Congenital Heart Disease

content developed with: http://www.mayoclinic.org/

Congenital heart disease is not a single disease but refers to many different structural defects in the heart that can be present in an infant at birth. Congenital simply means present at birth, not necessarily inherited. Heart defects are abnormal changes in the structure of the heart or major vessels in and around the heart. Other terms for congenital heart disease are cyanotic heart disease, heart defects, or congenital cardiovascular malformations.

Heart defects are the most common birth defect; 8 of every 1,000 babies are born with some sort of structural defect in their heart. Congenital heart defects are the leading cause of death from birth defects during the first year of life. However, over the past 50 years, dramatic advances have been made in the treatment and correction of these defects resulting in a 25 percent decrease in deaths from congenital heart disease from 1992 to 2002. Today, there are about 1 million adults with congenital heart disease in the United States.

A common misconception for people with congenital heart disease is that once the defect is corrected, additional medical care is not needed. Even though a heart defect is repaired, the heart will be vulnerable to additional complications that can lead to heart failure. It is vital to the long-term survival of individuals born with a heart defect to see a cardiologist specializing in congenital heart defects on a regular basis for the rest of their lives.

This section has more on:

  • Need-to-know anatomy: the healthy heart
  • Need-to-know anatomy: blood flow through the healthy heart
  • Types of defects
  • Causes
  • Risk factors
  • Need-to-know anatomy: The healthy heart

    In general, the structure of the heart can be thought of as a two-story house with four rooms or chambers. The heart itself is constructed of muscle tissue known as the myocardium. Muscle fibers are the building blocks of the tissue. They not only provide the power for pumping but also transmit electrical signals throughout the heart.

    On the main floor are the two largest rooms—the left and right ventricles. The ventricles are the main pumping chambers of the heart. In a healthy heart, the left ventricle is the stronger pumping chamber where the internal pressures exceed those within the right ventricle. The wall separating the two ventricles is called the ventricular septum.

    The upper story has two smaller rooms—the left and right atria. The atria function primarily as receiving chambers for blood, but they also help out slightly with pumping. The wall between the two atria is called the atrial septum.

    The valves of the heart, constructed of strong, thin leaflets of tissue, function like one-way doors. Their primary role is to control the direction of blood flow; this keeps the heart working efficiently. The four valves in the heart are tricuspid, mitral, pulmonary, and aortic valves. The pulmonary and the aortic valves are the main exits from the heart. The pulmonary valve opens to the pulmonary artery, the passageway connecting the lungs with the right ventricle. The aortic valve opens to the aorta, which channels blood and nutrients to rest of the body. The mitral and tricuspid valves are the interior doors on the heart's left and right sides, respectively. The mitral valve is the located between the left atrium and the left ventricle. The tricuspid valve separates the right atrium from the right ventricle.

    The pulmonary and the aortic arteries are the main pathways for blood in and around the heart. The pulmonary artery is the pathway between the right ventricle and the lungs. The aorta channels blood to the body. The coronary arteries, which branch off the aorta, distribute blood to the heart itself. The pulmonary veins channel blood from the lungs to the left ventricle.

    Need-to-know anatomy: Blood flow through the healthy heart

    Although the heart is a muscle, the primary pumping action of the heart is more like a spring that contracts and relaxes. When the spring is relaxed, the ventricles simultaneously fill with blood. When the spring contracts, the ventricles eject a portion of the blood to either the lungs or the rest of the body. That exact portion is called the ejection fraction and in a healthy heart is greater than 60 percent. Like a spring, if it is continually overextended, the ventricle will ultimately lose the ability to contract.

    The right side of the heart is responsible for pumping blood to the lungs. In a healthy heart, oxygen-poor blood enters the heart at the right atrium on the top floor. When the right atrium fills with blood, the atrium contracts slightly and the blood is gently pumped through the open tricuspid valve down into the right ventricle. When the right ventricle is filled with blood, the tricuspid valve closes to prevent blood from leaking back into the right atrium. The heart then contracts strongly and pumps the blood out through the open pulmonary valve into the pulmonary artery. The pulmonary valve then closes to prevent blood leaking back into the right ventricle. The blood briefly leaves the heart at this point to pick up oxygen in the lungs.

