Diseases & Conditions


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Heart Defects


One of 120 babies is born with a heart defect. Some are severe, but many are not. Defects may involve abnormal formation of the heart's walls or valves or of the blood vessels that enter or leave the heart.

Blood flow is different in the fetus than in children and adults. In children and adults, all blood returning to the heart (venous blood) goes through the right atrium and then through the right ventricle to the pulmonary artery, and from there it enters the lungs. In the lungs, the blood picks up oxygen from the air sacs (alveoli) and also releases carbon dioxide (see Biology of the Lungs and Airways: Exchanging Oxygen and Carbon Dioxide ). The blood then returns from the lungs to the left atrium and left ventricle and from there it is pumped out of the heart to the body (arterial blood) through a large artery called the aorta. However, because there is no air to breathe before birth, a fetus uses oxygen obtained from the mother's blood through the placenta. Because the fetus does not breathe, only a small amount of blood needs to go through the lungs, so the path by which blood circulates through the heart and lungs is different in the fetus.

Before birth, much of the venous blood coming to the right side of the heart bypasses the lungs and mixes in two different places with blood that has already traveled to the lungs. Such mixing occurs through the foramen ovale, a hole between the right and left atria. Mixing also occurs through the ductus arteriosus, a blood vessel connecting the pulmonary artery and the aorta. In the fetus, because blood arriving at the heart has already received oxygen from the placenta. Both venous blood and arterial blood contain oxygen, so mixing arterial blood and venous blood does not affect how much oxygen gets pumped to the body. After birth, however, such mixing would severely limit the amount of oxygen in the blood, so the foramen ovale and ductus arteriosus normally close within days to a couple of weeks after birth.

Normal Circulation in a Fetus

Blood flow through the heart in a fetus differs from that in children and adults. In children and adults, blood picks up oxygen in the lungs. But in a fetus, the blood that enters the heart already contains oxygen, supplied from the mother by the placenta. Only a small amount of blood goes through the lungs (which do not contain air). The rest of the blood bypasses the lungs through two structures: the foramen ovale, a hole between the right and left atria, and the ductus arteriosus, a blood vessel that connects the pulmonary artery and the aorta. Normally, these two structures close soon after birth.

Abnormally formed hearts alter the normal blood flow to the lungs and body. Either the flow of blood gets re-routed (shunted) or a defective heart valve or a blood vessel blocks the flow of blood.

Shunting can cause oxygen-poor blood to mix with oxygen-rich blood that is pumped to the body tissues (right-to-left shunt). The more oxygen-poor blood (which is blue) that flows to the body, the bluer the body appears, particularly the skin and lips. Many heart defects are characterized by a bluish discoloration of the skin (called cyanosis); cyanosis indicates that not enough oxygen-rich blood is reaching the tissues where it is needed.

Shunting can also mix oxygen-rich blood, which is pumped under high pressures, with oxygen-poor blood being pumped through the pulmonary artery to the lungs (left-to-right shunt). Shunting makes the circulation inefficient and increases the pressure in the pulmonary artery. The high pressure damages the pulmonary artery and lungs. The shunt also eventually leads to an insufficient amount of blood being pumped to the body (heart failure).

In heart failure, blood also backs up, often in the lungs. Heart failure can also develop when the heart pumps too weakly (for example, when a baby is born with a weak heart muscle) or when blood is blocked from flowing to the baby's body.

Blockages may develop in the valves of the heart or in the blood vessels leading away from the heart. Blood may be impeded from flowing to the lungs because of narrowing of the pulmonary valve (pulmonary valve stenosis) or narrowing within the pulmonary artery itself (pulmonary artery stenosis). Blood may be impeded from flowing through the aorta to the body because of narrowing of the aortic valve (aortic valve stenosis) or blockage within the aorta itself (coarctation of the aorta).

