congenital heart disease(redirected from left shunt)
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Congenital heart disease
Congenital heart disease, also called congenital heart defect, includes a variety of malformations of the heart and/or its major blood vessels that are present at birth.
Congenital heart disease occurs when the heart or blood vessels entering or leaving the heart do not develop normally before birth. Some infants are born with mild types of congenital heart disease that do not become apparent until later in life, but others need surgery as newborns or infants in order to survive.
Congenital heart disease is the most common birth defect. About 35,000 infants are born each year with some form of congenital heart disease. About half of these cases require medical treatment; the rest either correct (resolve) spontaneously shortly after birth or are so mild as to need no treatment or to go undetected. More than 1.4 million people with congenital heart defects were living in the United States in 2007.
Anatomy of the heart
The heart has four compartments or chambers, a left and right atrium above a left and right ventricle. These chambers keep blood carrying oxygen (oxygenated blood) from mixing with blood that has already given up its oxygen to cells (deoxygenated blood). Blood moves through the heart in a specific pattern. Deoxygenated blood returning from the body enters the right atrium. It moves through a valve into the right ventricle. When the right ventricle contracts, blood is pumped through another valve and is carried to the lungs where it picks up oxygen. The newly oxygenated blood returns to heart and enters the left atrium. It flows through a valve into the left ventricle, and is then pumped through another valve to the aorta, a large artery. From the aorta, oxygenated blood is distributed to the rest of the body. Congenital heart disease causes a disruption or inefficiency in this pattern.
There are many types of congenital heart defects, but they fall into four major categories:
- defects that obstruct the flow of blood to the heart, lungs, or the nearby blood vessels. This can be caused by narrowed or malformed blood vessels or heart valves.
- defects that allow oxygenated and deoxygenated blood to mix. This can be caused by holes in the partitions (septa) between chambers or leaky valves that separate the chambers.
- arrhythmias, which are defects in the timing of contractions of the various chambers so that the chambers do not fill and empty completely; heartbeat may be too fast, too slow, or uncoordinated.
- major structural defects such as missing or underdeveloped heart chambers or incorrectly located blood vessels.
When heart valves, arteries, or veins are narrowed, they partly or completely block the flow of blood. The most common obstruction defects are pulmonary valve stenosis, aortic valve stenosis, and coarctation of the aorta. Bicuspid aortic valve and subaortic stenosis are less common.
Stenosis is a narrowing of the valves or arteries. In pulmonary stenosis, the pulmonary valve does not open properly, forcing the right ventricle to work harder. In aortic stenosis, the improperly formed aortic valve is narrowed. As the left ventricle works harder to pump blood through the body, it becomes enlarged. In coarctation of the aorta, the aorta is constricted, reducing the flow of blood to the lower part of the body and increasing blood pressure in the upper body.
A bicuspid aortic valve has only two flaps instead of three, which can lead to stenosis in adulthood. Subaortic stenosis is a narrowing of the left ventricle below the aortic valve that limits the flow of blood from the left ventricle.
Heart defects that cause a decreased, inadequate amount of oxygen in blood pumped to the body are called cyanotic defects. When a baby is born with a hole in the septum (the wall separating the right and left sides of the heart), blood can leak from one chamber to another, allowing oxygenated and deoxygenated blood to mix. This causes less oxygen to be delivered to the body. Major leakage can lead to enlargement of the heart and failing circulation. The most common types of septal defects are atrial septal defect, an opening between the two upper heart chambers, and ventricular septal defect, an opening between the two lower heart chambers. Ventricular septal defect accounts for about 15% of all cases of congenital heart disease in the United States.
Patent ductus arteriosus refers to the opening of a temporary blood vessel (ductus) that carries blood from the heart to the aorta before birth, allowing blood to bypass the lungs, which are not yet functional. The ductus should close spontaneously in the first few hours or days after birth. When it does not close in the newborn, some of the blood that should flow through the aorta returns to the lungs. Patent ductus arteriosus is common in premature babies, but rare in full-term babies. It also has been associated with mothers who had German measles (rubella) while pregnant.
Ebstein's anomaly is a rare congenital syndrome that causes malformed tricuspid valve leaflets, which allow blood to leak between the right ventricle and the right atrium. It also may cause a hole in the wall between the left and right atrium. Treatment often involves repairing the tricuspid valve.
