- Normal Fetal Circulation
- Types of Heart Defects
- Resources In This Article
Overview of 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.
Detectable symptoms include poor feeding, trouble breathing, bluish skin, inability to grow or exercise normally, rapid heart beat, fainting and, when the infant gets older, chest pain during exercise.
During examination, a doctor may notice a heart murmur or other abnormal sound, a rapid heart beat, rapid or labored breathing, weak pulses, and/or a large liver.
Ultrasonography 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 drugs.
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). 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.
The fetus is in the uterus, where there is no air to breathe. Instead, the fetus gets oxygen-filled blood from the mother's placenta through the umbilical cord, and the lungs are filled with fluid. 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 blood from the veins (venous blood) coming to the right side of the heart bypasses the fluid-filled lungs and travels through two different short-cuts to get to the fetus' body. These short-cuts are
These short-cuts allow venous blood to mix with blood that has already traveled to the lungs. 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. This 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
Abnormally formed hearts alter the normal blood flow to the lungs and body by
Shunting is usually classified as from
Right-to-left shunting involves oxygen-poor blood from the right side of the heart mixing with oxygen-rich blood 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. A birth defect of the heart that often causes cyanosis is tetralogy of Fallot.
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 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 the right side of the heart, causing heart failure (see Figure: Heart Failure: Pumping and Filling Problems). Examples of disorders in which left-to-right shunting occurs are ventricular septal defects, atrial septal defects, patent ductus arteriosis, and atrioventricular septal defects.
In 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 and the pulmonary artery, which supplies the lungs, connects to the left 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 hours of birth.
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)
Into the heart because of narrowing of the tricuspid valve (on the right side of the heart) or the mitral valve (on the left side of the heart)
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 may back up into 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).
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 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. Abnormal heart murmurs are often loud or harsh sounding. 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. Fluid build up can lead to rapid breathing, grunting during breathing, crackling sounds in the lungs, and an enlarged liver.
Some heart defects (such as a hole in the atrium) increase the risk that a blood clot will form and block an artery in the brain, leading to a stroke. However, such blood clots are rare in childhood.
Many heart defects can be diagnosed before birth by using ultrasonography. 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. Heart defects that are not detected before 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.
Diagnosing heart defects in children involves the same techniques used for diagnosing heart problems in adults. A doctor may be able to diagnose the defect after asking the family specific questions and doing a physical examination, electrocardiography (ECG), and a chest x-ray.
Ultrasonography of the heart (echocardiography) is used to diagnose almost all of the specific defects.
Cardiac catheterization can provide details of the abnormality and also can be used to treat some heart defects.
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 drugs easier and quicker. Drugs, such as a prostaglandin, are given by vein to reduce the workload of the heart. Newborns may also need a ventilator to help them to breathe. When certain defects are present, newborns are sometimes also given oxygen.
Many serious heart defects are effectively repaired with open-heart surgery. The timing of the operation depends on the specific defect, its symptoms, and the severity. When possible, it is often better to postpone surgery until the child is a little older. However, infants with severe symptoms resulting from a heart defect should have surgery during the first days or weeks of life.
Narrowed structures can sometimes be widened by passing a catheter through a blood vessel in the groin, neck, arm, or even the belly button into the narrowed area of the heart. Passing a catheter into the heart is called cardiac catheterization. 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). These balloon procedures may be done instead of open-heart surgery or may delay the need for open-heart surgery. Cardiac catheterization can also be used to close a patent ductus arteriosus or certain holes in the heart (many atrial septal defects and some ventricular septal defects) by inserting a plug or other specialized device through the catheter. Cardiac catheterization does not leave a large scar on the skin, and the recovery time is often shorter than recovery after open-heart surgery.
In some newborns, such as those with 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.
When blood flow to the body or to the lungs is severely blocked, a drug called prostaglandin can be given to keep the ductus arteriosus open, which can be life-saving.
Other drugs 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
In recent years, sophisticated mechanical devices have been used to support the heart in children who have severe heart failure and do not respond to drugs. These devices have a pump that helps to send enough blood flow 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 newborn is circulated through a machine that adds oxygen and removes carbon dioxide and then returns the blood to the newborn.
Some devices, called ventricular assist devices (VADs) can be inserted into the body. A VAD pumps blood from the heart to the body.
Treatment of older infants and children includes drugs 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 bowel or bladder). These antibiotics are used to prevent serious heart infections called endocarditis. All children with heart defects, should take good care of their teeth and gums to decrease the risk of infection spreading to their heart.