Hypoplastic left heart syndrome

DEFINITION

Hypoplastic left heart syndrome is a complex and rare heart defect present at birth (congenital). In hypoplastic left heart syndrome, the left side of the heart is critically underdeveloped.

If your baby is born with hypoplastic left heart syndrome, the left side of the heart can’t effectively pump blood to the body, so the right side of the heart must pump blood both to the lungs and to the rest of the body.

Medication to prevent closure of the connection (ductus arteriosus) between the right and left sides, followed by either surgery or a heart transplant, is necessary to treat hypoplastic left heart syndrome. With advances in care, the outlook for babies born with hypoplastic left heart syndrome is better now than in the past.

CAUSES

Hypoplastic left heart syndrome occurs during fetal growth when the baby’s heart is developing. The cause is unknown. However, if your family has one child with hypoplastic left heart syndrome, the risk of having another with the same condition is increased.

A normal heart has four chambers, two on the right and two on the left. In performing its basic job — pumping blood throughout the body — the heart uses its left and right sides for different tasks. The right side moves blood to the lungs. In the lungs, oxygen enriches the blood, which then circulates to the heart’s left side. The left side of the heart pumps blood into a large vessel called the aorta, which circulates the oxygen-rich blood to the rest of the body.

What happens in hypoplastic left heart syndrome

In hypoplastic left heart syndrome, the left side of the heart can’t properly supply blood to the body because the lower left chamber (left ventricle) is too small or in some cases it may not even exist. In addition, the valves on the left side of the heart (aortic valve and mitral valve) don’t work properly, and the main artery leaving the heart (aorta) is smaller than normal.

For the first several days of life, the right side of the heart can pump blood both to the lungs and to the rest of the body through a natural opening (foramen ovale) between the upper chambers of the heart (atria) or through a blood vessel that connects the pulmonary artery directly to the aorta (ductus arteriosus). When the foramen ovale and the ductus arteriosus are open, they are referred to as being “patent.”

If the ductus arteriosus and the foramen ovale close — which they normally do after the first day or two of life — the right side of the heart has no way to pump blood out to the body. However, many infants with hypoplastic left heart syndrome also have another heart defect, a hole in the wall between the upper chambers of the heart (atrial septal defect), that allows the right side of the heart to continue pumping blood to the body even if the ductus arteriosus or foramen ovale closes.

SYMPTOMS

Babies born with hypoplastic left heart syndrome usually are seriously ill immediately after birth. Hypoplastic left heart syndrome symptoms include:

• Grayish-blue skin color (cyanosis)
• Rapid, difficult breathing
• Poor feeding
• Cold hands and feet
• Being unusually drowsy or inactive

In a baby with hypoplastic left heart syndrome, if the natural connections between the heart’s left and right sides (foramen ovale and ductus arteriosus) are allowed to close, he or she may go into shock and may die. Signs of shock include:

• Cool, clammy skin that may be pale or gray
• A weak and rapid pulse
• Abnormal breathing that may be either slow and shallow or very rapid
• Dilated pupils
• Lackluster eyes that seem to stare

A baby who is in shock may be conscious or unconscious. If you suspect your baby is in shock, immediately call 112 or your local emergency number.

When to see a doctor

It’s more likely that your baby would be diagnosed with hypoplastic left heart syndrome either before birth or soon after. However, you should seek medical help if you notice that your baby has the following symptoms:

• Grayish-blue skin color
• Rapid, difficult breathing
• Poor feeding
• Cold hands and feet
• Being unusually drowsy or inactive

If your baby has any of the following signs of shock, call 112 or your local emergency number right away:

• Cool, clammy skin that may be pale or gray
• A weak and rapid pulse
• Abnormal breathing that may be either slow and shallow or very rapid
• Dilated pupils in the eyes
• Lackluster eyes that seem to stare