Other cyanotic defects, including truncus arteriosus, total anomalous pulmonary venous return, and tetralogy of Fallot, result in a blue discoloration of the skin due to low oxygen levels. About 10% of cases of congenital heart disease in the United States are tetralogy of Fallot, which includes four defects. The major defects are a large hole between the ventricles, which allows oxygen-poor blood to mix with oxygen-rich blood, and narrowing at or beneath the pulmonary valve. The other defects are an overly muscular right ventricle and an aorta that lies over the ventricular hole.
Major structural defects
In transposition (reversal of position) of the great arteries, the pulmonary artery and the aorta are reversed, causing oxygenated blood to re-circulate to the lungs while deoxygenated blood goes to the rest of the body. In tricuspid atresia, the baby lacks a triscupid valve and blood cannot flow properly from the right atrium to the right ventricle.
Hypoplastic left heart syndrome, a condition in which the left side of the heart is underdeveloped, is rare, but it is the most serious type of congenital heart disease. With this condition, blood reaches the aorta only from the ductus, which then closes normally within a few days of birth. In hypoplastic left heart syndrome, the baby seems normal at birth, but as the ductus closes, blood cannot reach the aorta and circulation fails.
Infants born with DiGeorge sequence can have heart defects such as a malformed aortic arch and tetralogy of Fallot. Researchers believe DiGeorge sequence most often is caused by mutations in genes in the region 22q11.
Brugada syndrome is another rare congenital heart defect that appears in adulthood and may cause sudden death if untreated. Symptoms, which include rapid, uneven heart beat, often appear at night. Scientists believe that Brugada syndrome is caused by mutations in the gene SCN5A, which involves cardiac sodium channels.
Marfan syndrome is a connective tissue disorder that causes tears in the aorta. Since the disease also causes excessive bone growth, most Marfan syndrome patients are over six feet tall. In athletes, and others, it can lead to sudden death. Researchers believe the defect responsible for Marfan's syndrome is found in gene FBN1, on chromosome 15.
Causes and symptoms
In most cases, the causes of congenital heart disease are unknown. Genetic, environmental, and lifestyle factors all can be involved. The likelihood of having a child with congenital heart disease increases if a parent or other close relative has congenital heart disease or if there is a family history of early sudden cardiac death. Congenital heart disease is common in children with other genetic disorders that affect many organ systems, such Down syndrome. In addition, as of 2008, researchers had identified about ten genetic changes (mutations) that caused some type of congenital heart disease, but no widespread symptoms.
During pregnancy, viral infections such as German measles can result in congenital heart disease in the newborn. Women with diabetes and phenylketonuria (PKU, an inherited liver disorder) also are at higher risk of having children with congenital heart defects. Some cases of congenital heart disease result from the mother's excessive use of alcohol or taking illegal street drugs, such as cocaine or methamphetamines, during pregnancy. The mother's use of certain anticonvulsant (anti-seizure) drugs or dermatologic drugs (e.g., isotretinon [Accutane and other brand names], thalidomide) during pregnancy also can cause congenital heart disease.
Symptoms of congenital heart disease in general include shortness of breath, difficulty feeding in infancy, excessive sweating, cyanosis (bluish discoloration of the skin), heart murmur, respiratory infections that recur excessively, stunted growth, and limbs and muscles that are underdeveloped.
Symptoms of specific types of congenital heart disease are as follows:
- Patent ductus arteriosus: quick tiring, slow growth, susceptibility to pneumonia, rapid breathing. If the ductus is small, there are no symptoms.
- Hypoplastic left heart syndrome: ashen color, rapid and difficult breathing, inability to eat.
- Obstruction defects: cyanosis (skin that is discolored blue), chest pain, tiring easily, dizziness or fainting, congestive heart failure, and high blood pressure.
- Septal defects: difficulty breathing, stunted growth. Sometimes there are no symptoms.
- Cyanotic defects: cyanosis, sudden rapid breathing or unconsciousness, and shortness of breath and fainting during exercise.
