Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Overview of Heart Defects

By

Lee B. Beerman

, MD, Children's Hospital of Pittsburgh of the University of Pittsburgh School of Medicine

Reviewed/Revised Apr 2023
VIEW PROFESSIONAL VERSION
Topic Resources

About one in 100 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.

  • Symptoms of heart birth defects vary with age. Infants may have labored or rapid breathing, poor feeding, sweating or increased breathing rate while feeding, bluish discoloration (cyanosis) of the lips or skin, unusual irritability, or failure to gain weight. Toddlers may tire easily during activity or have a rapid heart beat. Older children and adolescents may have decreased activity tolerance, chest pain during activity, awareness of heartbeats (palpitations), dizziness, or fainting.

  • During examination, a doctor may notice abnormal skin color, abnormal pulsations of the left side of the chest, a heart murmur or other abnormal sounds, a rapid heart beat, rapid or labored breathing, weak pulses, and/or a large liver.

  • Echocardiography (ultrasonography of the heart) helps identify almost all heart defects.

  • Treatment includes open-heart surgery for severe defects, use of a catheter with a balloon at its tip to open or widen valves or blood vessels, use of a device placed by catheter to close certain holes or extra blood vessels, or medications.

The most common birth defect of the heart is a bicuspid aortic valve Bicuspid Aortic Valve A bicuspid aortic valve is an aortic valve that has two cusps (leaflets) instead of the normal three. (See also Overview of Heart Defects.) The aortic valve is the valve that opens with each... read more . The aortic valve is the valve that opens with each heartbeat to allow blood to flow from the heart to the body. A normal aortic valve has three cusps, or leaflets. When the valve is bicuspid, it has only two cusps instead of three. Bicuspid aortic valve usually does not cause problems in infancy or childhood so it may not be diagnosed until people become adults. The most common heart defects that are diagnosed in infancy and childhood are atrial and ventricular septal defects 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. Holes can be present in the walls of the heart between the upper heart... read more Atrial and Ventricular Septal Defects (holes between the chambers of the heart).

Did You Know...

  • About one in 100 babies is born with a heart defect.

Anatomy of the Heart

The heart is divided into two sides (right and left), and each side is divided into two chambers (an atrium and a ventricle). The atria and ventricles on both sides are separated from each other by valves.

On the right side of the heart

  • Blood enters from the vena cava (the largest vein in the body) and flows into the right atrium

  • Then flows through the tricuspid valve into the right ventricle

  • Then flows out of the heart through the pulmonary valve and into the pulmonary artery

  • The pulmonary artery delivers blood to the lungs (where the blood picks up oxygen and gets rid of carbon dioxide)

On the left side of the heart

  • Oxygen-rich blood enters from the pulmonary vein and flows into the left atrium

  • Then flows through the mitral valve into the left ventricle

  • Then flows out of the heart through the aortic valve and into the aorta (the largest artery in the body)

  • Blood circulates through the body, first through arteries, then through veins, and then through the vena cava (and back to the heart)

(See also and .)

Normal Fetal Circulation

Blood flow is different in the fetus than in children and adults.

In children and adults, all blood returning to the heart from the body (blue blood from the veins, which is low in oxygen) 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) of the lungs and also releases carbon dioxide (see Exchanging Oxygen and Carbon Dioxide Exchanging Oxygen and Carbon Dioxide The primary function of the respiratory system is to take in oxygen and eliminate carbon dioxide. Inhaled oxygen enters the lungs and reaches the alveoli. The layers of cells lining the alveoli... read more ). This blood, which is rich in oxygen and appears red, returns from the lungs to the left atrium and left ventricle, and from there it is pumped out of the heart to the body through a large artery called the aorta and then through smaller arteries.