Symptoms and Diagnosis

Often, heart defects produce few or no symptoms and are not detectable even during a physical examination of the child. Some mild defects produce symptoms only later in life. However, many heart defects do result in symptoms during childhood. Because oxygen-rich blood is necessary for normal growth, development, and activity, infants and children with heart defects may fail to grow or gain weight normally. They may not be able to exercise fully. In more severe cases, cyanosis may develop, and breathing or eating may be difficult. Abnormal blood flow through the heart usually produces an abnormal sound (murmur) that can be heard using a stethoscope; however, the vast majority of heart murmurs that occur during childhood are not caused by heart defects and are not indicative of any problems. Heart failure makes the heart beat rapidly and often causes fluid to collect in the lungs or liver. Some congenital heart defects (such as a hole in the atrium [patent foramen ovale]) increase the risk that a blood clot will form and block an artery in the brain, leading to a stroke.

Many heart defects can be diagnosed before birth by using ultrasound. After birth, heart defects are suspected when symptoms develop or when particular heart murmurs are heard.

Diagnosing heart defects in children involves the same techniques used for diagnosing heart problems in adults (see Symptoms and Diagnosis of Heart and Blood Vessel Disorders: Introduction ). A doctor may be able to diagnose the defect after asking the family specific questions and performing a physical examination, electrocardiography (ECG), and a chest x-ray. Ultrasound (echocardiography) is used to diagnose almost all of the specific defects. Cardiac catheterization often can show small abnormalities that are not detected with echocardiography or can further illuminate the details of the abnormality.

Treatment

Many significant heart defects are effectively repaired with open-heart surgery. When to perform the operation depends on the specific defect, its symptoms, and severity. For example, it may be better to postpone surgery until the child is a little older. However, severe symptoms resulting from a heart defect are most effectively relieved with immediate surgery.

A narrowing can sometimes be relieved by passing a thin tube (catheter) through a blood vessel in the arm or leg into the narrowed area. A balloon attached to the catheter is inflated and widens the narrowing, usually in a valve (a procedure called balloon valvuloplasty) or blood vessel (a procedure called balloon angioplasty—see Coronary Artery Disease: Percutaneous Coronary Intervention ). These balloon procedures spare the child from general anesthesia and open-heart surgery. However, balloon procedures are not usually as effective as surgery.

If the aorta or pulmonary artery is severely blocked, a temporary shunt can sometimes be created to keep an adequate amount of blood flowing. A shunt can be created with a catheter balloon (for example, between the right and left atria—balloon septostomy). Or drugs such as prostaglandin can be given to keep the ductus arteriosus open, shunting blood between the aorta and pulmonary artery. In rare cases, when no other treatment helps, a heart transplant is performed, but the lack of donor hearts limits the availability of this procedure.

Most children who have significant heart defects are at increased risk for developing life-threatening bacterial infections of the heart and its valves (endocarditis). They need to take antibiotics before certain treatments and procedures (see Infective Endocarditis ).

Patent Ductus Arteriosus

In patent ductus arteriosus, the blood vessel connecting the pulmonary artery and the aorta (ductus arteriosus) fails to close as it usually does within the first 2 weeks after birth.

In patent ductus arteriosus, a left-to-right shunt of blood from the aorta back into the pulmonary artery causes extra blood flow into the lungs, and high blood pressure in the lungs may damage the lung tissue. Premature newborns are especially susceptible to patent ductus arteriosus and lung damage.

Patent Ductus Arteriosus: Failure to Close

The ductus arteriosus is a blood vessel that connects the pulmonary artery and the aorta. In the fetus, it enables blood to bypass the lungs. The fetus does not breathe air, and thus blood does not need to pass through the lungs to be oxygenated. After birth, blood does need to be oxygenated in the lungs, and normally, the ductus arteriosus closes quickly, usually within days up to 2 weeks. In patent ductus arteriosus, this connection does not close, allowing some oxygenated blood, intended for the body, to return to the lungs. As a result, the blood vessels in the lungs may be overloaded and the body may not receive enough oxygenated blood.

