What is a Congenital Heart Defect? What is a Congenital Heart Defect?
National Heart, Lung, and Blood Institute

The term “congenital heart defect” indicates that a structural problem (or defect) in a baby’s heart is present at birth. A baby’s heart begins to form shortly after conception. By the end of the 2nd month of pregnancy, the baby’s heart is completely formed. It is during this time that a congenital heart defect can occur. In this case, a part of the heart, heart valves, and/or blood vessels near the heart do not develop properly. When this happens, blood flow can:

Slow down
Go in the wrong direction or to the wrong place
Be blocked completely.
Congenital heart defects are the most common type of major birth defect. More than 30,000 babies are born with a congenital heart defect in the United States each year.

Types of Congenital Heart Defects
There are many types of congenital heart defects. They are:

Abnormal passages in the heart or between blood vessels
Problems with the heart valves
Problems with the placement or development of blood vessels near the heart
Problems with development of the heart itself.
To better understand the effects of these problems, go to the section on “How the Heart Works.”

Some of these problems are described below.

Abnormal Passages in the Heart or Blood Vessels
Atrial septal defect (ASD) is a hole in the wall that separates the upper chambers (atria) of the heart. This causes blood to leak from one atrium to the other.

Ventricular septal defect (VSD) is a hole in the wall that separates the lower chambers (ventricles) of the heart. This causes blood to leak from one ventricle to the other.

Atrioventricular septal defect (AVSD) includes an ASD, VSD, and abnormal development of the atrioventricular valves (tricuspid and mitral). This causes blood to flow abnormally inside the heart. An AVSD is also known as an atrioventricular canal defect.

Patent ductus arteriosus (PDA) is a persistent connection between the aorta and the pulmonary artery. This connection is called the ductus arteriosus and is normally present before birth. In most babies, the vessel closes within a few hours to days after birth. In some children, this vessel fails to close.
Problems with the Heart Valves
Heart and valve abnormalities can affect any of the valves and include the following:

Stenosis: The valve opening is narrow and does not open completely.

Atresia: The valve is not formed so that there is not communication for blood to pass from one chamber to another.

Regurgitation: The valve does not close completely causing blood to leak back.
Examples of heart valve problems include:

Aortic valve stenosis is a defect of the aortic valve in the heart that often causes it to open incompletely. This reduces blood flow to the body.

Pulmonary valve atresia is a defect where a solid sheet of tissue forms instead of the pulmonary valve. This prevents oxygen-poor blood in the right side of the heart from traveling normally to the lungs to pick up oxygen.

Pulmonary valve stenosis is a narrowing of the pulmonary valve. This slows the flow of blood from the right side of the heart to the lungs. The heart must pump harder to push blood through the smaller opening to the lungs where the blood picks up oxygen.

Tricuspid atresia is a defect where a solid sheet of tissue forms instead of the tricuspid valve. The tricuspid valve is between the right atrium (the upper chamber) and right ventricle (the lower chamber) of the heart. Without the tricuspid valve, oxygen-poor or blue blood entering the right atrium cannot travel normally to the lungs to pick up oxygen.

Ebstein’s anomaly is a defect where the tricuspid valve is both displaced and abnormally formed. The valve is leaky and allows blue blood to flow back into the right atrium instead of to the lungs to pick up oxygen.
Problems with Placement or Development of Blood Vessels near the Heart
Transposition of the great vessels is a defect where the location of the “great vessels” (the aorta and pulmonary artery) coming off the heart is switched. The aorta comes off the right ventricle instead of the left ventricle. The pulmonary artery arises from the left ventricle instead of the right ventricle. Therefore, blood without oxygen is continually pumped to the body, instead of blood with oxygen.

Tetralogy of Fallot is a combination of four defects:
Pulmonary valve stenosis is the narrowing of the pulmonary valve that slows the flow of blood from the right ventricle to the lungs.
VSD is a hole in the wall that separates the left and right ventricles.
Overriding aorta is a defect where the aorta is positioned between the left and right ventricles, over the VSD.
Right ventricular hypertrophy is the thickening of the right ventricle. It is caused by the heart having to work harder because of the other defects.

Truncus arteriosus is a defect of the great vessels (aorta and pulmonary artery). The aorta and pulmonary artery do not form as separate arteries. Instead, a large artery, called the truncus, comes from the heart. As the truncus leaves the heart, it may branch into arteries that carry blood to the body and to the lungs.

Coarctation of the aorta is a narrowing of the aorta. It slows or blocks the flow of blood from the heart to the body.

Anomalous pulmonary venous return is a defect where 1 or more of the 4 pulmonary veins that normally return oxygen-rich or red blood from the lungs to the heart, return to the wrong chamber in the heart.
Problems with Development of the Heart
Hypoplastic left heart syndrome* is a combination of defects where the left side of the heart does not develop properly. Usually there is mitral atresia, aortic atresia, and a tiny left ventricle.
Mitral atresia occurs when a solid sheet of tissue forms instead of the mitral valve, which separates the left atrium and the left ventricle.
Aortic atresia occurs when a solid sheet of tissue forms instead of the aortic valve, which separates the left ventricle from the aorta.

Single ventricle* describes a group of heart defects where only one ventricle is present instead of two. It can be a single right or a single left ventricle. The other ventricle is usually absent or very tiny. Hypoplastic left heart syndrome is an example of a single ventricle defect.
Today, the outlook for an infant born with a heart defect is much better than it was 30 years ago. Rapid advances in infant and childhood surgery, better tests, and new medicines help most children with congenital heart defects. Many children born with more complex or severe heart defects now reach adulthood. Today, there are more than 1 million adults living with congenital heart disease.

Other Names for Congenital Heart Defects
Congenital heart disease
Cyanotic heart disease
Heart defects
Congenital cardiovascular malformations


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