    The oxygenated blood leaves the lungs and returns to the heart via the pulmonary veins, re-entering the heart at the left atrium, one of the upper chambers in the heart. The blood exits the left atrium through the mitral valve to flow into the left ventricle. The heart then contracts strongly, pumping the blood out through the aortic valve, the main exit door from the heart. The aortic valve keeps the oxygen-rich blood from leaking back into the left ventricle while maintaining flow into the aorta to deliver oxygen and nutrients to the rest of the body. The coronary arteries branch directly off the aorta and distribute the oxygenated blood to the heart itself. The left side of the heart is responsible for circulating blood to the entire body, powered by the left ventricle—normally the strongest pumping chamber in the heart where the pressures are greatest.

    Types of defects

    Any part of the cardiovascular system can be affected by congenital problems, and frequently more than one defect occurs in an individual. Some defects are mild enough to go unnoticed at birth; others cause major problems and even death shortly after birth. In general, heart defects are highly variable, so it is critical for individuals with them to find a cardiologist experienced in heart defects to monitor their health over the long term.

    The 24 most common defects can be grouped into five basic types:

    • Abnormal heart valves
    • Abnormal passages in or around the heart
    • Abnormal location of blood vessels
    • Defects in the heart tissue
    • Rhythm defects
    • Types of defects: Abnormal heart valves

      Heart valve defects are among the most common heart defects, with up to 2 percent of the population living with a bicuspid aortic valve. Most valve defects are identified at birth, but some may go unrecognized for 50 years. It can take decades before damage to the heart valves manifests as symptoms, because the heart is very good at adapting and compensating for defects. However, these adaptations can eventually be overwhelmed, leading to heart failure. Valve defects need to be corrected before irreversible damage to the heart occurs. The most common valve defects include:

      Valve stenosis: aortic or pulmonary valves. These very common defects are characterized by a narrowing of the aortic or pulmonary valve. Valve stenosis results in blood backing up behind the valve, which reduces the blood flow in the heart and body, and increases pressure within the heart.

      Bicuspid aortic valve. A bicuspid valve is malformed, constructed of two leaflets instead of three. With time, the leaflets tend to thicken and cause narrowing or stenosis. Sometimes the valve leaks blood back into the left ventricle (regurgitation). This increases the volume of blood for the heart to pump, which can make the left ventricle dilate and sometimes fail.

      Valve atresia: pulmonary or tricuspid valves - Valve atresia is a rare, complicated defect in which a solid sheet of tissue forms in place of the valve. It is often associated with ventricular septal defects and results in abnormal blood flow—the blood cannot follow the normal path to the lungs to be oxygenated.

      Valve regurgitation. Regurgitation of the valve means the valve does not close completely, allowing blood to flow backwards into the ventricle or atrium. Valve regurgitation decreases pumping efficiency, increasing the workload of the heart, and occurs more commonly in the aortic, mitral, or tricuspid valves.

      Ebstein's anomaly. This is a very rare defect in which the tricuspid valve is both misshapen and displaced. The defective tricuspid valve allows blood to flow backwards into the right atrium instead of to the lungs. It is frequently associated with atrial septal defects and abnormal heart rhythm disturbances.

      Types of defects: Abnormal passages in or around the heart

      These abnormalities are generally characterized by an extra pathway in the heart for blood flow, resulting from a hole in the heart or even an extra artery.

      A trial septal defect is a hole in the atrial septum that separates the two upper chambers of the heart and accounts for 25 percent of congential heart defects in adults. ASDs allow oxygenated blood to flow into the right atrium and back into the lungs, which increases the workload of the right side of the heart. The most common form of this defect, called a secundum ASD, is a hole in the central portion of the atrial septum. Atrial septal defects are three times as common in women as in men and can be difficult to diagnose. A young child may have no symptoms and the defect is tough to detect on physical exam alone; however, ASDs can be seen on chest X-ray or heard with careful auscultation of the heart and lungs during a routine checkup.

      Atrioventricular septal defect can be either complete or partial. Partial AVSD, also known as partial AV canal or primum ASD, is a hole in the lower part of the wall between the upper chambers of the heart atria (atrial septum) and is always associated with abnormal development of the mitral and tricuspid valves. Partial AVSD increase the workload for the right side of the heart and are often associated with mitral valve regurgitation. Complete AVSD, also known as complete atrioventricular canal, common AV canal, and endocardial cushion defect, accounts for 4 to 10 percent of congenital heart defects. People with complete AVSD have holes in both the atrial and ventricular septums as well as abnormal tricuspid and mitral valves. AVSD cause oxygen-rich and oxygen-poor blood to mix within the heart. This increases blood flow through the lungs, overworking the heart.

