What is Hypoplastic Left Heart Syndrome?
A baby with Hypoplastic Left Heart Syndrome has an underdeveloped left ventricle, the heart chamber that pumps blood through the aorta to the entire body. In some cases the mitral valve (which connects the atrium and ventricle), the aortic valve (which connects the heart to the major vessels leading from the lungs), and the ascending aorta (which carries blood from the heart to be distributed through the body) may be absent or underdeveloped. These defects prevent the left side of the baby’s heart from functioning properly. Consequently, the right side of the fetus’s heart takes on the function of pumping blood to the body through the ductus arteriosus into the aorta. The ductus arteriosus is a broad vessel in the fetus that connects the pulmonary artery to the aorta. It allows the blood to bypass the lungs during fetal development since the baby does not breathe until after birth. It normally closes shortly after birth. When it closes in a baby with Hypoplastic Left Heart Syndrome, the blood supply to the baby’s body is cut off.