Hypoplastic left heart syndrome refers to underdevelopment of the left side of the heart. This syndrome may include:

• A very small (hypoplastic) left ventricle (the lower chamber which normally pumps blood out to the body): It is too small to pump enough blood throughout the body.

• Small aorta: This is the major blood vessel from the left ventricle to the body.

• Aortic valve atresia (absence): This valve normally opens and closes to let blood flow from the left ventricle to the aorta. When atresia is present, there is no connection between the left ventricle and aorta, and no forward blood flow.

• Mitral valve stenosis or atresia: This valve normally opens and closes to let blood flow between the left atrium and left ventricle. Stenosis causes little blood flow; atresia causes no blood flow. Either atresia or stenosis may be present.

Your physician can explain which defects are present in your child.

This very serious combination of heart defects results in little red blood (blood high in oxygen) getting to the body. Two normal connections that infants are born with, provide some blood flow. These connections allow the infant to appear healthy at birth. However, as these connections begin to close, the infant quickly becomes critically ill. Surgery for this defect may be performed in stages or cardiac transplantation may be considered. Successful surgery has only been accomplished in the last few years and long term results remain unknown.