Unknown: Congenital Heart Disease
Unknown: Congenital Heart Disease
Congenital heart disease, also known as congenital heart defect or CHD, refers to problems or abnormalities in the structure of a baby's heart that are present at birth. These abnormalities can affect the heart muscle itself, the valves inside the heart, or the arteries and veins supplying the heart. The defects can affect the baby's health by slowing down the flow of blood, blocking the blood flow completely, or causing the blood to flow in the wrong direction. Congenital heart defects are the most common type of major birth defect; they range from minor problems that do not cause any obvious symptoms to life-threatening abnormalities.
Doctors divide congenital heart defects into two major categories depending on whether they cause a bluish-gray discoloration of the mouth, lips, and nail beds called cyanosis. Cyanosis occurs when the blood flowing through the blood vessels close to the skin surface is not carrying enough oxygen to give the lips or mouth their normal pinkish color. Some congenital heart defects lead to cyanosis while others are called noncyanotic defects because they do not produce this skin discoloration.
The signs and symptoms of congenital heart defects vary greatly in severity. Most of these defects produce a heart murmur—a characteristic whispering sound that the doctor can hear through a stethoscope. Some defects, however, may produce no other noticeable symptoms, while others may lead to shortness of breath, cyanosis, chest pain, sweating, frequent respiratory infections, underdeveloped limbs and muscles, poor feeding, or slowed growth.
Cyanotic congenital heart defects include:
- Tetralogy of Fallot. This is the most common cyanotic heart defect, accounting for 5–7 percent of all congenital heart defects. It is named for a French doctor who described it in 1888. Tetralogy means that this defect involves four different interrelated abnormalities: a hole between the two bottom chambers (ventricles) of the heart; an aorta in an abnormal location; a narrowing of a heart valve that prevents normal blood outflow from the right ventricle; and a larger than normal right ventricle.
- Transposition of the great vessels (TGA). TGA is a defect in which the aorta and the pulmonary artery (the artery that carries blood from the heart to the lungs) are switched, so that the heart receives blood that has not been oxygenated in the lungs and sends this oxygen-poor blood out to the rest of the body.
- Persistent truncus arteriosus. The truncus arteriosus is a structure found in human embryos that normally divides to form the aorta and the pulmonary artery prior to birth. If that division does not occur, the baby is born with a single large blood vessel instead of two normal arteries and can develop heart failure within a few weeks after birth.
- Tricuspid atresia. Tricuspid atresia is a heart defect in which the valve between the two chambers on the right side of the heart does not open. In addition, the heart's right ventricle is unusually small.
Noncyanotic congenital heart defects include:
- Ventricular septal defect (VSD). A VSD is a hole in the wall of tissue that normally divides the two lower chambers of the heart. It is the most common type of CHD, accounting for 30–60 percent of all CHDs.
- Atrial septal defect (ASD). An ASD is a hole in the tissue that normally separates the two upper chambers of the heart.
- Patent ductus arteriosus (PDA). The ductus arteriosus is a temporary passageway that connects the pulmonary artery and the aorta that usually closes within a few hours or days after the baby is born. Patent means that the passageway remains open. PDAs are more common in babies born prematurely than in full-term babies.
- Aortic stenosis. Aortic stenosis is a defect in which the aortic valve—a heart valve that controls the flow of blood from the left ventricle to the aorta—is narrower than normal and slows down the flow of blood out of the heart.
- Coarctation of the aorta (COA). In COA, a portion of the aorta is abnormally narrow, reducing the amount of blood that the heart can pump to the rest of the body.
Congenital heart disease is one of the most common birth defects, occurring in eight out of every 1,000 newborns in the United States, or about 40,000 babies in an average year according to the March of Dimes. Most congenital heart defects either heal by themselves or respond well to treatment; however, 4,000 babies with CHDs will not survive their first year of life. Twice as many children die each year from CHDs than from all types of children's cancers combined.
Risk factors for congenital heart disease include:
- Premature birth.
- Family history of CHD. Having one baby with a CHD increases the risk of having a second child with a heart defect by a factor of five. If the baby's mother has a CHD, the risk for a child to be born with CHD ranges 2.5–18 percent, with an average risk of 6.7 percent. If the father has CHD, the risk for a child to be born with CHD ranges 1.5–3 percent.
- Rubella in the mother during early pregnancy.
- Mother's abuse of alcohol or drugs during pregnancy.
- Chronic diseases in the mother, particularly diabetes and lupus.
- Mother's use of certain antiseizure medications.
Most cases of congenital heart disease (85–90 percent) do not have a known cause. Some known causes of CHDs include:
- Genetic disorders involving parts of a chromosome (5–8 percent of CHDs): these include Down syndrome, Edwards syndrome, Patau syndrome, and Turner syndrome.
- Single-gene defects (3–5 percent): Marfan syndrome is the most common single-gene disorder linked to CHDs.
