Congenital heart defects / Cardiac Anomalies

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, which can range 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:

1. The left atrium of the heart receives oxygen-rich blood from the lungs and then empties into the left ventricle through the mitral valve.

2. 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.

3. 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.

4. 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.

Classification
A number of classification systems exist for congenital heart defects. In 2000 the International Congenital Heart Surgery Nomenclature was developed to provide a generic classification system.

1.Hypoplasia
Hypoplasia can affect the heart, typically resulting in the underdevelopment of the right ventricle or the left ventricle. This causes only one side of the heart to be capable of pumping blood to the body and lungs effectively. Hypoplasia of the heart is rare but is the most serious form of CHD. It is called hypoplastic left heart syndrome when it affects the left side of the heart and hypoplastic right heart syndrome when it affects the right side of the heart. In both conditions, the presence of a patent ductus arteriosus (and, when hypoplasia affects the right side of the heart, a patent foramen ovale) is vital to the infant’s ability to survive until emergency heart surgery can be performed, since without these pathways blood cannot circulate to the body (or lungs, depending on which side of the heart is defective). Hypoplasia of the heart is generally a cyanotic heart defect.

2.Obstruction defects
Obstruction defects occur when heart valves, arteries, or veins are abnormally narrow or blocked. Common defects include pulmonic stenosis, aortic stenosis, and coarctation of the aorta, with other types such as bicuspid aortic valve stenosis and subaortic stenosis being comparatively rare. Any narrowing or blockage can cause heart enlargement or hypertension.

3.Septal defects
The septum is a wall of tissue which separates the left heart from the right heart. Defects in the interatrial septum or the interventricular septum allow blood to flow from the right side of the heart to the left, reducing the heart’s efficiency. Ventricular septal defects are collectively the most common type of CHD,although approximately 30% of adults have a type of atrial septal defect called probe patent foraman ovale.

4.Cyanotic defects
Cyanotic heart defects are called such because they result in cyanosis, a bluish-grey discoloration of the skin due to a lack of oxygen in the body. Such defects include persistent truncus arteriosus, total anomalous pulmonary venous connection, tetralogy of Fallot, transposition of the great vessels, and tricuspid atresia.

Causes

Congenital heart disease is caused by a congenital heart defect. Often, the two terms are used interchangeably. According to the March of Dimes, one in 125 babies born in the United States has a congenital heart defect. In fact, these are the most common type of all birth defects. Although doctors sometimes don’t know the cause of the heart defect, suspected causes include:

– genetics: the defect may run in families
– medications: some drugs taken during pregnancy can increase the risk, such as anti-seizure medications
– alcohol or drug abuse during pregnancy
– infections: if the mother had a viral infection in the first trimester, it may increase the risk of giving birth to a child with a heart defect
– diabetes: may affect childhood development. Gestational diabetes so far hasn’t been linked to congenital heart disease

Common Heart Defects
Common types of congenital heart defects, which can affect any part of the heart or its surrounding structures, include:
1. Adult Congenital Heart Disease
Children who were treated for a congenital heart defect when they were little may think they do not need any further follow-up with a cardiologist. But that’s not always true. Even those who were successfully treated as children may experience complications at different times throughout their life. These issues may vary in severity, depending on the defect. Read more

2. 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.

3. Atrial Septal Defect (ASD)
ASD is a hole in the wall (called the septum) that separates the left atrium and the right atrium. This wall is called the atrial septum. When this hole is present, it allows extra blood flow to travel from the left atrium into the right heart and out to the lungs.

4. 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.

5. Coarctation of the Aorta (COA)
Coarctation of the aorta 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.

6. 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.

7. 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 independently. Patent ductus arteriosus (PDA) occurs when the DA doesn’t close, which can result in too much blood flow to a newborn’s lungs. PDA is common in premature babies.

8. Patent Foramen Ovale (PFO)
The patent foramen ovale is a normal hole between the upper chambers of the heart. It is present in the unborn fetus and usually seals up in the first few months of life. In approximately 25% of people, this hole never fully closes. Usually, it does not cause problems and does not require treatment.

9.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 might be malformed and the right ventricle can be abnormally small. These babies usually appear blue (cyanotic) after birth and need immediate specialized care.

10. Pulmonary Stenosis
In pulmonary stenosis, the pulmonic valve is stiffened and has a narrowed opening (called stenosis). It does not open properly, which may increase strain on the right side of the heart because the right ventricle has to pump harder to send blood out to the lungs. If mild, pulmonary stenosis may never require any treatment.

11. Tetralogy of Fallot (TOF)
Tetralogy of Fallot is actually a combination of four heart defects: pulmonary stenosis; a thickened right ventricle (ventricular hypertrophy); a hole between the lower chambers (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.

12. 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.

13. 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. As a result, 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 after birth.

14. 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.

15. 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, the aorta and the pulmonary artery. If that split does not occur, the child is born with a single common great blood vessel called the truncus arteriosus. There usually is a hole between the ventricles associated with this defect. The valve leading into the truncus arteriosus may be very abnormal.

16. 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 tell tale signs such as:

– a bluish tinge or color (cyanosis) to the lips, tongue, and/or nail beds
– an increased rate of breathing or difficulty breathing
– poor appetite or difficulty feeding (which may be associated with color change)
– failure to thrive (weight loss or failure to gain weight)
– abnormal heart murmur
– sweating, especially during feeding
– 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 heart defect is suspected, your doctor will likely 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 an electrocardiogram (EKG). EKGs are performed by placing small pads (called leads) on the 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 also can 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’re also ordered if another close family member has a congenital heart defect or when the mother has a condition, such as diabetes, that might make a heart problem in the fetus more likely.

In some children, a chest X-ray is done to evaluate the size and shape of the heart. It can also help show the amount of blood the heart is pumping to the lungs.

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.

Many congenital heart defects can be fixed in the cardiac catheterization laboratory. For instance, devices can close holes in the heart or 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, your obstetrician probably will arrange a consultation with a paediatric cardiologist.

Prevention

Women who are pregnant can take certain precautions to lower their risk of giving birth to a baby with a congenital heart defect:

1. If you’re planning on become pregnant, talk to your doctor about any medications you’re taking.
2. Avoid alcohol and illegal drugs during pregnancy.
3. If you have diabetes, make sure your blood sugar levels are under control before becoming pregnant and work with your doctor to manage the disease while pregnant.
4. If you weren’t vaccinated against rubella (German measles), avoid exposure to the disease and talk to your doctor about prevention options