What is congenital heart disease?

Congenital heart disease is the most common of all major birth defects. A congenital heart defect occurs when the heart or blood vessels near the heart do not develop normally before birth. These defects can involve:

  • A hole in the heart (Septal Defect)
  • Narrowed Valves
  • Defects that affect blood flow to or from the heart (i.e., tetralogy of Fallot)
  • Defects that affect the heart muscle, such as in cardiomyopathy


Atrial Septal Defect

Congenital means inborn or existing at birth. Other names for congenital heart disease are congenital heart defect and congenital cardiovascular disease.

About 1 million Americans with congenital heart defects are alive today.1

For more information on how a healthy heart works, go to How Your Heart Works.

Types of Congenital Heart Defects
There are many types of congenital heart defects. Some are simple, such as a hole in the wall (septum) that separates the right side of the heart from the left side of the heart. Other defects involve a narrowed heart valve that blocks blood flow to the lungs or other parts of the body.

A Hole in the Heart (Septal Defect)
The septum is the wall that separates the heart into left and rights sides. The wall prevents mixing of blood between the two sides of the heart. Sometimes, a baby is born with a hole in the septum. The hole allows blood to mix between the two sides of the heart.

Atrial septal defect (ASD): 
An ASD is a hole in the part of the septum that separates the atria—the upper chambers of the heart. This heart defect allows oxygen-rich blood from the left atrium to flow across into the right atrium instead of flowing down to the left ventricle as it should. Many children who have ASDs have few, if any, symptoms.

An ASD can be small or large. Small ASDs allow only a little blood to leak from one atrium to the other. Very small ASDs don't affect the way the heart works and don't require any treatment. Many small ASDs close on their own as the heart grows during childhood.

Ventricular septal defect (VSD): 
A VSD is a hole in the part of the septum that separates the ventricles—the lower chambers of the heart. The hole allows oxygen-rich blood to flow from the left ventricle over into the right ventricle instead of flowing into the aorta and out to the body as it should.

A small VSD doesn't cause problems and may close on its own. Large VSDs cause the left side of the heart to work too hard. This increases blood pressure in the right side of the heart and the lungs because of the extra blood flow. The increased work of the heart can cause poor growth and heart failure. Open-heart surgery is used to repair VSDs.

Narrowed Valves

Simple congenital heart defects also can involve the heart's valves. These valves control the flow of blood from the atria to the ventricles and from the ventricles into the two large arteries connected to the heart (the aorta and the pulmonary artery). Valves can have the following types of defects:

  • Stenosis (ste-NO-sis). This is when the valve does not open completely, and the heart has to work harder to pump the blood through the valve.
  • Atresia (a-TRE-ze-AH). This is when the valve does not form correctly, so there is no opening for blood to pass.
  • Regurgitation (re-GUR-ji-TA-shun). This is when the valve does not close completely, so blood leaks back through the valve.

The most common valve defect is called pulmonary valve stenosis, which is a narrowing of the pulmonary valve. This valve allows blood to flow from the right ventricle into the pulmonary arteries and out to the lungs to pick up oxygen. Pulmonary valve stenosis can range from mild to severe. Most children with this defect have no signs or symptoms other than a heart murmur. Treatment isn’t needed if the stenosis is mild.

Defects that Affect Blood Flow to and From the Heart
The most common complex heart defect is tetralogy of Fallot (teh-TRAL-o-je of fah-LO), a combination of four defects:

  • Pulmonary valve stenosis.
  • A large Ventricular Septal Defect (VSD).
  • An overriding aorta. In this defect, the aorta sits above both the left and right ventricles over the VSD, rather than just over the left ventricle. As a result, oxygen-poor blood from the right ventricle can flow directly into the aorta instead of into the pulmonary artery to the lungs.
  • Right ventricular hypertrophy. In this defect, the muscle of the right ventricle is thicker than usual because of having to work harder than normal.

Together, these four defects mean that not enough blood is able to reach the lungs to get oxygen, and oxygen-poor blood flows out to the body.

Complex congenital heart defects need to be repaired with surgery.