In hypoplastic left heart syndrome, the left side of the heart -- including the aorta, aortic valve, left ventricle and mitral valve -- is underdeveloped. Blood returning from the lungs must flow through an opening in the wall between the atria (atrial septal defect). The right ventricle pumps the blood into the pulmonary artery and blood reaches the aorta through a patent ductus arteriosus (see diagram).

The baby often seems normal at birth, but will come to medical attention within a few days of birth as the ductus closes. Babies with this syndrome become ashen, have rapid and difficult breathing and have difficulty feeding. This heart defect is usually fatal within the first days or months or life unless it's treated.

Although this defect is not correctable, some babies can be treated with a series of operations, or a heart transplantation. Until an operation is performed, the ductus is kept open by intravenous medication. Because these operations are complex and need to be individualized for each patient, it's necessary to discuss all the medical and surgical options with your child's doctor. Your doctor will help you decide which is best for your baby.

If you and your child's doctor agree that surgery should be performed, it will be done in several stages. The first stage, referred to as the Norwood procedure, allows the right ventricle to pump blood to both the lungs and the body. It must be performed soon after birth. The final stage(s) has many names, including bi-directional Glenn, Fontan operation and lateral tunnel. These operations create a connection between the veins returning blue blood to the heart and the pulmonary artery. The overall goal of the operation is to allow the right ventricle to pump only oxygenated blood to the body and to prevent or reduce mixing of the red and blue blood. Some infants require several intermediate operations to achieve the final goal.

Some doctors will recommend heart transplantation to treat this problem. Although it does provide the infant with a heart that has normal structure, the infant will require life-long medications to prevent rejection. Many other transplant-related problems can develop, and these should be discussed with your doctor.

Children with hypoplastic left heart syndrome require lifelong follow-up by a cardiologist for repeated checks of how their heart is working. Virtually all the children will require heart medicines. They also risk infection on the heart's valves (endocarditis) and will need antibiotics such as amoxicillin before dental work and certain surgeries to help prevent endocarditis. Good dental hygiene also lowers the risk of endocarditis. For more information about dental hygiene and preventing endocarditis, ask your pediatric cardiologist.