Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is a serious problem that involves several parts of the left side of the heart. It is quite rare and occurs in about one out of every 5,000 babies born. In the United States, about 1,000 babies with HLHS are born each year. Two thirds of the babies affected are boys. Most babies with HLHS are otherwise healthy, but some have other medical problems including other heart problems, neurologic problems, and Turner's syndrome.

The University of Michigan C.S. Mott Children’s Hospital was among the first congenital heart programs to achieve consistent success in the surgical treatment of HLHS. While historically every baby born with HLHS died in infancy, today – thanks in large part to the heart specialists at University of Michigan – outcomes for children with HLHS have dramatically improved. More than 90 percent of HLHS babies treated at the University of Michigan survive to discharge, making the U-M Congenital Heart Center a worldwide leader in the treatment of HLHS. Learn more about the Congenital Heart Center.

What is hypoplastic left heart syndrome?

In children with HLHS, for unknown reasons, the left side of the heart does not develop properly while the baby is in the mother's womb. The parts of the heart that are usually affected are the mitral valve , the left ventricle, the aortic valve and the aorta. In the normal heart, red blood returning from the lungs, flows from the heart's left upper chamber called the left atrium through the mitral valve to the left ventricle where it is pumped through the aortic valve and out to the body. In babies with HLHS, the left side of the heart is underdeveloped and cannot pump enough blood to meet the body's needs.


How is hypoplastic left heart syndrome diagnosed?

HLHS is often diagnosed before a baby is born, usinga type of specialized ultrasound called a fetal echocardiogram.

If there is a family history of congenital heart disease or if concern is raised during a routine ultrasound, the family is referred to a pediatric cardiology center where a detailed study of the heart is performed. Learn more about our Prenatal Heart Program.

Most newborns with HLHS have mild heart-related symptoms until the patent ductus arteriosus closes, usually within 48 hours of birth. Prior to closure of the ductus arteriosus, the baby's lips or fingernails may look slightly blue, especially when the baby cries. Babies with HLHS often breathe fast, have low energy levels, and/or have feeding problems. These changes can be subtle and can be difficult to detect in a newborn baby. When the ductus arteriosus does close, the baby may get very ill very quickly and develop symptoms of shock.

How is hypoplastic left heart syndrome treated?

For babies diagnosed prenatally, in a small number of cases, fetal intervention for HLHS may be beneficial for babies with a restrictive atrial septal defect. These treatments are not a "cure," however, and children with HLHS will need expert medical attention for the rest of their lives.

For babies with HLHS, treatment generally consists of a three-staged surgical approach, or heart transplantation.

For children who are candidates for surgery, treatment usually consists of three heart operations done during the first two years of life. The goal of these operations is to rebuild the heart so that the right side can be used to pump blood out to the body. The first stage usually consists of a Norwood operation, which is done during the first two weeks of life, but in certain cases a combined surgical and catheterization approach called a Hybrid procedure may be done instead. The Hemi-Fontan procedure is done when the child is about four to six months old, and the Fontan procedure is done when the child is about two years old.

In addition to the three operations, one or more heart catheterizations may also be done. A heart catheterization is a heart test that is done by a cardiologist with the help of cardiovascular technicians. Soft, thin plastic catheters (tubes) are placed in the large blood vessels in the leg and threaded carefully to the heart. The catheters are used to take pressure measurements inside the heart and to inject contrast or dye so pictures of the heart can be taken. Overall, this is a very safe test and children can go home the same day.

Heart transplantation is another option for treatment of children with hypoplastic left heart syndrome, and remains an option even after staged surgical treatment. While the risks associated with the operation itself are quite low at most centers, there can be limited availability of donor hearts of a size suitable for an infant.  Our center has a dedicated transplant team that specializes in caring for the complex long term needs of children who undergo heart transplant.

What are the long-term health issues for children with hypoplastic left heart syndrome?

The outlook for children with HLHS has improved dramatically. While HLHS was once uniformly fatal, our experience so far indicates that the majority of children will now reach adulthood. Some children will need other catheter-based or surgical procedures, such as a pacemaker for abnormal heart rhythms. Others may need a heart transplant. Heart function, as well as the function of other organs that may be impacted by abnormalities in the circulation, will be monitored over the long term.  Overall, it is expected that these children will have a good quality of life: have friends, play, and go to school just like other children.

Exercise guidelines: An individual exercise program is best planned with the doctor.  Regular exercise is encouraged and children with HLHS are most often able to participate in recreational sports and participate in gym class.  Contact sports and other types of vigorous activity may be limited.

Neurodevelopmental delays: Research shows that children who undergo cardiac surgery during the first year of life are at higher risk for developmental, learning, and/or behavioral concerns later in life. Continued evaluation for these children is highly recommended to ensure early identification of delays. The C.S. Mott Children’s Hospital Congenital Heart Center Neurodevelopmental Follow-Up Program offers a complete developmental assessment and referral program to ensure early intervention and support for children experiencing neurodevelopmental delays, and provide a solid foundation for later learning and future development. 

Take the next step:

The University of Michigan C.S. Mott Children’s Hospital is a leader in treatment of hypoplastic left heart syndrome. For more information on our programs and services, or to make an appointment, please call 1-800-475-6688.