Most often, the defect causes no symptoms. When symptoms do occur, they are usually difficulty breathing or cyanosis, which may be present at birth or not for several weeks after birth. When the infant has no symptoms, doctors most often suspect the defect when they hear a heart murmur.

Indomethacin Some Trade Names INDOCIN , a drug that inhibits the production of chemicals called prostaglandins, closes the defect in 80% of infants. Indomethacin Some Trade Names INDOCIN is most effective if given within the first 10 days after birth and is more effective in premature newborns than in full-term newborns. If the defect does not close after several doses of indomethacin Some Trade Names INDOCIN , it is closed surgically.

Atrial and Ventricular Septal Defects

Atrial and ventricular septal defects are holes in the walls (septa) that separate the heart into the left and right sides.

Atrial septal defects are located between the heart's upper chambers (atria), which receive blood. Ventricular septal defects are located between the lower chambers (ventricles), which pump blood. These holes typically cause left-to-right shunting of blood. Many atrial septal defects close by themselves, especially in the first year of life; many ventricular septal defects close within the first 2 years.

Infants and most older children with atrial septal defects have no symptoms. However, children who have no symptoms but who do have a small shunt require annual echocardiography. In more severe cases, children may develop heart murmurs and fatigue and may have difficulty breathing. Rarely, the first sign of an atrial septal defect is a stroke. The symptoms caused by atrial septal defects increase as the child ages. For example, heart failure may develop during middle age.

Septal Defect: A Hole in the Heart's Wall

A septal defect is a hole in the wall (septum) that separates the heart into the left and right sides. Atrial septal defects are located between the heart's upper chambers (atria). Ventricular septal defects are located between the lower chambers (ventricles). In both types, some oxygenated blood, intended for the body, is shortcircuited. It is returned to the lungs rather than pumped to the rest of the body.

Ventricular septal defects can vary from small holes, which may cause a heart murmur but no symptoms and usually close by themselves, to larger holes that cause symptoms in infants. Significant ventricular septal defects usually cause more severe symptoms than atrial septal defects, because there is more shunting of blood. Recurrent lung infections and heart failure may develop. Because of the way lungs develop, shunting increases during the first 6 weeks after birth. Usually the murmur becomes louder, and symptoms, typically rapid breathing, sweating, and difficulty feeding, worsen. Echocardiography usually confirms the diagnosis. Mild symptoms of a ventricular septal defect may be treated with diuretics (such as furosemide Some Trade Names LASIX ) or drugs that decrease resistance to the flow of blood to the body (such as captopril Some Trade Names CAPOTEN ). If atrial and ventricular septal defects are large, do not close spontaneously during the first few years of life, or cause symptoms, they are usually closed surgically.

Tetralogy of Fallot

In tetralogy of Fallot, four specific heart defects occur together.

The defects are a large ventricular septal defect, displacement of the aorta that allows oxygen-poor blood to flow directly from the right ventricle to the aorta (causing a right-to-left shunt), a narrowing of the outflow passage from the right side of the heart, and a thickening of the wall of the right ventricle.

Tetralogy of Fallot: Four Defects

In infants with tetralogy of Fallot, the narrowed passage from the right ventricle restricts blood flow to the lungs. The restricted blood flow causes the oxygen-poor blood in the right ventricle to pass through the septal defect to the left ventricle and into the aorta (right-to-left shunt). The most important symptom is cyanosis, which can be mild or severe. Some infants have life-threatening attacks (hypercyanosis or "tet" spells), in which cyanosis suddenly worsens in response to activity, such as crying or having a bowel movement. The infant becomes very short of breath and may lose consciousness. Infants with tetralogy of Fallot usually have a heart murmur. Echocardiography confirms the diagnosis.