In the fetus, the path by which blood circulates through the heart and lungs is different. Because the fetus is inside the uterus, it is not exposed to air, and its lungs are collapsed and filled with amniotic fluid (the fluid inside the uterus during pregnancy). Because the fetus does not breathe air while in the uterus, the fetus' blood gets oxygen through the placenta. The mother's oxygen-rich blood flows through the blood vessels of the uterus. The mother's blood does not flow directly to the fetus. Only the oxygen in the mother's blood transfers to the fetal blood in the placenta, which then passes to the fetus through the umbilical blood vessels (in the umbilical cord).

Before birth, much of the blood from the veins (venous blood) coming to the right side of the heart bypasses the nonfunctioning lungs and travels through two short-cuts (shunts) to get to the fetus' body. These short-cuts are

  • The foramen ovale, a hole between the two upper chambers of the heart, the right atrium and the left atrium

  • The ductus arteriosus, a blood vessel connecting the two great arteries leaving the heart, the pulmonary artery and the aorta

Prenatal Heart Circulation
VIDEO

In the fetus, venous blood arriving at the heart has received oxygen from the placenta. This oxygenated blood can be delivered to the body through the foramen ovale and the ductus arteriosus, largely bypassing the nonfunctioning lungs. This circulation pattern changes immediately after birth. During passage through the birth canal, fluid is squeezed out of the newborn's lungs. With the newborn's first breath, the lungs fill with air, which brings in oxygen. When the umbilical cord is cut, the placenta (and therefore the mother's circulation) is no longer connected to the newborn's circulation, and all the newborn's oxygen comes through the lungs. Thus, the foramen ovale and ductus arteriosus are no longer needed, and they usually close within the first days to weeks of life, making the newborn's circulation the same as that of an adult. Sometimes, the foramen ovale does not close (called patent foramen ovale), but a patent foramen ovale does not usually cause any health problems.

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. The fetus is not exposed to air. It is inside the uterus, and its lungs are collapsed and filled with amniotic fluid. Because the fetus does not breathe air, the fetus' blood gets oxygen that passes from the mother's blood vessels to the placenta. The oxygen-rich fetal blood in the placenta passes through the umbilical blood vessels (in the umbilical cord) and enters the fetal heart. Only a small amount of blood goes through the lungs. The rest of the blood bypasses the lungs by flowing through two short-cuts (shunts):

  • The foramen ovale, a hole between the right and left atria

  • The ductus arteriosus, a blood vessel that connects the pulmonary artery and the aorta

Normally, these two short-cuts close soon after birth.

Normal Circulation in a Fetus

Types of Heart Defects

The ways that heart defects cause changes in the normal blood flow to the lungs and body are

  • Shunting the flow of blood (blood flows through openings that are not part of the normal circulation)

  • Re-routing the flow of blood (blood flows through vessels that are arranged differently from the normal circulation)

  • Blocking the flow of blood, as occurs when a heart valve or blood vessel is defective

Shunting of blood flow

Shunting is usually classified as

  • Right-to-left

  • Left-to-right

Right-to-left shunting involves mixing of the oxygen-poor blood from the right side of the heart with the oxygen-rich blood in the left side of the heart that is pumped to the body tissues. The more oxygen-poor blood (which is blue) that flows to the body, the bluer the body appears, particularly the lips, tongue, skin, and nail beds. 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. Many different types of birth defects of the heart can cause right-to-left shunting and thus cyanosis, but one of the most common is tetralogy of Fallot Tetralogy of Fallot In tetralogy of Fallot, four specific heart defects occur together. This condition includes four heart defects that can lead to oxygen-poor blood going directly to the body. Symptoms include... read more .

