Congenital Heart Defects

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Congenital heart defects (CHDs) comprise the largest single group of birth defects. They affect approximately 4 of every 1,000 births in the United States each year. These defects are multifactorial in origin, which implies an interplay between genetic and environmental factors.

There are many maternal factors that increase the risk of having a pregnancy affected by a CHD. Mothers with diabetes that is not under adequate control are more likely to have a baby with a CHD. Also, if the mother does not take prenatal vitamins containing folic acid, the risk of a heart defect is increased.

There are many types of CHDs are part of the Florida Birth Defects Registry's surveillance system. One of the most serious of these defects is Hypoplastic Left Heart Syndrome.

DEFECT IN REVIEW: HYPOPLASTIC LEFT HEART SYNDROME

What causes hypoplastic left heart syndrome and how common is it?

During the first eight weeks of a pregnancy, while a child’s organs are developing, certain types of problems can happen during the development of a baby’s heart. Hypoplastic left heart syndrome (HLHS) is the name of one set of problems that can impact a child’s heart and connecting blood vessels.

The reasons that some babies develop HLHS are not known. This type of birth defect may not be linked to anything that a mother did either before or during her pregnancy. It has been found that many heart defects may be caused by a problem with the genes that the baby receives from his or her mother or father. Mothers or fathers who have had a baby with HLHS may receive advice to get testing and information from a genetic counselor to help them understand if they are at risk of having another baby with a heart defect.

About one out of every 3,700 babies who are born alive in Florida will have HLHS. Baby boys have a 38% more likely than baby girls to be born with this heart defect.

What is hypoplastic left heart syndrome?

To understand the problems associated with HLHS lets first look at what happens with a heart that did not have a problem during its development. When blood flows through our bodies it supplies our organs with the oxygen that we need to survive. That oxygen is put into our blood by our lungs. Blood that has been supplied with oxygen is called ‘oxygen-rich’. When the oxygen in our blood is used up we call the blood ‘oxygen-poor’. That oxygen-poor blood returns to our heart to get a new supply of oxygen from our lungs. As the arrows in the first diagram show, in a healthy heart, blood that has been supplied with oxygen by our lungs is pumped by the heart’s left ventricle through the aorta into the rest of our body. The oxygen-rich blood moves through our body, supplying oxygen as needed along the way. As the supply of oxygen in the blood is used up, the oxygen-poor blood is returned to our heart through the right atrium. The tricuspid valve controls the flow of blood from the right atrium into the right ventricle. The blood is then pumped by the right ventricle through the pulmonary artery into our lungs where it receives a new supply of oxygen. That blood, which is now oxygen-rich, is then returned to our heart by the pulmonary veins. These veins empty into the left atrium, where the mitral valve controls the flow of blood into the left ventricle. The cycle continues with that oxygen rich blood being pumped back out by the left ventricle through the aortic valve and on into the aorta so our heart can deliver oxygen to the rest of the body again.

Normal Heart Compared to a Hypoplastic Left Heart

There are many problems with the hearts of children who have HLHS. The biggest problem is that the part of their heart that needs to pump oxygen-rich blood to the other organs in their body does not work very well. Instead of the left ventricle being the large, strong chamber that is shown in diagram 1, the left ventricle in a child with HLHS is very small and underdeveloped. Not only does the left ventricle not supply the aorta with enough blood to meet the needs of the rest of the body, the aorta itself is also smaller in a hypoplastic heart than an aorta would be in a heart that developed normally.

Due to other problems in the heart the blood that is pumped by the underdeveloped left ventricle does not have the amount of oxygen that is needed by the other organs in the child’s body. One such problem is that an opening can form in the right atrium. That opening, called an atrial septal defect, allows the blood that has used up its oxygen to mix with the blood that is coming back into the heart from the lungs. Another opening can also form between the aorta and the pulmonary artery. That opening, called a patent ductus arteriosus, also allows oxygen poor blood to mix with the oxygen rich blood that is being pumped out into the body. Because of those two mixing problems, the blood that is pumped by the child’s heart is not able to supply child’s body with enough oxygen. That is why a baby who is born with hypoplastic left heart syndrome may not live for very long without having surgery to repair some of the problems in his or her heart.

How can a doctor tell if a baby has hypoplastic left heart syndrome?

Soon after a baby is born a doctor can usually see symptoms of HLHS. Each baby may show slightly different symptoms, but the most common are having:

skin, lips or nailbeds with a blue color (a condition called cyanosis),
pale skin,
sweaty or mottled skin,
heavy and/or rapid breathing,
a fast heart rate, and;
cold hands and feet that don’t have a good pulse.

Because these symptoms may be caused by other medical conditions the baby’s doctor will use special tests to tell whether or not the baby has HLHS. The doctor may hear a sound called a murmur when he or she listens to the baby’s heart. That sound is caused by problems with the blood pumping from the right ventricle to the pulmonary artery. A specialist, called a pediatric cardiologist, will probably do the additional testing to find out if the baby actually has HLHS or some other heart problem.

Is there treatment for hypoplastic left heart syndrome?

The type of treatment for HLHS will depend on the overall health of the child, the seriousness of the heart defect and other factors that must be discussed with the child’s doctor. Most newborns with HLHS will be put into a special nursery section of the hospital called the neonatal intensive care unit (NICU). The baby may be placed on a breathing machine to help with his or her breathing, and may be given medication to help his or her heart and lungs work better. Even with that help a child with HLHS will need surgery. Because every baby with HLHS is different the doctor will discuss the types of surgery that are available and will explain which one is the best choice. After the surgery has been done the doctors and nurses will explain the next steps in caring for the baby and will try to explain what can be expected regarding the baby’s recovery. Unfortunately even with surgery and the best medical care some babies who are born with HLHS will not be able to get better and may die very young.

Whenever a loved one is dealing with a serious medical issue it is important to get help in understanding all the medical terms that doctors and nurses may use and in understanding explanations about treatment. It is perfectly reasonable that you may not understand something that a doctor or nurse has told you about your child’s illness. Don’t worry about asking too many questions. Ask the doctors and nurses about the things that you don’t understand. If you still have questions try speaking with the medical social worker at the hospital to see if he or she can explain things in a different way. It is also important to find groups and people who can give support, answer questions and offer understanding for the difficult times that you are experiencing. The medical social worker or hospital discharge planner may have information about support groups in your area. These groups are usually made up of moms and dads who are either taking care of a child with HLHS or similar health problems, or are the parents of children who died from a similar medical problem. Speaking with parents who have had similar experiences might be very helpful.

Where can I get more information about hypoplastic left heart syndrome?

Ask the medical social workers or discharge planners at the hospital about local telephone numbers for the support groups in you area. Please also ask for printed material that you can share with your family and friends so they can get more information about how to support you during this difficult time. In addition to speaking with local organizations you can also get more information about hypoplastic left heart syndrome, support group information and other links to other resource on the following websites:

There are many resources that provide detailed information about various forms of CHDs, including information about prevention, causes, diagnosis, treatment, and support or bereavement groups. Please click on the following links to get more information on each of the following heart conditions.

IMPORTANT LINKS AND RESOURCES!!