Hypoplastic Left Heart Syndrome

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.

Diagnosis

An echocardiogram will confirm a diagnosis of hypoplastic left heart syndrome.

Treatment

Treatment for hypoplastic left heart syndrome requires open-heart surgery, either in the form of a transplant or a three-step series of operations called staged palliation. Transplant currently results in a lifetime of dependency on antirejection medications as well as a weakened immune system. Suitable donor hearts for babies also are always in short supply.

Staged palliation is considered one of the major achievements of congenital heart surgery in recent years. The survival rate for children at age 5 is about 70 percent and most of these children have normal growth and development. They will require life-long follow-up cardiac care as well as medication. They also will be more prone to heart valve infections, called endocarditis, and require antibiotics before surgery or dental treatment.

The procedures are timed to coincide with the development of the lungs. At the end of the procedures, the lungs allow deoxygenated blood to flow directly to the lungs and back into the heart without having to be pumped. The single ventricle created during the first procedure pumps oxygenated blood from the heart to the body.

• Norwood Procedure -- This procedure is performed shortly after birth. It converts the right ventricle into the main ventricle pumping blood to both the lungs and the body. The main pulmonary artery and the aorta are connected and the main pulmonary artery is cut off from the two branching pulmonary arteries that direct blood to each side of the lungs. Instead, a connection called a shunt is placed between the pulmonary arteries and the aorta to supply blood to the lungs.

• Bi-directional Glenn Operation -- This operation usually is performed about six months after the Norwood to divert half of the blood to the lungs when circulation through the lungs no longer needs as much pressure from the ventricle. The shunt to the pulmonary arteries is disconnected and the right pulmonary artery is connected directly to the superior vena cava, the vein that brings deoxygenated blood from the upper part of the body to the heart. This sends half of the deoxygenated blood directly to the lungs without going through the ventricle.

• Fontan Operation -- This is the third stage, usually performed about 18-36 months after the Glenn. It connects the inferior vena cava, the blood vessel that drains deoxygenated blood from the lower part of the body into the heart, to the pulmonary artery by creating a channel through or just outside the heart to direct blood to the pulmonary artery. At this stage, all deoxygenated blood flows passively through the lungs.