Hypoplastic left heart syndrome

HLHS typically occurs sporadically (randomly), in otherwise normal babies with no family history of HLHS. In a few children, isolated HLHS is known to be genetic. These cases may be due to mutations in the GJA1 gene with autosomal recessive inheritance, or the NKX2-5 gene with autosomal dominant inheritance.

Most congenital heart defects are thought to be caused by interactions between unidentified genes and the environment. This is called multifactorial inheritance. When the specific cause of isolated HLHS in a child is not known, the recurrence risk of left heart disease in first degree relatives of infants with HLHS is estimated at 2 to 4 percent.

HLHS has also been reported with certain genetic disorders including Turner syndrome, Jacobsen syndrome, trisomy 13, and trisomy 18.

The best time to learn about genetic risks and testing options is before pregnancy. Assessing risks in families affected by congenital heart disease (CHD) is a complex process that takes into account the affected family member's heart defect, medical history, physical and other characteristics, as well as the family medical history. In general, people who may benefit from preconception genetic counseling for CHD include:

Adults who have CHD, to learn more about risks to their children
Parents of a child with CHD, to learn more about risk to siblings
People with a strong family history of CHD
People with signs and symptoms of a genetic syndrome associated with CHD, such as distinct facial characteristics, birth defects, learning impairment, behavioral and/or psychiatric disorders
People with types of CHD known to occur in association with a genetic condition, such as 22q11.2 deletion

When genetic testing is available, testing typically begins with the family member who has CHD when possible. Testing on this individual has the greatest likelihood of finding a genetic cause for CHD. Currently clinical genetic testing is available for only select causes of CHD. Most cases of isolated CHD are thought to be sporadic and informative genetic tests are not readily available. If you are unsure if your son would benefit from genetic counseling, we encourage him to speak with his healthcare provider.

In addition, you may find the following article to be a helpful resource. The article provides a comprehensive overview of healthcare decisions and testing considerations couples can make to help ensure a healthy pregnancy.

Brundage SC. Preconception Health Care. American Family Physician. 2002 Jun 15;65(12):2507-2515.

Hypoplastic left heart syndrome (HLHS) is a heart condition present from birth (congenital heart defect). In HLHS, the heart's left side (including the aorta, aortic valve, left ventricle and mitral valve) is underdeveloped. At birth, oxygen-rich blood bypasses the underdeveloped left side of the heart, going through openings between the left and right side that normally close a few days after birth (the patent ductus arteriosus and the patent foramen ovale). The right side of the heart then pumps blood to the lungs and the body. Therefore, there may be no symptoms for a few days. However, when these openings close, oxygen-rich blood cannot easily get to the rest of the body. Symptoms then develop quickly, and may include problems breathing, pounding heart, weak pulse, and/or an ashen or bluish skin color. Some children with HLHS also have other heart defects, such as an atrial septal defect.

In most children with HLHS, the cause is not known. It typically occurs sporadically in otherwise normal babies. In some children, isolated HLHS is known to be genetic. These cases may be due to mutations in the GJA1 gene with autosomal recessive inheritance, or the NKX2-5 gene with autosomal dominant inheritance. HLHS has also been reported with certain genetic disorders including Turner syndrome, Jacobsen syndrome, trisomy 13, and trisomy 18.

If not treated, HLHS is fatal within the first few days or weeks of life. While treatment is difficult, surgical and medical interventions have improved chances of survival. Treatment may include a series of surgeries to restore function to the left side of the heart (staged reconstruction), or heart transplant. However, even with treatment, lifelong complications are possible and life expectancy may be reduced.

If left untreated, HLHS is fatal. Survival rates for the staged surgical repair continue to rise as surgery techniques and care after surgery improve. There are currently estimates of three- to five-year survival rates of 70% for infants who have the stage I repair. For children who survive to the age of 12 months, long-term survival is about 90 percent. The size and function of the right ventricle are important in determining the child's outcome after surgery.

There is little data on the quality of life for patients with HLHS. With more people surviving the staged surgeries, more information is now being gathered about the long-term experiences of people born with HLHS. There is significant morbidity for those who survive treatment for HLHS, including an increased risk of thrombotic (blood clotting) complications, decrease in exercise tolerance, and neurodevelopmental impairment. Thrombotic complications may be associated with mortality, stroke, and pulmonary embolism.

The Centers for Disease Control and Prevention (CDC) has estimated that each year about 960 babies in the United States are born with hypoplastic left heart syndrome (about 1 in every 4,344 babies). HLHS accounts for 2 to 3 percent of all congenital heart disease. The number of cases may be underestimated due to the unknown rate of miscarriages or elective pregnancy terminations of unborn babies with HLHS.

Once the diagnosis of HLHS is made, the baby will likely be admitted to the neonatal intensive care unit (NICU). Management options should be clearly explained to parents and families to allow them to make the best possible informed decision. Choices for management may include staged surgeries, heart transplantation, and comfort care measures (with no surgical interventions). Most pediatric cardiologists and surgeons in the US recommend staged surgery, and there is debate among experts about whether comfort care should be offered as an option at all. Improvements in medical and surgical care have improved outcomes for children with HLHS significantly. However, babies that are treated with surgery are not guaranteed to survive. While some doctors consider heart transplantation an alternative to the 3 step surgery, there are few donated hearts available for small infants.

Initial management focuses on helping the baby breathe and keeping the ductus arteriosis open so blood circulates through the body (with prostaglandin E1). These measures stabilize the baby until the first surgery is performed.

Staged surgery consists of 3 procedures: one in the neonate, one at 3 to 6 months of age, and one at 18 to 30 months of age. The choice of the specific procedure for each stage may vary depending on the baby's individual circumstances. Some people may need more surgeries later on if they develop complications from the condition or from prior surgeries.