Congenital Heart Defect

A congenital heart defect is a structural problem (or defect) in the heart that is present at birth. A baby's heart begins to develop shortly after conception. During development, structural defects can occur. These defects can involve the walls of the heart, the valves of the heart, and the arteries and veins near the heart. Congenital heart defects can disrupt the normal flow of blood through the heart. The blood flow can:

• Slow down
• Go in the wrong direction or to the wrong place
• Be blocked completely

Congenital heart defect is the most common type of major birth defect. Each year, more than 30,000 babies in the United States are born with congenital heart defects.

Types

There are many types of congenital heart defects. They include:

• Abnormal passages in the heart or between blood vessels
• Problems with the heart valves
• Problems with the placement or development of blood vessels near the heart
• Problems with development of the heart itself

Some of these problems are described below.

Abnormal passages in the heart or between blood vessels

• Atrial septal defect (ASD) is a hole in the wall that separates the upper chambers (atria) of the heart. This causes blood to leak from one atrium to the other.
• Ventricular septal defect (VSD) is a hole in the wall that separates the lower chambers (ventricles) of the heart. This causes blood to leak from one ventricle to the other.
• Atrioventricular septal defect (AVSD) includes an ASD, VSD, and abnormal development of the atrioventricular valves (tricuspid and mitral). This causes blood to flow abnormally inside the heart. An AVSD is also known as an atrioventricular canal defect.
• Patent ductus arteriosus (PDA) is a persistent connection between the aorta and the pulmonary artery. This connection is called the ductus arteriosus and is normally present before birth. In most babies, the vessel closes within a few hours or days after birth. In some children, the vessel fails to close, resulting in PDA.

Problems with the heart valves

Congenital heart defects can involve any of the valves and include the following types of problems:

• Stenosis. The valve opening is narrow and does not open completely.
• Atresia. The valve does not form, so there is no opening for blood to pass from one chamber to another.
• Regurgitation. The valve does not close completely, so blood can leak back through the valve.

Examples of particular heart valve problems include:

• Aortic valve stenosis is a narrowing of the aortic valve in the heart that causes it to open incompletely. This can reduce blood flow to the body.
• Pulmonary valve atresia is a defect in which a solid sheet of tissue forms in place of the pulmonary valve. This prevents blood in the right side of the heart from traveling normally to the lungs to pick up oxygen.
• Pulmonary valve stenosis is a narrowing of the pulmonary valve. The narrowing slows the flow of blood from the right side of the heart to the lungs. The heart must pump harder to push blood through the smaller opening.
• Tricuspid valve atresia is a defect in which a solid sheet of tissue forms in place of the tricuspid valve. Without the tricuspid valve, blood entering the right atrium cannot travel normally to the right ventricle and then to the lungs to pick up oxygen.
• Ebstein's anomaly is a defect in which the tricuspid valve is both displaced and abnormally formed. The valve leaks and allows blood to flow back into the right atrium instead of to the lungs to pick up oxygen.

Problems with placement or development of blood vessels near the heart

• Transposition of the great vessels is a defect in which the location of the "great vessels" (the aorta and pulmonary artery) coming off the heart is switched. The aorta comes off the right ventricle instead of the left ventricle. The pulmonary artery comes off the left ventricle instead of the right ventricle. Therefore, blood without oxygen is continually pumped to the body, instead of blood with oxygen.
• Tetralogy of Fallot is a combination of four defects:
  • Pulmonary valve stenosis is the narrowing of the pulmonary valve. The narrowing slows the flow of blood from the right ventricle to the lungs.
  • VSD is a hole in the wall that separates the left and right ventricles.
  • Overriding aorta is a defect in which the aorta is positioned between the left and right ventricles, over the VSD.
  • Right ventricular hypertrophy is the thickening of the right ventricle. The thickening is caused by the heart having to work harder because of the other defects.

• Truncus arteriosus is a defect of the great vessels. The aorta and pulmonary artery do not form as separate arteries. Instead, a large artery, called the truncus, comes from the heart. As the truncus leaves the heart, it may branch into arteries that carry blood to the body and to the lungs.
• Coarctation of the aorta is a narrowing of the aorta. It slows or blocks the flow of blood from the heart to the body.
• Anomalous pulmonary venous return is a defect in which one or more of the four pulmonary veins, which normally return oxygen-rich blood from the lungs to the heart, return to the wrong chamber in the heart.

