One or more defects of the heart that are present at birth
- Present at birth
- Use of certain drugs and alcohol during pregnancy are risk factors
- Genetics and gender as risk factors depend on the type
The heart is a complex organ that can develop abnormally in a fetus, leading to defects that affect a baby from birth (congenital heart defects). Congenital heart disease affects about 4–9 in 1,000 babies and is one of the most common birth defects. Many of these abnormalities disappear naturally as the baby grows, but more serious defects require complex corrective surgery.
Congenital heart disease may cause shortness of breath in affected children, which may inhibit their feeding, growth, and activity.
What are the causes?
In most cases, the cause of congenital heart disease is unknown. However, it can sometimes run in families, suggesting that a genetic factor may be involved. Heart defects at birth may also be associated with genetic disorders, such as Down’s syndrome. Exposure of the fetus to excessive alcohol or drugs such as the anticonvulsant phenytoin increases the risk of congenital heart disease. In early pregnancy, certain infections, such as rubella, in the mother can lead to fetal heart defects (see Congenital infections). More than 1 in 10 babies with congenital heart disease are also found to have a defect elsewhere in the body, commonly in the digestive tract.
What are the types?
Most types of congenital heart disease affect only one part of the heart or one of the major blood vessels, such as the aorta, connected to the heart. Less commonly, several parts of the heart or more than one blood vessel are affected. These multiple heart defects are more serious and can be life-threatening.
The most common type of congenital heart abnormality is a septal defect, also known as a hole in the heart. In this defect, there is a hole in the septum (the inner wall that divides the heart) either between the two lower chambers (ventriculoseptal defect, pictured left) or alternatively between the two upper chambers (atrioseptal defect). In both cases, some oxygen-rich blood passes from the left side to the right side of the heart and is sent back to the lungs instead of going around the body. About 1 in 3 cases of congenital heart disease is due to a ventriculoseptal defect, which is often small and may close naturally. About 1 in 4 cases of congenital heart disease is caused by an atrioseptal defect, which usually produces few symptoms but is likely to require surgical treatment. Both septal defects are common in children with Down’s syndrome.
Patent ductus arteriosus
The ductus arteriosus is a small blood vessel that connects the pulmonary artery to the aorta in the fetus so that blood bypasses the lungs. If this vessel fails to close up soon after birth, normal circulation is prevented. This disorder is often found in premature babies.
Coarctation of the aorta
In this congenital heart disorder there is a narrowing of an area in the aorta, which restricts the flow of blood to the lower part of the body. As a result, the heart muscle works harder to compensate, and the pressure of blood in the upper part of the body is raised. The disorder requires surgical treatment. Children with coarctation of the aorta may additionally have an abnormality of one or more of the four heart valves.
Any of the four heart valves may develop abnormally. The most common valve disorder is pulmonary stenosis. In this condition, the pulmonary valve, which opens to allow blood to flow from the right ventricle into the pulmonary artery, is narrowed so that blood flow is restricted. Defects of the aortic valve, which opens to allow blood to flow from the left ventricle into the aorta, are less common.
Sometimes, several heart defects occur together. In addition to placing extra strain on the heart, the defects usually prevent blood from passing through the lungs normally so that blood oxygen levels become very low. Tissues throughout the body may then become oxygen-starved. The most common multiple defect is Fallot’s tetralogy, in which four heart abnormalities occur together. These consist of a ventriculoseptal defect, obstruction to blood flow from the right ventricle (known as right ventricular outflow obstruction), a displaced aorta, and a thickened right ventricle. Another type of multiple defect is hypoplastic left heart syndrome, in which the chambers and valves on the left side of the heart are underdeveloped. This was once a fatal condition but can now sometimes be treated. A rarer multiple defect involves reversal of the positions of the aorta and the pulmonary artery.
What are the symptoms?
Minor congenital heart defects may not cause symptoms. When symptoms do occur, they vary depending on the severity and type of the heart defect. The symptoms of all types of congenital heart disease may include:
Shortness of breath, leading to difficulty in feeding and sweating.
Slow weight gain and growth.
Symptoms of severe heart defects may develop suddenly in the first weeks of life. If there are low levels of oxygen in the blood, the tongue and lips may appear bluish in colour. Children with heart defects may be susceptible to chest infections and are at increased risk of infection of the lining of the heart (see Infective endocarditis), especially after surgery or dental treatment. Over a period of several years, congenital heart defects may lead to irreversible damage to the lungs (see Pulmonary hypertension).
How is it diagnosed?
In some cases, congenital heart disease is diagnosed during routine ultrasound scanning in pregnancy. Otherwise, defects may be found after birth when symptoms develop or during a routine examination. The doctor may hear a sound (heart murmur) caused by turbulent blood flow while listening to your child’s heart. Although many heart murmurs are normal, the doctor is likely to arrange for an ECG, which monitors the electrical activity of the heart. Your child may also have the imaging technique echocardiography, which is used to assess the structure and function of the heart.
What is the treatment?
Many heart defects correct themselves or need no treatment. Only about 1 in 3 children requires surgery. Affected children are usually monitored throughout childhood and, if necessary, surgery is performed when the child is older and the operation easier. Rarely, an emergency operation is necessary to save a young baby’s life. A heart transplant is now a possibility for children who have multiple heart defects. Chest infections need to be treated promptly, and, if the child has dental treatment or surgery, antibiotics may be necessary to prevent infection of the lining of the heart. Some children will need drugs, such as diuretics, to control the symptoms of a heart defect.
What is the prognosis?
The outlook depends on the type of heart defect and its severity. Septal defects either close naturally or are corrected surgically. As a result of surgical advances over the last 20 years, even very severe defects can often be corrected, and many severely affected children are leading normal, active lives.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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