Hypoplastic left heart syndrome is a complex and rare heart defect present at birth (congenital). In this condition, 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. Instead, the right side of the heart must pump blood 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. Advances in care have improved the outlook for babies born with this condition.
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Babies born with hypoplastic left heart syndrome usually are seriously ill soon after birth. Signs and symptoms include:
- Grayish-blue skin color (cyanosis)
- Rapid, difficult breathing
- Poor feeding
- Cold hands and feet
- Weak pulse
- Being unusually drowsy or inactive
If the natural connections between the heart's left and right sides (foramen ovale and ductus arteriosus) are allowed to close in the first few days of life in babies with hypoplastic left heart syndrome, they can go into shock and possibly die.
Signs of shock include:
- Cool, clammy skin that can be pale or gray
- A weak and rapid pulse
- Abnormal breathing that may be either slow and shallow or very rapid
- Lackluster eyes that seem to stare
A baby in shock might be conscious or unconscious. If you suspect your baby is in shock, immediately call 911 or your local emergency number.
When to see a doctor
It's 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 any of the signs or symptoms of the condition.
If your baby has signs or symptoms of shock, call 911 or your local emergency number right away.
Chambers and valves of the heart
A normal heart has two upper (receiving) and two lower (pumping) chambers. The upper chambers, the right and left atria, receive incoming blood. The lower chambers, the more muscular right and left ventricles, pump blood out of your heart. The heart valves, which keep blood flowing in the correct direction, are gates at the chamber openings (for the tricuspid and mitral valves) and exits (for the pulmonary and aortic valves).
Hypoplastic left heart syndrome occurs when the baby's heart is developing in the womb. The cause is unknown. However, if your family has one child with hypoplastic left heart syndrome, the risk of having another with a similar 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
Hypoplastic left heart syndrome
In this condition, the left side of the heart — including the aorta, aortic valve, left ventricle and mitral valve — is underdeveloped (hypoplastic). As a result, the body doesn't receive enough oxygenated blood.
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 doesn't 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 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 blood vessel that connects the pulmonary artery directly to the aorta (ductus arteriosus). The oxygen-rich blood returns to the right side of the heart through a natural opening (foramen ovale) between the right chambers of the heart (atria). 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. In babies with hypoplastic left heart syndrome, medication is necessary to keep these connections open and keep blood flowing to the body until heart surgery is performed.
HLHS: A Child's Perspective
If you already have a child with hypoplastic left heart syndrome, you have a higher risk of having another baby with this or a similar condition.
Beyond family history, there are no clear risk factors for hypoplastic left heart syndrome.
Without surgery, hypoplastic left heart syndrome is deadly, usually within the first few days or weeks of life.
With treatment, many babies survive, although most will have complications later in life. Some of the complications might include:
- Tiring easily when participating in sports or other exercise
- Heart rhythm problems (arrhythmias)
- Fluid buildup in the lungs, abdomen, legs and feet (edema)
- Growth restriction
- Formation of blood clots that may lead to a pulmonary embolism or stroke
- Developmental problems related to the brain and nervous system
- Need for additional heart surgery or transplantation
There's no way to prevent hypoplastic left heart syndrome. If you have a family history of heart defects, or if you already have a child with a congenital heart defect, consider talking with a genetic counselor and a cardiologist experienced in congenital heart defects before getting pregnant.
Dec. 03, 2020