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—the heart pumps less than normal amount of blood to the body—and eventually death.
- Diagnosis is by echocardiography.
- Treatment is with emergency drugs to keep the ductus arteriosus open followed by a series of surgical procedures or with heart transplantation.
(See also Overview of Heart Defects.)
Hypoplastic is a medical term for underdeveloped and small. Hypoplastic left heart syndrome (HLHS) accounts for 2 to 4% of birth defects of the heart. Because the left side of the heart is underdeveloped, oxygenated blood coming into the left side of the heart from the lungs is diverted into the right side of the heart through an atrial septal defect (a hole in the wall that separates the heart's atria into left and right sides), where it mixes with deoxygenated blood returning to the heart from the body. This relatively deoxygenated blood exits the right heart to the lungs and through the ductus arteriosus to the body. The ductus arteriosus is a blood vessel connecting the two great arteries leaving the heart, the pulmonary artery and the aorta (see Normal Fetal Circulation). In the womb and during the first few days of life, the ductus is open. Blood flow to the body is maintained only because the ductus arteriosus remains open. Once the ductus closes, as it normally does after birth, very little blood flows to the body. If the ductus is not kept open by starting a prostaglandin quickly, the infant 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
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 symptoms during an examination of the infant. Diagnosis is confirmed by emergency echocardiography.
Treatment of Hypoplastic Left Heart Syndrome
- A drug (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 drug to keep the ductus open immediately after birth.
All affected infants are treated in a neonatal intensive care unit or pediatric cardiac intensive care unit. Prostaglandin is given by vein to prevent closure of the ductus arteriosus or to reopen a narrowed ductus. Newborns, particularly those that are critically ill, usually require assistance with breathing (mechanical ventilation). Severely ill newborns may require drugs to improve heart function.
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 is several stages:
- 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.
In some infants, 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.
After heart transplantation, drugs to suppress the activity of the immune system (immunosuppressants) are required for the rest of the child's life. These drugs 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.
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 serious heart infections called endocarditis.
Most children will take aspirin or a blood thinner such as warfarin or enoxaparin to help prevent clots from forming in the heart. Many affected children will need to take one or more other drugs to help their hearts continue to function optimally.
The following are some English-language resources that 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
Drugs Mentioned In This Article
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