Hypoplastic Left Heart Syndrome

What is hypoplastic left heart syndrome?

Hypoplastic left heart syndrome is a defect in which several things have gone wrong before birth during the development of the left side of the heart:

• The mitral valve, which normally separates the upper and lower left heart chambers, is either poorly developed (mitral stenosis) or not formed at all (mitral atresia).
• The lower left heart chamber (left ventricle) is poorly developed.
• The valve from the left ventricle to the aorta, the artery that normally carries blood from the left ventricle to the rest of your body, is either extremely small (aortic stenosis) or fails to develop (aortic atresia).

The result is that the left side of the heart (left atrium, left ventricle, and aortic valve) does not work and is unable to pump blood to the body.

How does it occur?

Nobody knows why the developmental problems that result in hypoplastic left heart syndrome occur.

What are the symptoms?

Babies with hypoplastic left heart syndrome may be in distress shortly after birth. They are usually gray or blue (cyanotic), feed poorly, and do not grow. Without treatment, they will not survive.

How is it diagnosed?

An ultrasound will show that the structures normally on the left side of the heart are poorly formed. Rarely, cardiac catheterization is needed to confirm the diagnosis. Cardiac catheterization is a procedure in which a thin tube is threaded through a blood vessel to assess the condition of the heart.

How is it treated?

There are three treatment choices for infants with hypoplastic left heart syndrome:

• Do nothing. These babies generally do not suffer and die peacefully in their sleep within the first week or so after birth.
• Do a Norwood procedure. This requires three open-heart surgeries during the first 2 or 3 years of life. The surgeries are designed to have the oxygen-poor (blue) blood flow directly to the lungs and use the right pumping chamber (right ventricle) to pump blood out of the aorta.
• Do a heart transplant.

Parents of infants with hypoplastic left heart syndrome should discuss all three options with their doctor.

What to expect after surgery?

Infants who have a Norwood procedure are often very sick during the various stages of the procedure. This procedure has not been done long enough to know how these children do as teenagers and adults.

The Norwood procedure is used more often, because of the shortage of donor hearts for transplants. Improvements continue to be made in how heart transplants are done in infants. Some of these babies go on to lead normal, productive lives.