Congenital heart defects are abnormalities in the heart's structure that are present at birth. Approximately 8 out of every 1,000 newborns have congenital heart defects, ranging from mild to severe. Congenital heart defects happen because of incomplete or abnormal development of the fetus' heart during the very early weeks of pregnancy. Some are known to be associated with genetic disorders, such as Down syndrome, but the cause of most congenital heart defects is unknown. While they can't be prevented, there are many treatments for the defects and any related health problems.
How a Healthy Heart Works
To understand more about congenital heart defects, it's helpful to understand how a healthy heart works.
The heart, lungs, and blood vessels make up the circulatory system of the human body. The heart is the central pump of the circulatory system, and consists of four chambers — the left atrium and left ventricle and the right atrium and right ventricle.
The heart also has four valves that direct the flow of blood through the heart:
- The left atrium of the heart receives oxygen-rich blood from the lungs and then empties into the left ventricle through the mitral valve.
- The left ventricle pumps oxygen-rich blood out to the rest of the body. Blood leaves the left ventricle through the aortic valve and enters the aorta, the largest artery (a blood vessel that carries oxygenated blood) in the body. Blood then flows from the aorta into the branches of many smaller arteries, providing the body's organs and tissues with the oxygen and nutrients they need.
- After oxygen in the blood is released to the tissues, the now deoxygenated (oxygen-poor) blood returns to the heart through veins, the blood vessels that carry deoxygenated blood. This blood, which appears blue, enters the right atrium of the heart and then travels across the tricuspid valve into the right ventricle.
- The right ventricle then pumps deoxygenated blood through the pulmonic valve into the lungs. The oxygen in the air we breathe binds to cells within this blood that is being pumped through the lungs. The oxygen-rich blood, which appears red, then returns to the left atrium and enters the left ventricle, where it is pumped out to the body once again.
This is the normal pathway that blood travels through the heart and the body. However, abnormalities in the heart's structure — such as congenital heart defects — can affect its ability to function properly.
Common Heart Defects
Common types of congenital heart defects, which can affect any part of the heart or its surrounding structures, include:
Aortic Stenosis
In aortic stenosis, the aortic valve is stiffened and has a narrowed opening (a condition called stenosis). It does not open properly, which increases strain on the heart because the left ventricle has to pump harder to send blood out to the body. Sometimes the aortic valve also does not close properly, causing it to leak, a condition called aortic regurgitation.
Atrial Septal Defect (ASD)
ASD is a hole in the wall (called the septum) that separates the left atrium and the right atrium.
Atrioventricular Canal Defect
This defect — also known as endocardial cushion defect or atrioventricular septal defect — is caused by a poorly formed central area of the heart. Typically there is a large hole between the upper chambers of the heart (the atria) and, often, an additional hole between the lower chambers of the heart (the ventricles). Instead of two separate valves allowing flow into the heart (tricuspid on the right and mitral valve on the left), there is one large common valve, which may be quite malformed. Atrioventricular canal defect is commonly seen in children with Down syndrome.
Coarctation of the Aorta (COA)
COA is a narrowing of a portion of the aorta, and often seriously decreases the blood flow from the heart out to the lower portion of the body.
Hypoplastic Left Heart Syndrome
When the structures of the left side of the heart (the left ventricle, the mitral valve, and the aortic valve) are underdeveloped, they're unable to pump blood adequately to the entire body. This condition is usually diagnosed within the first few days of life, at which point the baby may be critically ill.
Fortunately, many of these infants are recognized to have serious heart disease even before birth on ultrasound tests. A fetal echocardiogram is a specialized ultrasound that allows doctors to see the baby's heart in great detail and plan the best care for the baby while still in utero.
Patent Ductus Arteriosus (PDA)
The ductus arteriosus (DA) is a normal blood vessel in the developing fetus that diverts circulation away from the lungs and sends it directly to the body. (The lungs are not used while the unborn fetus is in amniotic fluid — the fetus gets oxygen directly from the mother's placenta.) The DA usually closes on its own shortly after birth; it is no longer needed once a newborn breathes on his own. If the DA doesn't close, then a condition called patent ductus arteriosus (PDA) results, which can result in too much blood flow to a newborn's lungs. PDA is common in premature babies.
Pulmonary Atresia
In this defect the pulmonic valve does not open at all and may indeed be completely absent. The main blood vessel that runs between the right ventricle and the lungs also may be malformed and the right ventricle can be abnormally small.
Pulmonary Stenosis
In pulmonary stenosis, the pulmonic valve is stiffened and has a narrowed opening (a condition called stenosis). It does not open properly, which increases strain on the right side of the heart because the right ventricle has to pump harder to send blood out to the lungs.
Tetralogy of Fallot (TOF)
Tetralogy of Fallot is actually a combination of four heart defects. It includes pulmonary stenosis, a thickened right ventricle (known as ventricular hypertrophy), a hole between the lower chambers (known as a ventricular septal defect), and an aorta that can receive blood from both the left and right ventricles, instead of draining just the left. Because deoxygenated (blue) blood can flow out to the body, children with this defect often appear bluish.