Left-to-right shunting involves oxygen-rich blood, which is pumped under high pressures from the left side of the heart, mixing with oxygen-poor blood being pumped from the right side of the heart through the pulmonary artery to the lungs. Left-to-right shunting makes the circulation inefficient and increases the amount of blood flowing to the lungs, which sometimes also causes high pressure in the pulmonary artery. Over time, high flow and high pressure can damage the blood vessels of the lungs and overwork both the left and right sides of the heart, causing the heart muscle to become weak and not function (heart failure—see figure Heart Failure: Pumping and Filling Problems Heart Failure: Pumping and Filling Problems Heart Failure: Pumping and Filling Problems ). Examples of disorders in which left-to-right shunting occurs are ventricular septal defects 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. Holes can be present in the walls of the heart between the upper heart... read more Atrial and Ventricular Septal Defects , atrial septal defects 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. Holes can be present in the walls of the heart between the upper heart... read more Atrial and Ventricular Septal Defects , patent ductus arteriosis Patent Ductus Arteriosus In patent ductus arteriosus (PDA), the blood vessel connecting the pulmonary artery and the aorta (ductus arteriosus) fails to close as it usually does shortly after birth. Patent ductus arteriosus... read more Patent Ductus Arteriosus , and atrioventricular septal defects Atrioventricular Septal Defects Atrioventricular (AV) septal defect is a combination of heart defects. These include a hole in the wall that separates the upper chambers of the heart ( atrial septal defect), a single valve... read more .

Re-routing of blood flow

In transposition of the great arteries 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. The aorta and pulmonary artery are reversed, which causes oxygen-poor... read more Transposition of the Great Arteries , the normal connections of the aorta and the pulmonary artery to the heart are reversed. The aorta, which supplies the body, connects to the right ventricle instead of the left ventricle, and the pulmonary artery, which supplies the lungs, connects to the left ventricle instead of the right ventricle. As a result, oxygen-poor blood is circulated to the body, and oxygen-rich blood is circulated between the lungs and the heart and not the rest of the body. The body does not get enough oxygen, and severe cyanosis occurs within minutes of birth.

Blocked blood flow

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

Blockage of blood flow can lead to heart failure. Heart failure does not mean that the heart has stopped beating and is not the same as a heart attack. Heart failure means that the heart is unable to pump blood normally. As a result, blood from the left side of the heart may back up into the lungs and blood from the right side may back up into the body causing enlargement of the liver or swelling of the legs. Heart failure can also develop when the heart pumps too weakly (for example, when a baby is born with a weak heart muscle).

Causes of Heart Defects

Both environmental and genetic factors contribute to the development of birth defects of the heart.

Genetic factors that are strongly associated with birth defects of the heart include certain chromosome abnormalities, particularly Down syndrome Down Syndrome (Trisomy 21) Down syndrome is a chromosome disorder caused by an extra chromosome 21 that results in intellectual disability and physical abnormalities. Down syndrome is caused by an extra chromosome 21... read more Down Syndrome (Trisomy 21) , trisomy 13 Trisomy 13 Trisomy 13 is a chromosomal disorder caused by an extra chromosome 13 that results in severe intellectual disability and physical abnormalities. Trisomy 13 is caused by an extra chromosome 13... read more , trisomy 18 Trisomy 18 Trisomy 18 is a chromosomal disorder caused by an extra chromosome 18 that results in intellectual disability and physical abnormalities. Trisomy 18 caused by an extra chromosome 18. Infants... read more Trisomy 18 , and Turner syndrome Turner Syndrome Turner syndrome is a sex chromosome abnormality in which girls are born with one of their two X chromosomes partially or completely missing. Turner syndrome is caused by the deletion of part... read more Turner Syndrome . Other genetic disorders, such as DiGeorge syndrome DiGeorge Syndrome DiGeorge syndrome is a congenital immunodeficiency disorder in which the thymus gland is absent or underdeveloped at birth, causing problems with T cells, a type of white blood cell that helps... read more , Marfan syndrome Marfan Syndrome Marfan syndrome is a rare hereditary disorder of connective tissue, resulting in abnormalities of the eyes, bones, heart, blood vessels, lungs, and central nervous system. This syndrome is caused... read more Marfan Syndrome , Williams syndrome, and Noonan syndrome Noonan Syndrome Noonan syndrome is a genetic defect that causes a number of physical abnormalities, including short stature, heart defects, and an abnormal appearance. A gene is a segment of deoxyribonucleic... read more may cause birth defects that affect several organs, including the heart. Women over 35 years of age are at higher risk of having chromosomal abnormalities in the fetus. Even without a chromosomal abnormality, older maternal age appears to be a separate risk factor for heart birth defects. Older age of fathers may also contribute to birth defects of the heart.