When an infant has a hypercyanotic spell, oxygen, morphine Some Trade Names MS CONTIN ORAMORPH , and beta-blockers (such as propranolol Some Trade Names INDERAL ) may provide quick relief. The infant may breathe more easily when the knees are close to the chest (knee-chest position). Giving intravenous fluids or a drug such as phenylephrine Some Trade Names NEO-SYNEPHRINE , both of which increase resistance to the flow of blood to the body, may be helpful. A doctor may give the infant propranolol Some Trade Names INDERAL to prevent future spells until corrective surgery can be performed. In infants who have tetralogy with complete blockage of outflow from the right side of the heart (pulmonary atresia) and who depend on an open ductus arteriosus for survival, giving a prostaglandin such as alprostadil Some Trade Names CAVERJECT PROSTIN VR to maintain an open ductus arteriosus can be lifesaving.

Infants with tetralogy of Fallot eventually need surgery. If symptoms are frequent or severe, surgery is performed in early infancy, but can be delayed until later in infancy if the child has few symptoms. To keep blood flowing to the lungs until corrective surgery can be performed, some doctors use less invasive procedures such as balloon valvulotomy, in which a long catheter with a balloon on its tip is passed through a vein into the heart. The balloon is inflated in the valve, widening the opening. During corrective surgery, the ventricular septal defect is closed, the narrowed passageway from the right ventricle and the narrowed pulmonary valve are widened, and any abnormal connections between the aorta and pulmonary artery are closed.

Transposition of the Great Arteries

Transposition of the great arteries is a reversal of the normal connections of the aorta and the pulmonary artery with the heart.

Oxygen-poor blood returning from the body flows from the right atrium to the right ventricle as usual, but then flows to the aorta and the body, bypassing the lungs. Oxygenated blood travels back and forth between the heart and lungs (from the lungs to the pulmonary vein, then left atrium and ventricle, then the pulmonary artery) but is not transported to the body. The body cannot survive without oxygen. However, infants with this defect may survive briefly after birth because the foramen ovale (a hole between the right and left atria) and the ductus arteriosus (a blood vessel connecting the pulmonary artery with the aorta (see Birth Defects: Patent Ductus Arteriosus ) are still open at birth. These openings allow oxygen-rich blood to mix with oxygen-poor blood, sometimes supplying enough oxygen to the body to keep the infant alive. Transposition of the great arteries is often accompanied by a ventricular septal defect.

Transposition of the great arteries usually results in severe cyanosis and difficulty breathing, beginning at birth. A doctor performs a physical examination, x-ray, electrocardiography, and echocardiography to confirm the diagnosis. Usually, surgery is performed within the first few days of life. Surgery consists of attaching the aorta and pulmonary artery to the appropriate ventricles and reimplanting the heart's coronary arteries in the aorta after the aorta is repositioned. Giving alprostadil Some Trade Names CAVERJECT PROSTIN VR or performing a balloon septostomy can shunt the blood, which can keep the infant alive until surgery can be performed.

Aortic Valve Stenosis

Aortic valve stenosis is a narrowing of the valve that opens to allow blood to flow from the left ventricle into the aorta and then to the body.

To propel blood through the narrowed aortic valve, the left ventricle must pump under very high pressures. Sometimes, not enough blood is pumped to supply the body with oxygenated blood.

Most children with aortic valve stenosis do not develop symptoms other than a heart murmur. In some older children, the defect causes fatigue, chest pain, shortness of breath, or fainting. In adolescents, severe aortic valve stenosis may lead to sudden death, presumably because of an erratic heart rhythm caused by poor blood flow through the coronary arteries to the heart. A few infants who have aortic valve stenosis develop irritability, an unnatural lack of color to the skin (pallor), low blood pressure, sweating, rapid heartbeat, and severe shortness of breath.

A doctor suspects aortic valve stenosis after detecting a particular murmur or if the child develops symptoms. Cardiac catheterization is often used to determine the severity of the narrowing.

