Heart defects are the most common of all birth defects. Roughly 8 in 1000 babies born - that is around 40,000 babies each year in the USA - are born with structural problems in their heart. The term doctors use for these problems is Congenital (meaning you are born with it) Heart Disease - or CHD.
CHD comes in all forms. Every heart created is like a flower.
Most often, these defects are structural - meaning the heart forms differently and is shaped differently than normal. These differences affect how the heart works.
There are many types of CHD, some mild and some severe. Mild types, such as small holes between the inside walls of the heart, may cause a murmur (a sound when the doctor listens to the chest with a stethescope) but may be easily corrected or may close on their own.
The most severe types of CHD are life-threatening - babies will die if they do not receive surgery. Often, even with surgery, the baby is left with a heart that is very different from normal. This may affect the life of the child - how the child grows, thinks and learns. Sometimes, even with surgery, the baby does not survive.
CAUSES OF CONGENITAL HEART DISEASE
There are many reasons why the heart of a baby may develop abnormally while in the womb. Here are some examples:
1. Illness during pregnancy - Sometimes, heard defects occur because the mother gets sick. Rubella, also called German measles, is an example of a virus known to cause a specific type of CHD (pulmonary stenosis or narrowing of the pulmonary valve) in the fetus if a mother catches it during pregnancy. Luckily, most people receive the vaccine against rubella for this very reason - to protect the hearts of unborn babies! Other conditions, such as diabetes (high blood sugar) in the mother, can also cause heart defects in the fetus.
2. Vitamin deficiency during pregnancy - If there are not enough of the building blocks necessary for the heart to develop, problems can develop. One example of an important building block is folate, also known as folic acid. This vitamin is important not just for the heart but also for the spinal cord. Babies born to mothers with folic acid deficiency can have CHD (most often problems affecting the highways that leaves the heart to travel to the lungs) as well as a condition called spina bifida. All women of child-bearing age should make sure they are getting enough enough folate in their diet. A multivitamin will usually do the trick. Because the heart develops so early in pregnancy (formation is near complete by around 10 weeks!) problems can happen before a mother even knows she is pregnant.
3. The mother comes in contact with something bad during pregnancy - Smoking is known to cause CHD. Other types of pollution or chemicals that can be breathed or eaten can also cause heart problems in babies. Some medications, such as pills to control seizures, are also known to cause heart defects.
3. Genetics - Some heart problems happen because the instructions on how to build the heart are faulty. These instructions are found in the genes passed down from parents to child. If a mother or a father - or a sibling, uncle, grandparent etc. - has a heart problem, the chance of a baby having a heart problem is increased. Sometimes doctors can perform a test to find the exact problem in the genes and test for that problem in family members (including unborn babies). Sometimes doctors do not know what the exact problem is and/or no test is available. An example of a genetic problem that can cause heart defects is Trisomy 21 - or Downs Syndrome (when a person has an extra copy of chromosome 21). Half of all babies born with Downs Syndrome have heart problems. It is also important to know that some genetic problems happen during the process of creating a baby - meaning the problems are not present in the parents or other family members. Think of a recipe to make cookies that gets ripped as it is passed from one person to another and the key ingredient of flour is no longer readable. These types of genetic problems are called 'de novo' meaning NEW.
4. Multifactorial - this is a fancy doctor word meaning 'many factors'. Most often doctors do not know why CHD happens. No one in the family has a heart problem. The mother is healthy and did everything right during pregnancy, yet still a baby is born with an abnormal heart. Scientists and doctors are working hard to find out what these unknown causes could be and what can be done to prevent heart problems in babies.
NORMAL HEART
What does the heart do? It is in charge of pumping blood. The heart has to pump blood both to the body and to the lungs.
Why does the heart need to send blood to the body? To deliver oxygen to all the organs and muscles (and pick up carbon dioxide - which is left over after the cells use the oxygen). Without oxygen, the cells of the body will die.