When a family has had one child with a heart defect, the risk of a heart birth defect occurring in a subsequent pregnancy depends on the type of heart defect and whether there is a specific chromosome abnormality. Adults who were born with a heart defect should get tested for chromosome abnormalities and meet with a genetic counselor Genetic Counseling and Genetic Testing Before Pregnancy Genetic disorders are caused by abnormalities in one or more genes or chromosomes. Some genetic disorders are hereditary and others are spontaneous. Hereditary genetic disorders are passed down... read more to help them determine their risk of having a child with a heart defect.

Symptoms of Heart Defects

Sometimes heart defects cause few or no symptoms and are not detectable even during a physical examination of the child. Some mild defects cause symptoms only later in life. Fortunately, most serious heart defects in children are detectable based on symptoms noticed by parents and by abnormalities noticed during a doctor's examination.

Because normal circulation of 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 have difficulty feeding or may tire quickly during physical activities.

In more severe cases, breathing may be labored or a bluish color of the skin (cyanosis) may develop. Older children with heart defects may not be able to keep up with their peers during exercise or may experience shortness of breath, fainting, or chest pain, particularly during exercise.

Abnormal blood flow through the heart usually causes an abnormal sound (heart murmur) that can be heard using a stethoscope. Serious heart murmurs are often easy for a doctor to hear. However, the vast majority of heart murmurs that occur during childhood are not caused by heart defects and are not a sign of a problem. Murmurs that are not caused by a heart disorder are usually called innocent or functional murmurs.

Heart failure makes the heart beat rapidly and often causes fluid to collect in the lungs or liver. Fluid build up can lead to trouble breathing while eating, rapid breathing, grunting during breathing, crackling sounds in the lungs, an enlarged liver, and swelling of the legs.

Some heart defects (such as a hole in the atrium) increase the risk that a blood clot will form on the right side of the heart and pass across the defect, into the left side of the heart and then out to the body where it may block an artery in the brain, leading to a stroke Overview of Stroke A stroke occurs when an artery to the brain becomes blocked or ruptures, resulting in death of an area of brain tissue due to loss of its blood supply (cerebral infarction). Symptoms occur suddenly... read more . However, such blood clots are rare in childhood.

Did You Know...

  • The vast majority of heart murmurs that occur during childhood are not caused by heart defects and do not indicate any problems.

Eisenmenger syndrome

Eisenmenger syndrome occurs when a large left-to-right shunt Shunting of blood flow About one in 100 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... read more that is not corrected early in life leads to irreversible damage to the blood vessels of the lungs. This damage eventually leads to reversal of the shunt to one that is right-to-left.

Left-to-right shunting involves oxygen-rich blood, which is pumped from the left side of the heart, mixing with oxygen-poor blood being pumped through the pulmonary artery to the lungs. Left-to-right shunting makes the circulation inefficient and increases the amount of blood flowing to the lungs. Over time, this extra blood flow damages the lung blood vessels, causing the walls of the blood vessels to thicken abnormally. This may happen slowly, over many decades such as with an atrial septal defect 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. Holes can be present in the walls of the heart between the upper heart... read more Atrial and Ventricular Septal Defects or rapidly as occurs in persistent truncus arteriosus Persistent Truncus Arteriosus Persistent truncus arteriosus is a birth defect in which a single, large blood vessel (a truncus) exits the heart, instead of a separate pulmonary artery and aorta. The pulmonary artery comes... read more .

