Symptoms

How congenital heart defects develop

During the first six weeks of pregnancy, the heart begins to form and starts beating. The major blood vessels that run to and from the heart also begin to develop during this critical time.

It's at this point in your baby's development that heart defects may begin to develop. Researchers aren't sure exactly what causes most of these defects, but they think genetics, certain medical conditions, some medications, and environmental or lifestyle factors, such as smoking, may play a role.

There are many different types of congenital heart defects. They fall into the general categories described below.

Abnormal connections in the heart or blood vessels

Abnormal connections allow blood to flow where it normally wouldn't. Holes in the walls between heart chambers are an example of congenital heart defects that involve an abnormal connection.

An abnormal connection can cause oxygen-poor blood to mix with oxygen-rich blood. This lowers the amount of oxygen sent through your child's body. Your child's skin or fingernails may look blue or pale gray (dusky). The heart and lungs have to work harder to accommodate abnormal blood flow.

Types of abnormal connections in the heart or blood vessels include:

• Atrial septal defect is a hole between the upper heart chambers (atria).
• Ventricular septal defect is a hole in the wall between the right and left chambers on the lower half of the heart (ventricles).
• Patent ductus arteriosus (PAY-tunt DUK-tus ahr-teer-e-O-sus) is a connection between the lung artery and the body's main artery (aorta). It's open while a baby is growing in the mother's womb, and normally closes a few hours after birth. But in some babies, it remains open, causing abnormal blood flow between the two arteries.
• Total or partial anomalous pulmonary venous connection occurs when all or some of the blood vessels from the lungs (pulmonary veins) attach to a wrong area or areas of the heart.

Congenital heart valve problems

Heart valves are like doorways between the heart chambers and the blood vessels. Heart valves open and close to keep blood moving in the correct direction. If the heart valves can't open and close correctly, blood can't flow smoothly.

Heart valve problems include valves that are narrowed and don't open completely (stenosis) or valves that don't close completely (regurgitation).

Examples of congenital heart valve problems include:

• Aortic stenosis (stuh-NO-sis). A baby may be born with an aortic valve that has one or two valve flaps (cusps) instead of three. This creates a smaller, narrow opening for blood to pass through. The heart must work harder to pump blood through the valve. Eventually, this leads to enlarging of the heart and thickening of the heart muscle.
• Pulmonary stenosis. A defect on or near the pulmonary valve narrows the pulmonary valve opening and slows the blood flow.
• Ebstein anomaly. The tricuspid valve — which is located between the right upper heart chamber (atrium) and the right lower chamber (ventricle) — is malformed and often leaks.

Combination of congenital heart defects

Some infants are born with several heart defects that affect the structure and function of the heart. Very complex heart problems may cause significant changes in blood flow or undeveloped heart chambers.

For example, tetralogy of Fallot (teh-TRAL-uh-jee of fuh-LOW) is a combination of four defects:

• A hole in the wall between the heart's ventricles
• A narrowed passage between the right ventricle and pulmonary artery
• A shift in the connection of the aorta to the heart
• Thickened muscle in the right ventricle

Other examples of complex congenital heart defects are:

• Pulmonary atresia. The pulmonary valve is missing, causing abnormal blood flow to the lungs.
• Tricuspid atresia. The tricuspid valve isn't formed. Instead, there's solid tissue between the right upper heart chamber (atrium) and the right lower chamber (ventricle). This congenital heart defect restricts blood flow and causes the right ventricle to be underdeveloped.
• Transposition of the great arteries. In this serious, rare heart defect, the two main arteries leaving the heart are reversed (transposed). There are two types. Complete transposition of the great arteries is typically noticed during pregnancy or soon after birth. Levo-transposition of the great arteries (L-TGA) is less common, and symptoms may not be noticed right away.
• Hypoplastic left heart syndrome. A major part of the heart fails to develop properly. For example, in hypoplastic left heart syndrome, the left side of the heart hasn't developed enough to effectively pump enough blood to the body.