Hypoplastic left heart syndrome is a birth defect in which the left side of the heart, including the lower heart chamber (left ventricle), heart valves (mitral and aortic valves), and aorta, does not develop sufficiently. Newborns with hypoplastic left heart syndrome also have an atrial septal defect (ASD) and a patent ductus arteriosus.
Hypoplastic left heart syndrome causes heart failure shortly after birth—the heart pumps less than normal amount of blood to the body—and eventually death.
Diagnosis is by echocardiography.
Treatment is with emergency medications to keep the ductus arteriosus open followed by a series of surgical procedures or with heart transplantation.
(See also Overview of Heart Defects.)
Hypoplastic left heart syndrome accounts for 2 to 4% of heart defects. Hypoplastic is a medical term for a body part that is underdeveloped and small.
In newborns with this heart defect, because the left side of the heart is underdeveloped, when blood flows from the lungs into the left side of the heart, there is very little space in their left atrium. This causes some of the blood to be pushed into the right side of the heart through an atrial septal defect (a hole in the heart wall between the left and right atria). Also, blood returning to from the body (blood with a low oxygen level) mixes with blood returning from the lungs (blood with a high oxygen level).
The underdeveloped left side of the heart does not allow enough blood to return to the body, so the newborn depends on additional blood flow through the ductus arteriosus (a short-cut that is part of the fetal circulation allowing blood to flow directly from the pulmonary artery to the body), but this short-cut usually closes soon after birth (see Normal Fetal Circulation). If the ductus is not kept open by quickly starting a medication called a prostaglandin, the newborn will die. Surgical treatment is required within the first weeks of life.
Symptoms of Hypoplastic Left Heart Syndrome
Symptoms of hypoplastic left heart syndrome appear when the ductus arteriosus begins to close during the first 24 to 48 hours of life. Subsequently, signs of heart failure and shock, including rapid breathing, shortness of breath, weak pulse, pale or bluish skin, cool body temperature, lethargy, and a decreased number of wet diapers, rapidly develop. When blood flow to the body is reduced, the heart, brain and other vital organs do not receive sufficient blood flow. Unless blood flow is re-established, the infant will die.
Diagnosis of Hypoplastic Left Heart Syndrome
Echocardiography
Many infants are diagnosed before birth when hypoplastic left heart syndrome is detected on a prenatal ultrasound examination done on the mother or on echocardiography (ultrasonography of the heart) done on the fetus.
Diagnosis is suspected when doctors notice the symptoms and findings of heart failure while examining the infant. Diagnosis is confirmed by emergency echocardiography.
Chest x-rays and electrocardiography (ECG) may be done. Cardiac catheterization is occasionally needed.
Treatment of Hypoplastic Left Heart Syndrome
A medication (a prostaglandin) to keep the ductus arteriosus open until surgery
Surgical repair
Sometimes heart transplantation
Because most affected children with hypoplastic left heart syndrome are identified before birth, doctors begin giving a medication to keep the ductus arteriosus open immediately after birth, even before any symptoms develop.
Immediate care
Affected infants are treated in a neonatal intensive care unit or pediatric cardiac intensive care unit. A prostaglandin is given by vein to prevent closure of the ductus arteriosus or to reopen a closed ductus. Newborns, particularly those that are critically ill, usually require assistance with breathing (mechanical ventilation). Severely ill newborns may require medications to improve their heart function.
Surgical repair
Survival ultimately requires a series of surgical procedures that enable the right ventricle to take over the work of the underdeveloped left ventricle.
Surgery is done in several stages over the course of 2 to 3 years.
Stage 1: Done during the first weeks of life. This involves a complex repair called a Norwood procedure, which allows the right side of the heart to supply blood to the body.
Stage 2: Done when the infant is 3 to 6 months of age. This operation is known as a Glenn procedure. It directs the blood coming back to the heart from the upper half of the body directly into the pulmonary artery, bypassing the heart.
Stage 3: Done when the child is 18 to 36 months of age. If infants have had good results from the first 2 stages of repair, then they undergo the third stage, which is called a Fontan procedure. This operation directs the blood returning from the lower half of the body to the pulmonary artery, resulting in all of the venous blood bypassing the heart on its way to the lungs.
Heart transplantation
In some medical centers, heart transplantation is considered the procedure of choice for hypoplastic left heart syndrome. Infants must be given an infusion of a prostaglandin to keep the ductus arteriosus open until a donor heart is available. Because availability of donor hearts is very limited, about 20% of infants die while awaiting transplant. The 5-year survival rates after transplantation and after multistage surgery are similar. However, because of the limited donor issue and improved surgical outcomes, most congenital heart disease treatment centers recommend the multistage surgical approach.
After heart transplantation, medications to suppress the activity of the immune system (immunosuppressants) are required for the rest of the child's life. These medications make people more susceptible to infections and increase the risk of developing certain tumors. Immunosuppressants may also damage the coronary arteries of the transplanted heart. The only known treatment for coronary artery damage is retransplantation.
Long-term care
Some children, depending on the result of their surgical procedures, need to take antibiotics before visits to the dentist and before certain surgeries (such as on the respiratory tract). These antibiotics are used to prevent a serious heart infection called endocarditis.
Most children need to take aspirin
More Information
The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
American Heart Association: Common Heart Defects: Provides an overview of common birth defects of the heart for parents and caregivers
American Heart Association: Infective Endocarditis: Provides an overview of infective endocarditis, including summarizing antibiotic use, for parents and caregivers