Echocardiography and cardiac magnetic resonance imaging (MRI) commonly are used to confirm congenital heart disease when it is suggested by the symptoms and physical examination. These are noninvasive (nothing enters the body) tests. An echocardiograph displays an image of the heart that is formed by sound waves. It may detect valve and other heart problems. Fetal echocardiography is used to help diagnose congenital heart disease in utero, usually after 20 weeks of pregnancy. Between 10 and 14 weeks of pregnancy, physicians also may use an ultrasound to look for a thickness at the nuchal translucency, a pocket of fluid in back of the embryo's neck, which may indicate a cardiac defect. Cardiac MRI, a scanning method that uses magnetic fields and radio waves, can help physicians evaluate congenital heart disease, but is not always necessary. Physicians also may use a chest x ray to look at the size and location of the heart and lungs, or an electrocardiograph (ECG), which measures electrical impulses to create a graph of the heartbeat. After birth pulse oximetry is a noninvasive way to measure the amount of oxygen in the blood (a sensor is clipped on a finger or toe). Cardiac catheterization, an invasive test done under anesthesia, allows a dye to be inserted into the heart so that blood circulation through the heart can be seen on an x ray. Cardiac catheterization also can measure pressure in the heart chambers to determine if there is blood mixing or leakage between heart chambers.
Congenital heart disease is treated with drugs and/or surgery. Drugs used include diuretics, which increase the excretion water and salts, and digoxin, which strengthens the contraction of the heart, slows the heartbeat, and removes fluid from tissues.
Surgical procedures seek to repair the defect as much as possible and restore circulation to as close to normal as possible. Sometimes, multiple surgical procedures are necessary. Surgical procedures include arterial switch, balloon atrial septostomy, balloon valvuloplasty, Damus-Kaye-Stansel procedure, Fontan procedure, pulmonary artery banding, Ross procedure, shunt procedure, and venous switch or intra-atrial baffle.
Arterial switch, to correct transposition of the great arteries, involves connecting the aorta to the left ventricle and connecting the pulmonary artery to the right ventricle. Balloon atrial septostomy, also done to correct transposition of the great arteries, enlarges the atrial opening during heart catheterization. Balloon valvuloplasty uses a balloon-tipped catheter to open a narrowed heart valve, improving the flow of blood in pulmonary stenosis. It is sometimes used in aortic stenosis. Transposition of the great arteries also can be corrected by the Damus-Kaye-Stansel procedure, in which the pulmonary artery is cut in two and connected to the ascending aorta and the farthest section of the right ventricle.
For tricuspid atresia and pulmonary atresia, the Fontan procedure connects the right atrium to the pulmonary artery directly or with a conduit, and the atrial defect is closed. Pulmonary artery banding, narrowing the pulmonary artery with a band to reduce blood flow and pressure in the lungs, is used for ventricular septal defect, atrioventricular canal defect, and tricuspid atresia. Later, the band can be removed and the defect corrected with open-heart surgery.
To correct aortic stenosis, the Ross procedure grafts the pulmonary artery to the aorta. For tetralogy of Fallot, tricuspid atresia, or pulmonary atresia, the shunt procedure creates a passage between blood vessels, sending blood into parts of the body that need it. For transposition of the great arteries, venous switch creates a tunnel inside the atria to re-direct oxygen-rich blood to the right ventricle and aorta and venous blood to the left ventricle and pulmonary artery.
When surgery is not a viable option to correct the problem, some patients undergo a heart transplant. Children with congenital heart disease require lifelong monitoring, even after successful surgery. The American Heart Association recommends regular dental check-ups and preventive use of antibiotics to protect patients from heart infection (endocarditis). However, a 2003 study reported that preventive antibiotics are underused in people with congenital heart disease. Many patients did not understand the risk of endocarditis. Since children with congenital heart disease often have slower growth, good nutrition is important. Physicians also may limit their athletic activity.
The outlook for children with congenital heart disease has improved markedly in the past two decades. Many types of congenital heart disease that would have been fatal now can be treated successfully. Because many children with these defects survive into adulthood, they will require continued medical observation as they mature. Research on diagnosing heart defects when the fetus is in the womb may lead to future treatment to correct some defects before birth. Promising new prevention methods and treatments include genetic screening and the cultivation of cardiac tissue in the laboratory that might be useful in repairing some congenital heart defects. As scientists continue to advance the study of genetics, they also will better understand genetic causes of many congenital heart diseases.
- The main artery located above the heart that pumps oxygenated blood out into the body. Many congenital heart defects affect the aorta.
- Atrium (plural Atria)
- The right or left upper chamber of the heart.
- Cardiac catheterization
- A diagnostic procedure (using a catheter inserted through a vein and threaded through the circulatory system to the heart) which does a comprehensive examination of how the heart and its blood vessels function.
- Refers to a disorder that is present at birth.
- Marked by bluish discoloration of the skin due to a lack of oxygen in the blood. It is one of the types of congenital heart disease.