Eventually, the resistance to flow from the damaged and thickened lung arteries in the lungs can becomes so high that there is a reversal of blood flow from the right side of the heart to the left side. This reversal of blood flow is called Eisenmenger syndrome. Eisenmenger syndrome can overwork the right side of the heart, causing heart failure. Other complications include increasing bluish discoloration (cyanosis), abnormally increased thickness of the blood, bleeding from the lungs, and strokes.

Disorders that may lead to Eisenmenger syndrome include

Because birth defects of the heart are usually diagnosed and treated promptly, Eisenmenger syndrome is becoming less common.

Symptoms include a bluish color of the skin (cyanosis), widening and swelling of the fingernails or toenails (clubbing), fainting, shortness of breath during activity, fatigue, and chest pain. Other symptoms may develop, depending on which birth defect causes Eisenmenger syndrome.

If doctors suspect Eisenmenger syndrome, electrocardiography, echocardiography, and cardiac catheterization are done to provide more information about how the heart is functioning. Doctors also do laboratory tests to identify abnormalities caused by the lack of oxygen.

Although there are some interventions or medications that can delay the natural progression of this condition, heart and lung transplantation Lung and Heart-Lung Transplantation Lung transplantation is the surgical removal of a healthy lung or part of a lung from a living person and then its transfer into someone whose lungs no longer function. Heart-lung transplantation... read more is the only definitive treatment for Eisenmenger syndrome. Therefore, it is important that heart birth defects are identified and corrected as soon as possible.

Diagnosis of Heart Defects

  • Before birth, ultrasonography

  • Electrocardiography

  • Chest x-ray

  • Echocardiography

  • Cardiac catheterization

Many heart defects can be diagnosed before birth by using echocardiography Echocardiography and Other Ultrasound Procedures Ultrasonography is a type of medical imaging that uses high-frequency (ultrasound) waves to produce a moving image of internal organs and other tissues. Echocardiography is ultrasonography of... read more Echocardiography and Other Ultrasound Procedures (ultrasonography of the heart). If a heart defect is diagnosed or suspected by the obstetrician, the mother is often referred for a specialized ultrasound examination called fetal echocardiography. This procedure allows the fetus's heart to be examined in detail. When a serious heart defect is confirmed, plans can be made for optimal care of the newborn immediately after birth.

In the United States and many other countries, newborns are screened for heart defects when they are one or two days old. Screening is done with a pulse oximeter (a painless test that checks oxygen levels in the blood using a sensor applied to the skin). Heart defects that are not detected before or right after birth are suspected in newborns or young children when symptoms develop, when abnormal heart murmurs are heard when a doctor listens to the heart with a stethoscope, or when other signs of a heart condition are recognized.

Treatment of Heart Defects

  • Open-heart surgery

  • Cardiac catheterization procedures

  • Medications

  • Extracorporeal membrane oxygenation (ECMO) and ventricular assist devices (VADs)

  • Rarely a heart transplant

Immediate care

Heart failure or cyanosis that occurs in the first week of life is a medical emergency. Doctors often insert a thin tube (a catheter) in the newborn's vein within the umbilical cord to make giving medications easier and faster. Medications, are given by vein to reduce the workload of the heart and to improve the amount of oxygen that can be delivered to the body. In newborns, prostaglandins can be life saving in certain critical heart defects that require the ductus arteriosus to stay open. Newborns may also need a ventilator to help them breathe. When certain defects are present, newborns are sometimes also given oxygen.

Open-heart surgery

Many serious heart defects can be effectively repaired with open-heart surgery. The timing of the operation depends on the specific defect, its symptoms, and the severity. However, infants with severe symptoms resulting from a heart defect should have surgery during the first days or weeks of life.

The repair of some complicated heart defects may be too difficult in the first few weeks and a non-open-heart procedure may need to be done to stabilize the infant's condition and delay the need for a more corrective operation. An example of this type of operation would be creation of a shunt between the aorta and the pulmonary artery.

