Congenital Heart Disease

Hypoplastic Left Heart Syndrome

Signs and Symptoms
Diagnosis
Treatment

Signs and Symptoms

Hypoplastic left heart syndrome is when the left side of the heart -- the part that pumps oxygenated blood to the rest of the body -- is underdeveloped.

The heart consists of four chambers: the two upper chambers, called atria, where blood enters the heart; and the two lower chambers, called ventricles, where blood is pumped out of the heart. The flow between the chambers is controlled by a set of valves that act as one-way doors.

Normally blood is pumped from the right side of the heart through the pulmonary valve and the pulmonary artery to the lungs, where the blood is filled with oxygen. From the lungs, the blood travels back down to the left atrium and left ventricle. The newly oxygenated blood then is pumped through another big blood vessel called the aorta to the rest of the body.

In hypoplastic left heart syndrome, the left atrium and left ventricle, and their valves may be tiny, blocking the flow of oxygenated blood from the lungs. Babies with this condition may appear normal at birth but will die within the first days or weeks of life without treatment. Treatment consists of a heart transplant or a series of operations to restore the function of the left side of the heart.

These babies become pale and have difficulty breathing and feeding, but not right after birth. Fetuses are nourished by oxygen-rich blood from their mothers so they don't breathe and don't use their lungs. Babies with hypoplastic left heart syndrome may seem normal at birth because the patent ductus arteriosus is still open, allowing blood to continue circulating directly into the aorta and out to the rest of the body.

The patent ductus arteriosus is a blood vessel that connects the pulmonary artery to the aorta, thereby bypassing the lungs and the defective left side of the heart. Once the ductus closes a few days after birth, blood flows to the lungs and then to the left side of the heart where it is blocked and can't circulate through the rest of the body. Intravenous medication can keep the ductus open until surgery can be performed but is not a permanent treatment.

Reviewed by health care specialists at UCSF Children's Hospital.
Last updated May 8, 2007