Congenital heart defects occur when the heart or blood vessels near the heart develop abnormally before birth and the baby is born with them.

What causes heart defects?
In most cases the cause is not known. A heart defect forms during early pregnancy (between the 6th and 12th week) - very often before a mother realises that she is pregnant. Sometimes the cause can be identified. A mother may have an increased risk of having a baby with a heart defect if during pregnancy she: has a viral infection such as German measles, suffers from diabetes, conditions such as Down's Syndrome, uses certain medications, abuses alcohol and "street" drugs. A family history also plays a role in congenital heart defects. It is, however, important to emphasise that the abnormality is not the fault of the parents.

What is a heart defect?
How the normal heart works:  On the right side of the heart there is a chamber (the right atrium) that receives deoxygenated blood (the oxygen has been removed by the body cells) from the rest of the body. It then passes through a valve to the right pump of the heart (right ventricle).
 
The blood is pumped from there, into the lungs. The blood receives oxygen from the lungs and returns to the chamber on the left side of the heart (left atrium). It then passes through another valve to the aorta, which is the main artery supplying oxygen-rich blood to the head, body and limbs.

Congenital heart defects affect the normal functions of the heart. Most heart defects either obstruct blood flow to or inside the heart, or cause blood to flow through the heart in an abnormal pattern. The defects range in severity from simple problems to severe malformations that can cause heart failure.

What other types of heart disease are found in children?
Acquired heart disease is heart disease in children that develops after birth, for example heart damage caused by infection (e.g. Kawasaki disease and rheumatic fever). Children can also be born with or develop arrhythmias (heart rate problems such as irregular, slow or fast heart beats).

A.  OBSTRUCTIVE DEFECTS

Obstructive defects (also called stenosis) occur when there is a narrowing in heart valves, arteries or veins that partly or completely block the flow of blood.

The three most common forms:

Pulmonary stenosis:
Narrowing of the pulmonary (lung) valve that normally opens to allow blood to flow from the right ventricle to the lungs. This forces the right ventricle to pump harder than normal to overcome the obstruction and in severe cases cyanosis (blueness of the skin due to a lack of oxygen) might occur.

Aortic stenosis:
Narrowing of the aortic valve (between the left ventricle and the aorta) that results in the heart having difficulty pumping blood to the body.

Coarctation of the aorta ("Coarct"):
The aorta is narrowed and thus obstructs blood flow to the lower body and increases blood pressure above the obstruction. Usually there are no symptoms at birth, but these can develop within the first week after birth. Congestive heart failure or high blood pressure can develop. Related but less common forms include bicuspid aortic valve and subaortic stenosis.

B.  SEPTAL DEFECTS

This defect is sometimes called "a hole in the heart”. An opening between the wall separates the right and left sides of the heart (septum) and allows blood flow between the heart's right and left chambers.

The two most common types:

Atrial septal defect:
An opening exists between the heart's two upper chambers (atria), which allows blood from the left atrium (blood that's already been to the lungs) to return through the hole to the right atrium instead of flowing through the left ventricle, out of the aorta and to the rest of the body.

Ventricular septal defect:
An opening exists between the two lower chambers (ventricles) of the heart. Some blood that has returned from the lungs and been pumped into the left ventricle, flows through the hole into the right ventricle instead of being pumped into the aorta and from there to the rest of the body. Depending on the size of the hole, the heart has to pump harder to supply enough blood to the body, becomes overworked and may become enlarged.

C.  CYANOTIC DEFECTS

A heart defect that causes the blood pumped from the heart to the rest of the body to contain less oxygen than normal and causes a condition called cyanosis, a blue discolouration of the skin. The term "blue baby" is often used. Examples of cyanotic defects are:

Tetralogy of Fallot:
This defect has four components. The two major ones are a large hole (or ventricular septal defect), that lets blood pass from the right to the left ventricle without going through the lungs and a narrowing (stenosis) at or just beneath the pulmonary (lung) valve. This narrowing partially blocks the blood flow from the heart's right side to the lungs. The other two components are: the right ventricle that is more muscular than normal and the aorta that lies directly over the ventricular septal defect. During exercise, older children may become short of breath and faint.

Transposition of the great arteries:
The positions of the pulmonary artery and the aorta are reversed. The aorta is connected to the right ventricle and therefore most of the blood returning to the heart from the body is pumped back out without going to the lungs first. The pulmonary artery is connected to the left ventricle and thus most of the blood returning from the lungs goes back to the lungs again. Infants born with this defect survive only if they have one or more connections that let oxygen-rich blood reach the body, for example a vessel connecting the pulmonary artery with the aorta, called patent ductus arteriosus.

D.  OTHER DEFECTS

Patent ductus arteriosus:
Before birth there's an open passageway (the ductus arteriosus) between the pulmonary artery and the aorta. Normally this passageway closes within a few hours of birth.

When this opening does not close, blood is allowed to flow from the aorta to the lungs. The lungs receive an increased amount of blood and this requires that the heart pumps harder. Depending on the size of the ductus arteriosus, symptoms can be experienced in varying degrees, for example, the child may tire quickly, grow slowly and may be more prone to get pneumonia.

What are the long-term implications for children with heart defects?
Virtually all children with minor defects survive into adulthood. Although exercise capacity may be limited, most lead normal or close to normal lives. In more severe defects, physical development may be slow, but mental development is rarely affected.

Treating Heart Defects
Many defects are only minor defects and most of the others are correctable by surgery. When surgery is necessary, many medical treatments are available to help the heart work properly. Regular medical follow-up is usually required.
 
Other cautions:
Bacterial endocarditis (BE) is an infection caused by bacteria that enter the bloodstream and settle in the heart lining, a heart valve or a blood vessel. Although BE is uncommon, a child with a heart defect has a greater risk of developing it. Thus, prevention is important - the child should be given antibiotics an hour or two before surgery or any dental procedures.

This is one in a series of brochures. For the full series and more heart smart information call the Heart Mark diet line on 0860 223 222 or visit www.heartfoundation.co.za.