Congenital heart disease includes a number of birth defects of the heart, the blood ves sels that feed into it, or the vessels that carry blood out from it. The causes of most of these defects are unknown. Genetic factors play some role, and the risk of a child having a heart defect increases if a parent or sibling has one. In one large study, 12 percent of the cases of congenital heart malformations were related to a chromosomal defect such as Down syndrome (see Down Syndrome in this chapter), and 8 percent occurred in infants who had multiple congenital abnormalities (birth defects). Some children with congenital heart disease have an identifiable single gene defect, such as Marfan syndrome, a hereditary connective tissue disorder.
About 3 percent of cases are associated with a disease the mother had during pregnancy, including diabetes, lupus, rubella (German measles), or phenylketonuria (PKU), a disorder involving the enzyme that processes the amino acid phenylalanine. Certain drugs taken during pregnancy, such as lithium, ethanol (alcohol), warfarin (a blood thinner), thalidomide, antimetabo-lites (such as some cancer chemotherapy drugs), and anticonvulsant (seizure) medications are also associated with an increased incidence of congenital heart defects.
The most common defects are holes in the walls that separate the heart into the left and right sides. Atrial septal defects occur between the upper chambers of the heart, which receive the blood entering the heart. These account for 6 to 8 percent of all heart defects. Ventricular septal defects occur between the lower chambers, which pump blood out of the heart to the lungs and the rest of the body. These represent about 25 to 30 percent of all heart defects. In both of these abnormalities, some of the blood returning to the heart from the lungs is not pumped out to the body normally—it is sent back to the lungs instead.
As a result, the amount of blood in the lungs' blood vessels increases, causing extra work for the heart and sometimes problems in the lungs.
A third common defect is patent ductus arteriosus, which occurs in about 7 percent of infants with heart defects. The ductus arteriosus is a blood vessel connecting the aorta, the large artery that carries oxygen-rich blood to the body, and the pulmonary artery, the artery that carries oxygen-depleted blood to the lungs. The ductus allows blood to bypass the lungs in the fetus, because the fetus gets oxygen from the placenta and doesn't breathe air. However, at birth blood must flow to the lungs to receive oxygen. Normally, the ductus closes within a day or two after birth. But if the ductus remains open, blood intended for the rest of the body may return to the lungs, sometimes causing abnormal stress on the lungs and heart.
Narrowing (stenosis) of valves (one-way openings into the heart that keep the blood from flowing backward) is also not uncommon. Valves that are narrowed do not permit normal blood flow.
Symptoms and Diagnosis Some children may show signs of a heart defect in the first few days after birth; others may seem completely healthy until they are a few weeks old or until later in childhood. Generally, signs of significant heart disease in infants may include rapid breathing; shortness of breath; blueness of the lips, tongue, and under the nails; tiring out easily with feedings; and failure to gain weight normally.
Children with large ventricular septal defects are at risk for repeated respiratory infections, other lung complications, and heart failure.
Children with atrial septal defects usually have less obvious symptoms.
There are usually no symptoms with a small patent ductus arteriosus, but a large defect will lead to heart failure and failure to grow normally.
The doctor will listen to the child's chest with a stethoscope to hear if there is an abnormal sound, called a heart murmur, that might indicate blood is not flowing through the heart and blood vessels properly. It is important to note that some heart murmurs may be present at birth and disappear with time, and others may not appear until weeks or more after birth. Most heart murmurs are benign ("innocent") and do not mean there is heart disease or affect a child's health. The doctor will also feel for pulses to see if blood is being circulated through all parts of the body normally.
If the child's symptoms or if the findings from a physical examination are of concern to the doctor, he may order further evaluation. This may include blood tests, a chest X-ray, electrocardiogram (EKG), or echo-cardiogram (ultrasound imaging study of the heart).
If a more significant heart defect is suspected, particularly of a type requiring surgical correction, the heart specialist (usually a pediatric cardiologist) may perform a cardiac catheterization study. In this procedure, a thin tube is inserted into a blood vessel in the child's leg or arm and then passed into the heart. Doctors can then measure the pressures and oxygen content of the blood in various chambers of the heart and large blood vessels, and also inject dye that can be seen on X-rays to get a detailed look at the pattern of blood flow and the structure of the child's heart.
Treatment and Outlook Treatment for heart defects depends on the type and severity. Some heart defects, such as small ventricular septal defects, may resolve on their own, requiring nothing more than careful follow-up and watchful waiting.
Certain forms of congenital heart disease can actually be treated by installing patches onto holes in the heart through a heart catheterization procedure or widening narrowed heart valves by pulling a balloon on the tip of the catheter through the obstructed area; these procedures can avoid or delay the need for open heart surgery.
Other heart defects may require surgical correction, with timing of the procedures and techniques used depending on the severity and type of the defect.
Before, and sometimes after, surgery is performed to treat a heart defect, a variety of medications may be used to support the child's heart function or control other problems associated with the child's condition.
Most children with congenital heart defects are at greater risk for developing a serious bacterial infection of the lining of the heart or heart valves. This is of particular concern with certain procedures, such as some types of dental work, that cause germs to be shed into the child's bloodstream where they can be carried to the heart. Parents should speak to their child's doctors about the need for antibiotic treatment before such procedures to prevent infection of the heart.
The long-term outlook for children with congenital heart disease varies widely depending on the type and severity of the defect, treatments available, and other health problems the child may have.
Prevention and Prenatal Testing The heart of the developing fetus is most susceptible to damage during the first three to seven weeks of pregnancy. Because more than half of all pregnancies are unplanned and the fetal heart may suffer injury before a woman knows she is pregnant, careful attention to risk reduction is important in all women who are planning to become pregnant. This includes avoiding drinking alcohol and taking certain medications. Before getting pregnant, a woman should discuss with her doctor what medications are safe for her to take during pregnancy. If she has a chronic disease such as diabetes, she should discuss with her doctor the best way to manage it both before and during pregnancy. Rubella (German measles) also puts a woman at risk of having a baby with a heart defect. A woman planning a pregnancy should be sure that she has immunity against rubella—if she doesn't, she should be vaccinated. However, it is recommended that a woman should not become pregnant for three months after being vaccinated, and pregnant women should not be given live rubella virus vaccine.
Parents who have a child with congenital heart disease and who are planning another pregnancy may wish to seek genetic counseling about the risk of congenital heart disease occurring in subsequent children.
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