For older children with severe narrowing or symptoms, the aortic valve must be replaced or widened. Usually the valve is opened surgically (using a procedure called balloon valvulotomy) or replaced with an artificial one. Children with an artificial valve must take an anticoagulant drug, such as warfarin Some Trade Names COUMADIN , to prevent blood clots from forming. Infants with heart failure must have emergency treatment, usually including drugs and emergency surgery or balloon valvoplasty.

Pulmonary Valve Stenosis

Pulmonary valve stenosis is a narrowing of the pulmonary valve, which opens to allow blood to flow from the right ventricle to the lungs.

In most children with pulmonary valve stenosis, the valve is mildly to moderately narrowed, making the right ventricle pump harder and at a higher pressure to propel blood through the valve. Severe narrowing increases pressure in the right ventricle and prevents almost any blood from reaching the lungs. When pressure in the right ventricle becomes extremely high, oxygen-poor blood is forced through abnormal paths (usually a hole in the atrial wall [atrial septal defect]) instead of the pulmonary artery, causing right-to-left shunting.

Most children with pulmonary valve stenosis have no symptoms other than a heart murmur. However, severe cyanosis or heart failure is possible. Moderate symptoms, such as difficulty breathing with exertion and fatigue, may develop as the child gets older. Echocardiography is done to confirm the diagnosis. Occasionally, cardiac catheterization is needed to assess the severity of the narrowing.

If the valve is moderately narrowed, it may be opened with balloon valvuloplasty. If the valve is not well formed, it can be surgically reconstructed.

Severe disease that causes cyanosis in newborns is treated by giving a prostaglandin such as alprostadil Some Trade Names CAVERJECT PROSTIN VR , which opens the ductus arteriosus, until a surgeon can create another way to open or bypass the pulmonary valve. For some of these newborns, more surgery is needed when they are older.

Coarctation of the Aorta

Coarctation of the aorta is a narrowing of the aorta, usually just before the point where the ductus arteriosus joins the aorta.

Coarctation reduces blood flow to the lower half of the body; therefore, the blood pressure is lower than normal in the legs and tends to be higher than normal in the arms. Coarctation is a serious but treatable cause of high blood pressure. A heart murmur is sometimes present. Without treatment, coarctation eventually strains and enlarges the heart, causing heart failure; it also causes high blood pressure. Coarctation makes the child susceptible to rupture of the aorta, bacterial endocarditis, and bleeding in the brain. Children with coarctation often have other heart defects, such as aortic valve stenosis or an atrial or ventricular septal defect.

For most infants, mild or moderate coarctation does not cause symptoms. Rarely, children with coarctation have headaches or nosebleeds because of high blood pressure in the arms, or leg pains during exercise because of insufficient blood and oxygen to the legs.

With a severe coarctation in infancy, blood can flow only to the lower portion of the aorta (at a point past its narrowing) through the open connection between the aorta and the pulmonary artery, the ductus arteriosus. Symptoms usually do not occur until the ductus closes, usually when the newborn is a few days to about 2 weeks old. After the closure, the blood supplied through the ductus disappears, sometimes causing sudden loss of almost the entire blood supply to the lower body. Sudden, catastrophic heart failure and low blood pressure can result.

Coarctation is usually suspected only when a doctor notices a heart murmur or differences in pulses or blood pressures between the arms and legs when performing a physical examination. X-rays, electrocardiography, and echocardiography are usually used to confirm the diagnosis.

Coarctation that does not cause severe symptoms should be surgically repaired in early childhood, usually when the child is about 3 to 5 years old. Infants with severe symptoms from coarctation require emergency treatment, including giving a prostaglandin such as alprostadil Some Trade Names CAVERJECT PROSTIN VR to reopen the ductus arteriosus, other drugs to strengthen the heart's pumping, and emergency surgery to widen the narrowing. Some infants who undergo emergency surgery need more surgery when they are older. Sometimes, instead of surgery, doctors use balloon angioplasty and stents to relieve coarctation.

Last full review/revision April 2006 by Gregory S. Liptak, MD, MPH

Source: The Merck Manual Home Edition