Problems with development of the heart

• Hypoplastic left heart syndrome is a combination of defects in which the left side of the heart does not develop properly. Defects usually include mitral atresia, aortic atresia, and a tiny left ventricle.
  • Mitral atresia occurs when a solid sheet of tissue forms instead of the mitral valve, which separates the left atrium and the left ventricle.
  • Aortic atresia occurs when a solid sheet of tissue forms instead of the aortic valve, which separates the left ventricle from the aorta.
• Single ventricle describes a group of heart defects in which only one ventricle is present instead of two. It can be a single right or a single left ventricle. The other ventricle is usually absent or very tiny. Hypoplastic left heart syndrome is an example of a single ventricle defect.

Symptoms

The most common signs and symptoms of congenital heart defects are:

• A heart murmur
• A bluish tint to skin, lips, and fingernails ("blue baby")
• Fast breathing
• Shortness of breath
• Poor feeding, especially in infants because they tire easily while nursing
• Poor weight gain in infants
• Tiring easily during exercise or activity (older children)

The signs and symptoms that a child has depend on:

• The number and types of defects
• The severity of the defect

Some infants and children have no signs or symptoms. Others have severe or life-threatening symptoms.

Many types of congenital heart defects cause the heart to work harder than it should. This stresses the heart and can lead to heart failure, causing the heart muscle to weaken and the heart to enlarge.

Diagnosis

Doctors usually diagnose congenital heart defects during pregnancy or within the first few months after birth. Some children with less severe defects are not diagnosed until they are older and more demands are put on their hearts. Others are not diagnosed until they are adults.

If your child's doctor suspects a congenital heart defect, he or she will refer your child to a specialist who treats heart problems in children. The specialist, a pediatric cardiologist, will take a family and medical history, do a physical exam, and order several tests.

Physical Exam

During the physical exam, the doctor:

• Listens to your child's heart with a stethoscope for a heart murmur
• Looks for signs of illness or physical problems, such as bluish color of skin and lips, shortness of breath, rapid breathing, and delayed growth
• Listens to your child's lungs

Tests

An echocardiogram, which is harmless and painless, uses sound waves to create a moving picture of your child's heart. During an echocardiogram, reflected sound waves outline the heart's structure completely. The test allows the doctor to clearly see any problem with the way the heart is formed or the way it's working. An echocardiogram is the most important test available to your child's cardiologist to both diagnose a heart problem and follow the problem over time. In children with congenital heart defects, an echocardiogram will outline each problem with the heart's structure and show how the heart is reacting to these problems. The echocardiogram will help your child's cardiologist to know if and when treatment is needed.

During pregnancy, if your doctor suspects that your baby has a congenital heart defect, a special test called a fetal echocardiogram can be done. This test uses sound waves to create a picture of the baby's heart while the baby is still in the womb. The test is usually done during the fifth month of pregnancy. If your child is diagnosed with a congenital heart defect before birth, your doctor can plan treatment before the baby is born.

Other tests used to help diagnose congenital heart defects include:

• EKG (electrocardiogram). An EKG test measures the rate and regularity of your child's heartbeat.
• Chest x ray. A chest x ray takes a picture of your child's heart and lungs. It can show if the heart is enlarged or if there is fluid in the lungs.
• Pulse oximetry. This test uses a sensor to see how well your child's lungs are passing oxygen to the blood and whether there is any mixing of oxygen-rich and oxygen-poor blood. The sensor is placed on the child's fingertip or toe (like an adhesive bandage). A small computer unit shows the amount of oxygen in the blood through the skin. The test does not hurt.
• Cardiac catheterization. In this test, a thin flexible tube is passed through an artery or vein at the upper thigh (groin) or in the arm to reach the heart. With the assistance of x rays, the doctor can then see your child's blood vessels and heart. The catheter also measures the pressure inside the heart and blood vessels and can determine if blood is mixing between the two sides of the heart. Sometimes, a dye that can be seen by x ray is injected into the heart. This enables the doctor to see the flow of blood throughout the heart and blood vessels.

Causes

Doctors do not know what causes most cases of congenital heart defects. Heredity may play a role. In rare cases, more than one child in a family is born with a heart defect. Also, parents who have a congenital heart defect may be more likely than other parents to have a child with the condition.

Babies who have certain other birth defects, such as Down syndrome, are also more likely to have congenital heart defects.

Other factors that raise the risk for congenital heart defects are:

• Having viral infections, such as German measles (rubella), during pregnancy
• Having diabetes
• Taking some types of prescription or over-the-counter medicines during pregnancy
• Being repeatedly exposed to some chemicals or x rays during pregnancy
• Using alcohol or street drugs during pregnancy

Reference:

National Heart, Lung, and Blood Institute, USA.