both the body and the lungs.

In a newborn, this can work for a short time because babies have an opening connecting their right and left atria (called the foramen ovale) and a blood vessel connecting their  pulmonary artery  to their aorta (called the ductus arteriosus). These connections normally close soon after birth.

If these structures close in a baby with hypoplastic left heart syndrome, little or no blood can flow through their heart and out to their body. So the most urgent issue for them is to maintain openings and make connections in the right places for blood to flow.

The other main health issue for babies with this syndrome is that their right ventricle must do so much work. Over time, hypoplastic left heart syndrome can cause heart failure .

About one in every 4,000 babies has hypoplastic left heart syndrome.

Hypoplastic Left Heart Syndrome at Seattle Children's

Our heart team has treated many children with hypoplastic left heart syndrome. We have extensive experience with the surgery these patients require. We have a pediatric cardiac anesthesia team and a cardiac intensive care service ready to care for children who undergo heart surgery. We also have a heart transplant program for children who need a transplant. Our team performs several transplants each year for children with this or other heart problems that cannot be controlled using other treatments.

When you come to Children's, a team of people will take care of your child. Along with your cardiologist, you are connected with neonatologists, pediatric cardiac intensive care doctors, nurses, child life specialists, social workers and others, if their expertise is needed. We work together to meet all of your child's health needs and help your family through this experience.

Since 1907, Children's has been treating children only. Our team members are trained in their fields and also in meeting the unique needs of children. For example, the doctors who give your child anesthesia are board certified in pediatric anesthesiology. This means they have extra years of training in how to take care of kids. Our child life specialists know how to help children understand their illnesses and treatments in ways that make sense for their age. Our expertise in pediatrics truly makes a difference for our patients and families.

The Adult Congenital Heart Disease Program shared by Children's and the University of Washington can help with care throughout your child's life.


Saving Baby Poppy

Before she was born, Poppy Dahl was diagnosed with hypoplastic left heart syndrome. Watch her story of survival and learn how her care team worked to give her a fighting chance.