Total Anomalous Pulmonary Venous Connection
The pulmonary veins normally are the blood vessels that deliver oxygenated blood from the lungs to the left atrium. Sometimes these vessels don't join the left atrium during development. Instead they deliver blood to the heart by other pathways, which may be narrowed. Pressure builds up in this pathway and in the pulmonary veins, pushing fluid into the lungs, decreasing the amount of oxygenated blood that reaches the body. These infants often have difficulty breathing and appear bluish.
Transposition of the Great Arteries
In this condition, the pulmonary artery and the aorta (the major blood vessels leaving the heart) are switched so that the aorta arises from the right side of the heart and receives blue blood, which is sent right back out to the body without becoming oxygen-rich. The pulmonary artery arises from the left side of the heart, receives red blood and sends it back to the lungs again. The result is that babies with this condition often appear very blue and have low oxygen levels in the bloodstream. They usually come to medical attention within the first days of life.
Tricuspid Atresia
Blood normally flows from the right atrium to the right ventricle through the tricuspid valve. In tricuspid atresia, the valve is replaced by a plate or membrane that does not open. The right ventricle therefore does not receive blood normally and is often small.
Truncus Arteriosus
In an embryo, the aorta and the pulmonary artery are initially a single vessel. During normal development, that vessel splits to form the two major arteries. If that split does not occur, the child is born with a single common great blood vessel called the truncus arteriosus. There is usually a hole between the ventricles associated with this defect.
Ventricular Septal Defect (VSD)
One of the most common congenital heart defects, VSD is a hole in the wall (septum) between the heart's left and right ventricles. These can occur at different locations and vary in size from very small to very large. Some of the smaller defects may gradually close on their own.
Signs and Symptoms of Heart Defects
Because congenital defects often compromise the heart's ability to pump blood and to deliver oxygen to the tissues of the body, they often produce telltale signs such as:
- a bluish tinge or color (cyanosis) to the lips, tongue and/or nailbeds
- an increased rate of breathing or difficulty breathing
- poor appetite or difficulty feeding (which may be associated with color change)
- failure to thrive (failure to gain weight or weight loss)
- abnormal heart murmur
- sweating, especially during feedings
- diminished strength of the baby's pulse
If you notice any of these signs in your baby or child, call your doctor right away. If your doctor notices these signs, you may be referred to a pediatric cardiologist.
Diagnosing a Heart Defect
If a congenital defect is suspected, your doctor may refer you to a pediatric cardiologist. Some congenital heart defects cause serious symptoms right at birth, requiring newborn intensive care in the hospital and immediate evaluation by a cardiologist. Other defects, like small atrial septal defects, may go undiagnosed until the teen — or even adult — years.
After a complete physical examination, including evaluation of the baby's heart rate and blood pressure, the cardiologist probably will order a chest X-ray to evaluate the size and shape of the heart and to view the lungs.
An electrocardiogram (EKG) is usually done, too. EKGs are performed by placing small pads (called leads) on your child's chest, which are wired to a monitor that records and prints out the electrical signals of the heart.
The cardiologist will often order an echocardiogram, which provides detailed images of the heart by using ultrasound. Specialized ultrasound waves can demonstrate all of the heart chambers and valves, the great arteries arising from the heart, and the direction and speed of blood flow in various areas of the heart. Echocardiograms can also evaluate whether the heart is squeezing and relaxing normally. Echocardiograms are the primary tool for diagnosing congenital heart defects.
A fetal echocardiogram is a specialized type of ultrasound that allows diagnosis of heart problems in utero. This can be done as early as 16-18 weeks' gestation. These tests are usually ordered when an obstetrician suspects a heart abnormality on a level II ultrasound. They are also often ordered if there is another close family member with a congenital heart defect or when mom has a condition, such as diabetes, which may predispose a heart problem in the fetus.
Cardiac catheterization is sometimes performed as well. During this procedure, a long, thin tube called a catheter is threaded through blood vessels in the navel (in a newborn) or the groin and up into the heart. Once in place, the catheter can measure the oxygen levels and pressures within the heart's chambers. Dye may be injected through the catheter to better illustrate the heart's inner structures and determine the direction of blood flow through the heart. Nowadays, a number of congenital heart defects can be fixed in the cardiac catheterization laboratory. For instance, there are devices that can be used to close holes in the heart or to open up tight valves or narrowed blood vessels.
A pediatric cardiologist is the doctor most qualified to diagnose a congenital heart defect and provide treatment. This is true even before a baby is born. If you are an expectant parent and your baby has been diagnosed with a congenital heart defect via a fetal ultrasound, consult a pediatric cardiologist.
If You Suspect a Problem
If you think your child may have a congenital heart defect or you notice any signs (such as difficulty breathing or feeding, or bluish skin) that concern you, call your doctor. In more urgent cases, such as if your baby suddenly turns blue or stops breathing, call 911.
Today there are more treatment options for congenital heart defects than ever before, and most defects are treated successfully. If you suspect that your child has a heart defect, the sooner you get medical attention, the better chance your child will have of making the fullest recovery possible.
With all the medical resources available, a congenital heart defect does not necessarily mean a child cannot lead a normal life. Working with your doctor, you'll get the best care for your child.