Hypoplastic Left Heart Syndrome (HLHS)

Overview

In hypoplastic left heart syndrome, the left side of the heart — the part that pumps oxygenated blood to the rest of the body — is underdeveloped. Its two chambers, called the left atrium and the left ventricle, and their valves may be tiny, blocking the flow of oxygenated blood from the lungs.

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.

Babies with hypoplastic left heart syndrome may seem healthy at birth because the patent ductus arteriosus (PDA) is still open. The PDA is a blood vessel that connects the pulmonary artery to the aorta, allowing blood to continue circulating directly into the aorta and out to the rest of the body, bypassing the lungs and the defective left side of the heart. Once the PDA 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.

Without treatment, babies afflicted with hypoplastic left heart syndrome can die within the first days or weeks of life. Treatment consists of a heart transplant or a series of operations to restore the function of the left side of the heart. Intravenous medication can keep the PDA open until surgery can be performed, but is not a permanent treatment.

Signs & symptoms

Babies born with hypoplastic left heart syndrome may seem normal at birth but become severely ill soon after birth. Babies may appear ashen or gray, have rapid and difficult breathing and have difficulty feeding. This heart defect is usually fatal within the first days or month of life unless treated.

Symptoms include:

• Grayish-blue skin color
• Rapid, difficult breathing
• Poor feeding
• Cold hands and feet
• Lethargy

Babies with this disorder could go into shock if the blood flow between the right and left sides of the heart is blocked because of the congenital defect. Signs of shock are abnormal breathing, dialated pupils and a weak and rapid pulse.

Diagnosis

A diagnosis of hypoplastic left heart syndrome is confirmed with an echocardiogram, a test that uses sound waves to create a moving picture of the heart.

Treatment

Treatment for hypoplastic left heart syndrome requires either a three-step surgical procedure called staged palliation or a heart transplant.

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. This three-step surgery procedure is designed to create normal blood flow in and out of the heart, allowing the body to receive the oxygenated blood it needs.

The three steps consist of the following procedures:

• 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 to 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.

Heart transplant is another option for infants with hypoplastic left heart syndrome. However, suitable donor hearts for babies are often in short supply.

Hypoplastic left heart syndrome sufferers will require life-long cardiac care as well as medication. They also will be more prone to heart valve infections, called endocarditis, and will need to take antibiotics before surgery or dental treatment.