Why does the heart need to send blood to the lungs? To pick up oxygen (and get rid of carbon dioxide).
Did you know the heart has two sides to do this? The RIGHT SIDE of the heart pumps blood to the lungs. The LEFT SIDE of the heart pumps blood to the body.
Both sides of the heart have two rooms (doctors call them chambers because we like to be fancy). The first chamber is called the ATRIUM. The atrium is like the entryway of a building. It's where the blood enters the heart. The second chamber is called the VENTRICLE. The ventricles is the powerhouse. It is the strong muscle that pumps the blood out of the heart to where it needs to go. Because there is a right and a left side of the heart, there is a right atrium and a left atrium, as well as a right ventricle and a left ventricle.
How does the blood get to the heart? VEINS are the vessels that bring blood back to the heart. Most people think that veins only carry blue blood - or blood without oxygen. But that is actually not true! (read below to find out why). Remember, blood that has already fed the body has to travel back to the heart so it can be pumped to the lungs to pick up more oxygen.
On the right side of the heart, there are two big veins: the inferior vena cava (IVC) and the superior vena cava (SVC). The IVC brings blood from the lower body to the right side of the heart. The SVC brings blood from the upper body (head and arms) to the right side of the heart.
On the left side of the heart, PULMONARY VEINS bring blood back from the lungs. Most often there are four of them. This blood, now filled with oxygen, goes to the left atrium. Since this blood has oxygen, it looks brighter red. The PULMONARY VEINS are the only veins in the body that carry oxygenated or red blood.
The highways or blood vessels that leave the heart are called ARTERIES. Most people think arteries only carry bright red blood that has oxygen. But that is not true either!
On the right side of the heart, there is one big highway that travels to the lungs. This highway is called the PULMONARY ARTERY. It brings blood to the lungs. The PULMONARY ARTERY is the only artery in the body that carries blue blood or blood without oxygen.
On the left side of the heart, there is one big highway that travels to the body. This highway is called the AORTA. It brings blood to the body. This blood carries oxygen and is bright red.
HEART OF A FETUS
Can you guess why the heart of a fetus (that's the name for a baby before it is born) is different from that of a baby (and an adult)?
Here's a hint: does the fetus get oxygen from its own lungs? Is the fetus breathing?
NO! The fetus gets oxygen from the mother, from the mother's placenta to be exact. Therefore, the heart of a fetus does not need to pump blood to its lungs. In fact, less than 10% of the blood of a fetus passes through the lungs since the lungs are collapsed and filled with fluid.
Because of this, the fetal heart is different from the heart of a baby or an adult. These differences are what allow most fetuses to survive severe heart defects while inside the mother.
1) There is an extra blood vessel in the fetus that allows the blood to BYPASS the lungs. This is called the DUCTUS ARTERIOSIS. This blood vessel connects the pulmonary artery (the highway leading to the lungs) and the aorta (the highway leading to the body). It is like a shortcut. After a baby is born, the ductus arteriosus is supposed to close. If it remains open, it is called a PATENT (meaning still open) DUCTUS ARTERIOSIS - or PDA (no - not that type of PDA!). Many babies who are born prematurely, meaning earlier than expected, will have a PDA. The PDA can cause problems in babies after they are born because too much blood will end up going to the lungs and the lungs can get flooded. In certain types of severe CHD, the PDA is very important to keep the baby alive while awaiting surgery.
2) The wall between the two upper chambers of the heart - the right and left atrium - has a hole in it. This is called the FORAMEN (fancy word for hole) OVALE (fancy word for oval shape). This hole allows blood coming into the heart from the placenta to go directly to the left side of the heart to bring oxygen to the heart muscle and brain. The heart and brain are greedy like that - they want to get at all the yummy oxygen before the rest of the body. And they should - because they are very important. After a baby is born, this hole is closed by a flap. If it remains open, it is called a PATENT (fancy word for open) FORAMEN OVALE or PFO.