- Environmental factors (2 percent).
Symptoms of CHDs vary somewhat depending on the specific heart defect but may include:
- Heart murmur
- Rapid breathing
- Lack of appetite and poor feeding
- Failure to gain weight
- Sweating during feedings
- Weak pulse
Some CHDs can be detected during pregnancy or during the baby's first physical examination when the doctor listens to the heart and looks for
cyanosis, rapid breathing, a weak pulse, or indications of heart failure. Small heart defects may not be detected until the child is older or even until the adult years.
Specific tests that can be done to evaluate the type and severity of a congenital heart defect include:
- Echocardiogram. This is a test that uses sound waves to produce an image of the baby's heart. It can be done during the fourth or fifth month of pregnancy to plan treatment for the baby after it is born. An echocardiogram can also be performed to diagnose babies after birth.
- Chest x ray. This test may be done to see whether the baby's lungs are normal as well as whether its heart is abnormally large.
- Electrocardiogram (ECG or EKG). An ECG is a tracing of the heart's electrical activity. It shows the speed of the heartbeat and whether the heart rhythm is regular or irregular.
- Pulse oximetry. This test uses a sensor placed on the baby'sfingertip or toe to measure how much oxygen is carried in the blood.
- Cardiac catheterization. A catheter is a long thin tube that is passed through a vein in the baby's neck, arm, or upper thigh to reach the heart. A special dye that can be seen on x ray is injected through the catheter into the blood vessels or the heart itself. This test allows the doctor to trace the path and the direction that the blood takes through the chambers and major blood vessels of the heart.
Treatment of congenital heart disease varies depending on the type of defect and its severity. Some small defects may not require any specific treatment. In some cases the doctor may prescribe medications—usually diuretics to help the baby eliminate excess water through the urine; or digoxin, a drug that helps the heart muscle contract with greater force, thus strengthening the heart.
Some congenital heart defects require one or more surgical procedures to repair the abnormalities. Atrial septal defects and aortic valve stenosis can be repaired by using a catheter. The surgeon inserts the catheter through a vein and threads it into the heart. A small device can be positioned through the catheter to fill an ASD, or a balloon can be threaded through the catheter
to open a partially closed valve. The balloon can then be collapsed and the catheter removed.
Open-heart surgery is usually necessary to replace a badly damaged valve; to close large holes in the septa between the ventricles or atria; or to repair a complicated defect like tetralogy of Fallot. In a few very rare cases, the baby may need a heart transplant if there are multiple defects that are too severe or complicated to repair by surgery.
The prognosis of congenital heart disease varies. About 10 percent of infants with CHDs die during their first year of life. Advances in surgery since the 1980s mean that most children with congenital heart disease can live into adulthood and enjoy normal and productive lives. Many do not need any special care, although some will need periodic checkups with a heart specialist as well as with their pediatrician as they grow older.
Most CHDs cannot be prevented because their cause is still unknown. Some can be prevented, however, by the following measures:
- Vaccination against rubella before getting pregnant.
- Avoiding alcohol and drugs during pregnancy.
- Consulting a genetic counselor before becoming pregnant if there is a family history of CHD.
- Consulting a doctor before becoming pregnant if the mother is being treated for diabetes, lupus, or seizure disorder.
Congenital heart disease is not likely to become more common in the general population in the near future. Research in the field is directed toward a better understanding of the genetic factors that may be involved in CHD, and closer study of the development of a baby's heart during pregnancy. This information in turn may guide the invention of new or improved surgical techniques to treat congenital heart defects as early as possible, perhaps even before the baby's birth.
WORDS TO KNOW
Aorta : The large artery that carries blood away from the heart to be distributed to the rest of the body.
Atrium (plural, atria) : One of the two upper chambers of the heart.
Congenital : Present at birth.
Cyanosis : A blue discoloration of the lips, inside of the mouth, and nail beds caused by lack of oxygen in the blood vessels near the skin surface.
Embryo : The medical term for an unborn baby from the time of conception to the end of its first eight weeks of life.
Patent : The medical term for open or unobstructed.
Septum (plural, septa) : A partition that separates two cavities or chambers in the body.
Stenosis : The medical term for abnormal narrowing of the opening of a blood vessel.
Ventricle : One of the two lower chambers of the heart.
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Children's Hospital Boston. Congenital Heart Defects—Causes. Available online at http://www.childrenshospital.org/az/Site2116/mainpageS2116P0.html (updated December 2006; accessed on September 30, 2008).
March of Dimes. Fact Sheet: Congenital Heart Defects. Available online at http://www.marchofdimes.com/professionals/14332_1212.asp (updated May 2008; accessed on September 30, 2008).
National Heart, Lung, and Blood Institute (NHLBI). What Are Congenital Heart Defects? Available online at http://www.nhlbi.nih.gov/health/dci/Diseases/chd/chd_what.html (updated December 2007; accessed on September 30, 2008).
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