      Patent ductus arteriosus. The ductus arteriosus is an artery that is normally present in the developing fetus that allows blood to bypass the fetal lungs until the lungs become functional at birth. In some people this artery fails to close at birth, resulting in an extra artery, the patent ductus arteriosus, where patent means open. In a newborn, this connection creates an extra circulation path outside the heart allowing oxygenated blood in the aorta to circulate into the pulmonary artery, resulting in excess blood flow to the lungs. This extra circulatory pathway overworks the heart and can cause high pressure in the lungs (pulmonary hypertension) or heart failure.

      Ventricular septal defect is a hole in the wall (ventricular septum) between the pumping chambers of the heart and accounts for 15 percent of all congenital heart disease. VSDs allow oxygen-rich and oxygen-poor blood to mix in the ventricles, increasing the blood flow to the lungs and overworking the heart.

      Types of defects: Abnormal location of blood vessels

      The two great highways in the heart are the pulmonary artery, which carries blood to the lungs to be oxygenated, and the aorta, which carries oxygenated blood to the body. Defects in the locations of these pathways can dramatically affect the circulation of blood in the body, with the result that tissues throughout the body don't get enough oxygen and nutrients to function properly.

      Transposition of the great arteries. This condition, in which the locations of the pulmonary and aortic arteries are reversed, results in two—instead of one—circulatory patterns in the body accounts for approximately 10 percent of congenital heart defects. When the aorta is attached to the right ventricle instead of the left, nonoxygenated blood circulates through the body in a more or less closed loop, never flowing through the lungs to be oxygenated. Since the pulmonary artery is connected to the left ventricle instead of the right, oxygen-rich blood is pumped back to the lungs instead of to the body. When the great arteries are transposed, the tissues of the body do not get enough oxygen.

      Congenitally corrected transposition of the great arteries. With this defect, not only are the locations of the arteries reversed (transposed) but so are the connections between the atria and ventricles. This second abnormal connection is, in a sense, "corrective" since the blood still flows in the appropriate direction but is being pumped by the "wrong" ventricle. Thus the left ventricle pumps to the lungs and the right ventricle pumps blood to the body via the aorta. This structural change results in the weaker of the ventricles, the right, carrying the greater workload of the heart and can potentially lead to heart failure.

      Tetralogy of Fallot. This common defect, accounting for 9 to14 percent of congenital heart defects, is really four defects in combination. It features a ventricular septal defect, an obstruction to blood flow beneath the pulmonary valve, an aorta that is shifted to the right, and a thickened right ventricular wall. The net result is decreased blood flow to the lungs and the circulation of nonoxygenated blood to the body.

      Truncus arteriosus. In this rare defect, the pulmonary and aortic arteries originate out of a single large artery or trunk. With a single trunk, oxygen-rich and oxygen-poor blood are mixed during circulation, resulting in some oxygen-rich blood being redirected to the lungs to be reoxygenated and some oxygen-poor blood being recirculated in the body.

      Coarctation of the aorta. Coarctation is a relatively common defect accounting for 8 to 11 percent of congenital heart defects in adults. It occurs more frequently in men and is characterized by localized narrowing or constriction in the aorta. Coarctation obstructs blood flow from the heart to the body and may increase the risk of stroke and premature coronary artery disease.

      Anomalous pulmonary veins. In this very rare defect, one or more of the pulmonary veins responsible for carrying oxygen-rich blood from the lungs to the heart is attached to the right side of the heart instead of the left. As a result, the right side of the heart carries an increased volume of blood and may enlarge and fail.

      Types of defects: Defects in the heart tissue

      These are defects in the heart tissue itself as opposed to the valve or arteries.

      Hypoplastic left heart syndrome. The left side of the heart is underdeveloped in people with this condition. Frequently, the pumping capability of the left ventricle is severely limited, the aortic and mitral valves are closed (atresia), and the aorta itself is poorly developed. If untreated, this defect is normally fatal within the first several days after birth.

      Single ventricle. Single ventricle refers to a group of heart defects in which only one ventricle-the right or the left, is functionally present. It is one of the most complicated defects to treat and manage. These defects often involve all the structures on the affected side, greatly diminishing heart functioning.

