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The heart performs the critical job of pumping blood to and from the lungs and throughout the body. Because its work never stops, this pump must be strong enough to meet all the body’s needs. Patients with hypoplastic left heart syndrome (HLHS) have several important structures on the heart’s left side that fail to develop properly. This malfunction occurs during fetal development and can compromise the baby’s health and even his or her survival. HLHS occurs more often in boys than girls.
In order to fully understand this congenital heart defect, it is helpful to know how a healthy heart works. The human heart has four chambers—the right atria and ventricle, and the left atria and ventricle. The atria are the upper chambers, and the ventricles are the lower chambers. In a healthy heart, the right and left sides of the heart work together. The right side sends blood to the lungs, where it picks up oxygen. The blood returns to the left side of the heart, where it is pumped into the aorta and circulates through the entire body.
In babies with HLHS, the left atria and ventricle, as well as the aorta and the valves that control the flow of blood (the aortic and mitral valves) are so poorly formed that the left side of the heart cannot do its job of pumping blood to the body. This means the right side of the heart must also perform the work of the left side to ensure blood reaches the rest of the body. While the heart may function this way for a short time, it cannot sustain this workload forever.
During fetal development, two small openings form between the right and left sides of the heart. These openings are the ductus arteriosus (a small vessel that connects the pulmonary artery to the aorta) and the foramen ovale (a hole between the right and left atrium). During the first hours and days of life, the right side can pump oxygen-rich blood through these openings in a child born with HLHS. However, when these holes close naturally in the days after birth, it becomes difficult for oxygenated blood to reach the body, and the baby will begin to show symptoms.
Some children are also born with an atrial septal defect (ASD)—a hole between the right and left atria that lets the right side continue pumping blood to the body, even if the ductus arteriosis and foramen ovale are closed.
When a baby does not have ASD, the effects of HLHS are more serious. In these cases, deliveries must be carefully planned because infants require immediate attention by expert surgeons at birth. Maternal Fetal Medicine specialists and pediatric heart surgeons at Riley at IU Health work as a team to coordinate care for mothers and babies in an advanced facility that places operating rooms side-by-side with delivery rooms.
Researchers have not yet discovered the cause of HLHS. Families that have one child with HLHS also have a higher risk of having another child with the same condition. Given the genetic link to this condition, some families choose to better understand their risk through genetic counseling. Expert doctors and genetic counselors in our Cardiovascular Genetics Program can work with your whole family to evaluate and screen for inherited cardiovascular disease.
Babies with HLHS are symptomatic at birth or shortly thereafter. Doctors and parents may notice:
The infant’s color will be gray or blue.
HLHS can be diagnosed during the second trimester of pregnancy with a routine prenatal ultrasound or a fetal echocardiogram. The latter test is especially helpful because it provides details about how the heart functions and other associated heart abnormalities, such as vein anomalies or a heart located on the wrong side of chest.
After the baby is born, a heart murmur or blue/gray skin may cause your physician to suggest further testing. A definitive diagnosis can be made with an echocardiogram.
All babies born with HLHS require surgery. Until the baby is stable enough for surgery, the condition can be managed in numerous ways. Medications can make it easier for blood to flow, force the ductus arteriosus to remain open and make the heart muscle stronger. A ventilator can give the baby adequate oxygen. Intravenous fluids and good nutrition help babies gain weight and get ready for surgery.
Another procedure, an atrial septostomy, may be necessary if the baby’s foramen ovale has closed or it is not present at birth. This procedure creates an opening between the atria. If the baby is also born with an atrial septal defect, it may be unnecessary.
Infants with HLHS typically require three reconstructive surgeries (Norwood surgery, bi-directional Glenn procedure and Fontan procedure) to improve the functioning of the heart, ensure there is sufficient blood flow to the entire body and alleviate cyanosis—the condition that causes a baby to turn blue. These surgeries take place periodically between birth and age 3.
A heart transplant may also be an option. Riley at IU Health is one of only 30 plus hospitals in the nation that is certified to perform heart transplant. Our cardiothoracic surgeons are expertly prepared to assist families as they progress through this treatment and the uncertainties of this rare and life-threatening condition.
Although these surgeries are helpful, they are not a complete cure, and most children continue to experience some problems afterwards. They may have heart rhythm disturbances or be overly tired after physical activity. Therefore, exercise should be done cautiously after evaluation by a cardiologist who specializes in congenital heart defects. Other serious problems that may occur post-surgery include:
When they become adults, patients with HLHS should seek follow-up care from a cardiologist who specializes in caring for adults with congenital heart disease.
These resources can be helpful for parents and caregivers whose children are diagnosed with congenital heart defects.
Riley at IU Health offers a broad range of supportive services to make life better for families who choose us for their children's care.
This U.S. government website includes resources to educate parents and caregivers of children with congenital heart disease. It also shares information for the growing population of adults who are living with congenital heart disease.
As part of the National Institutes of Health, the National Heart, Lung and Blood Institute advances research and understanding of heart, lung and blood diseases and shares easy-to-digest information about congenital heart defects.
Through a grant from the National Institutes of Health, researchers at the Indiana University School of Medicine are studying ways to improve the Fontan procedure—the final step in a three-part strategy currently used to treat HLHS. This research aims to design a dedicated pump that could restore normal circulatory physiology and prevent Fontan failure, which is now a common result of treatment for single ventricle heart disease.
In addition to our primary hospital location at the Academic Health Center in Indianapolis, IN, we have convenient locations to better serve our communities throughout the state.
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