- The blood vessel that joins the pulmonary artery and the aorta. When the ductus does not close at birth, it causes a type of congenital heart disease called patent ductus arteriosus.
- A non-invasive imaging procedure used to create a picture of the heart's movement, valves, and chambers.
- Electrocardiograph (ECG, EKG)
- A test used to measure electrical impulses coming from the heart in order to gain information about its structure or function.
- Infection of the heart endocardium tissue, the inner most tissue and structures of the heart.
- Incomplete or underdevelopment of a tissue or organ. Hypoplastic left heart syndrome is the most serious type of congenital heart disease.
- Marfan syndrome
- An inherited condition that affects connective tissue throughout the body including weakening the connective tissue found in arteries.
- Neuchal translucency
- A pocket of fluid at the back of an embryo's neck visible via ultrasound that, when thickened, may indicate the infant will be born with a congenital heart defect.
- Relating to the septum, the thin muscle wall dividing the right and left sides of the heart. Holes in the septum are called septal defects.
- Stenosis (plural, stenoses)
- The narrowing or constriction of an opening or passageway in the body.
- A lower pumping chambers of the heart. There are two ventricles, right and left. The right ventricle pumps oxygen-poor blood to the lungs to be re-oxygenated. The left ventricle pumps oxygen-rich blood to the body.
For Your Information
- Kramer, Gerri Freid and Shari Maurer. The Parent's Guide to Children's Congenital Heart Defects: What They Are, How to Treat Them, How to Cope With Them. New York: Three Rivers Press, 2001.
- Neill, Catherine. The Heart of a Child: What Families Need to Know about Heart Disorders in Children, Baltimore: Johns Hopkins University Press, 2001.
- Gerber, Max S. My Heart vs. the Real World: Children with Heart Disease, In Photographs & Interviews. Cold Spring Harbor, N.Y. : Cold Spring Harbor Laboratory Press, c2008.
- "Congenital Heart Defects." MedlinePlus. February 11, 2009 [cited February 12, 2009]. http://www.nlm.nih.gov/medlineplus/congenitalheartdefects.html.
- "Fact Sheet: Congenital Heart Defects." March of Dimes. May 2008 [cited February 12, 2009]. http://www.marchofdimes.com/professionals/14332_1212.asp.
- National Heart, Lung, and Blood Institute. "Congenital Heart Defects." Medicinenet.com. May 12, 2008 [cited February 12, 2009]. http://www.medicinenet.com/congenital_heart_disease/article.htm.
- American Heart Association. 7272 Greenville Avenue, Dallas, TX 75231. Telephone: (800) 242-8721. http://www.americanheart.org .
- Congenital Heart Information Network. 600 North 3rd Street, 1st floor, Philadelphia, PA 19123-2902. Telephone: (215) 627-4934 Fax: (215)627-4036 http://tchin.org.
- March of Dimes Birth Defects Foundation. 1275 Mamaroneck Ave., White Plains, NY 10605. Telephone: (914) 997-4488. http://www.modimes.org..
- National Heart Lung and Blood Institute Health Information Center. P.O. Box 30105, Bethesda, MD 20824-0105. (301) 592 8573. http://www.nhlbi.nih.gov.
Congenital heart defects
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
congenital heart diseaseA congenital malformation–eg, coarctation of aorta, VSD, ASD, tetraology of Fallot–of the heart or great blood vessels, which may or may not have clinical consequences. See Baby Faye heart, Shunt.
Congenital heart disease
Right→left shunt Cyanotic shunt Tetralogy of Fallot, transposition of the great vessels, trucus arteriosus, tricuspid valve atresia
Left→right shunt Acyanotic shunt Patent ductus arteriosus, atrial septal defect, ventricular septal defect, aortic stenosis, pulmonary stenosis, aortic coarctation (NEJM 2000; 342:256rv)
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.
congenital heart diseaseA range of heart disorders, of varying degrees of severity, present at birth. Congenital heart disease affects about one live baby in 120 and is caused by factors operating early in pregnancy. These include virus infections, especially RUBELLA, drugs, DIABETES and SYSTEMIC LUPUS ERYTHEMATOSUS in the mother. Congenital heart disease is a feature of DOWN'S SYNDROME and other chromosomal defects, including TRISOMY 13 and TRISOMY 18. The diseases include ‘hole in the heart’ (SEPTAL DEFECTS), PATENT DUCTUS ARTERIOSUS, pulmonary valve narrowing (stenosis), AORTIC STENOSIS and FALLOT'S TETRALOGY.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005