      Eisenmenger's syndrome is characterized by an opening in the heart, coupled with pulmonary hypertension. The hole is usually between the ventricles (ventricular septal defect) and allows blood to flow from the left ventricle, where the pressures are high, into the right ventricle, which typically has lower pressure. This forces more blood than normal into the lungs, which raises the pressure in the arteries of the lungs, a condition known as pulmonary hypertension. Over time, pulmonary hypertension will damage the blood vessels in the lungs, making them resistant to blood flow, which in turn increases pressures in the right ventricle. The pressures in the right ventricle will continue to rise until they exceed the pressure in the left ventricle, at which time blood will be forced back through the VSD into the left ventricle to alleviate the pressure buildup. When this happens, oxygen-poor blood in the right ventricle mixes with the oxygenated blood in the left ventricle. This mixture of oxygenated and nonoxygenated blood is then circulated throughout the body, causing a dusky blue color in the skin called "cyanosis."

      Hypertrophic cardiomyopathy is characterized by an abnormal thickening of the heart muscle and changes in the structure of the muscle fibers of the heart. These defects interfere with the heart's pumping ability by reducing blood flow in and out of the heart chambers and can lead to sudden death in 1 percent of the people affected by this disease. More information on hypertrophic cardiomyopathy can be found in the hypertrophic cardiomyopathy module.

      Types of defects: Heart rhythm defects

      Congenital heart rhythm defects, which involve the electrical or conduction system of the heart, are rare. The heart's electrical conduction system functions like microscopic wiring, stimulating the heart muscle to contract in a specific sequence so that the blood circulates through the heart and lungs efficiently and oxygen and nutrients are delivered to the rest of the body.

      One example of a congenital heart rhythm defect is long QT syndrome, in which an individual is vulnerable to fast, chaotic heartbeats that may lead to fainting and even cardiac arrest.

      Causes

      The exact cause of any one congenital heart defect is rarely identified. However, most experts believe that abnormal genes coupled with environmental factors experienced during early pregnancy lead to congenital heart defects.

      The heart is one of the first organs to develop in the fetus. At approximately three weeks of gestation, a tiny tube is formed and the fetal heart begins to beat. During the next few days, the tube begins to bend and fold in on itself, forming a loop that roughly takes the shape of the heart. By the 18th week of pregnancy, this tiny tube has molded into all of the basic structures of the heart. It's possible for physicians to detect some heart defects by the 18th week of pregnancy.

      Genes contain the sets of instructions that guide the process of development. If these instructions are jumbled, the heart will fail to develop normally. For example, if the instructions for developing the aortic valve are incorrect, the valve may be absent altogether, as in aortic valve atresia, or misshapen, as in aortic valve stenosis.

      Scientists are on the verge of discovering the genes that are associated with numerous heart defects. Currently, more than 100 mutations in several genes have been linked with congenital heart defects. Most of these genetic links are associated with hypertrophic cardiomyopathy, but other genetic mutations have been linked to septal defects and defects in the outflow path from the heart.

      Risk factors

      Anyone can have a child with a congenital heart defect. The risk of any a mother giving birth to a child with congenital heart defects is about 1 percent.

      If you have a relative with a heart defect or already have a child with a defect, the chance of problems in your future children does rise slightly. However, unless a specific chromosomal problem is identified, or a clear pattern of hereditary heart disease is seen in a family tree, most experts believe the risk that a developing embryo will acquire a heart defect is about 2 to 5 percent. In other words, there is a 95 to 98 percent chance of a baby being born without a heart defect.

      Approximately 10 percent of congenital heart defects are associated with a chromosomal abnormality. One third of the children with Down syndrome also have a congenital heart defect, as do one quarter of the girls with Turner syndrome. Children with Down and Turner syndromes should be evaluated for congenital heart defects.

      The following factors are associated with an increased risk of congenital heart disease:

      • Viral infections. Women who contract the virus rubella, commonly known as German measles, during the first few weeks of pregnancy have an increased risk of having a baby with a heart defect. Women who contract upper respiratory tract infections in the early stages of pregnancy-even minor ones-may also be at increased risk.
        • Certain medications and street drugs. Women who take medicines such as the acne medication isotretinoin (brand name Accutane), lithium (commonly prescribed for bipolar disorder), and possibly some antiseizure medications put the developing fetus at increased risk for congenital heart disease. Drinking alcohol and using cocaine while pregnant also puts a fetus at increased risk.
          • X-rays and strong chemicals such as solvents. Repeated exposure to these by the mother may increase the risk.
            • Diabetes or phenylketonuria. Women with diabetes are at increased risk of having a baby with a congenital heart defect, as are women who develop phenylketonuria (PKU) during pregnancy. In both these cases, these risks can be minimized through proper management and diet.
            • Last reviewed on 2/11/2009

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