Cardiac catheterization

Cardiac catheterization is a procedure in which a thin tube (catheter) is inserted into a vein or artery in the groin and advanced to the heart for diagnosis or treatment. Other approaches to the heart are sometimes used, including the umbilical (belly button) vein or artery in the newborn.

Narrowed structures can sometimes be widened by passing a catheter into the narrowed area of the heart. A balloon attached to the catheter is inflated and widens the narrowing, usually in a valve (a procedure called balloon valvuloplasty) or blood vessel (balloon angioplasty). These balloon procedures may be done instead of open-heart surgery or may delay the need for open-heart surgery.

In some newborns, such as those with transposition of the great arteries 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. The aorta and pulmonary artery are reversed, which causes oxygen-poor... read more Transposition of the Great Arteries , a procedure called balloon atrial septostomy can be done during a cardiac catheterization. In this situation, a balloon is used to enlarge the foramen ovale (hole between the upper chambers of the heart) to help improve oxygen flow to the body. This procedure is usually done to stabilize the baby before open-heart surgery.

Medications

In a newborn, when blood flow to the body or to the lungs is severely blocked, a type of medication called a prostaglandin can be given to keep the ductus arteriosus open, which can be life-saving.

Other medications that are commonly used in children with a heart defect include

  • A diuretic, such as furosemide, which helps to remove excess fluid from the body and lungs

  • Angiotensin-converting enzyme (ACE) inhibitors, such as captopril, enalapril, or lisinopril (which relax blood vessels and help the heart to pump more easily)

  • Digoxin, which helps the heart to pump a bit more forcefully

  • Milrinone, a powerful drug given by vein (intravenously) to stimulate the heart to beat more strongly and relax tight blood vessels

Devices to support heart function

Mechanical devices may be used to support the heart in children who have severe heart failure and do not respond to medication. These devices have a pump that helps to send enough blood to the lungs and to the body when the heart is unable to pump effectively. They can be used for days, weeks, or even months to allow a child's heart to recover from a viral infection or major open-heart surgery or to help stabilize the child until a heart transplant can be done.

In extracorporeal membrane oxygenation (ECMO), blood from the child is circulated through a machine that adds oxygen and removes carbon dioxide and then pumps that blood to the child's body.

Some devices, called ventricular assist devices (VADs) can be inserted into the body. A VAD pumps blood from the heart to the body. This device allows for longer support of the circulation than ECMO.

Heart transplantation

Long-term management

Children with a weak heart muscle or residual valve problems after surgery require long-term treatment with medications and changes to their diet (such as salt restriction and use of a high-calorie formula in a relatively small amount of liquid). These treatments decrease the workload of the heart.

Some children who have significant heart defects or have had surgeries to repair their heart defects need to take antibiotics before visits to the dentist and before certain surgeries (such as on the respiratory tract). These antibiotics are used to prevent a serious heart infection called endocarditis Infective Endocarditis Infective endocarditis is an infection of the lining of the heart (endocardium) and usually also of the heart valves. Infective endocarditis occurs when bacteria enter the bloodstream and travel... read more Infective Endocarditis . However, most children with heart defects, whether or not they had surgery, do not require these antibiotics. However, all children with heart defects, should take good care of their teeth and gums to decrease the risk of infection spreading to their heart.

More Information

The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Eskalith, Eskalith CR, Lithobid
Absorica, Absorica LD, Accutane, Amnesteem , Claravis , MYORISAN, Sotret, ZENATANE
Delone , FUROSCIX, Lasix
Capoten
Epaned, Vasotec
Prinivil, QBRELIS, Zestril
Digitek , Lanoxicaps, Lanoxin, Lanoxin Pediatric
Primacor
NOTE: This is the Consumer Version. DOCTORS: VIEW PROFESSIONAL VERSION
VIEW PROFESSIONAL VERSION
quiz link

Test your knowledge

Take a Quiz!
iOS ANDROID
iOS ANDROID
iOS ANDROID
TOP