Atrioventricular septal defect (AVSD)

Atrioventricular septal defect (AVSD) is a heart condition that is present at birth. That means it's a congenital heart defect. Children born with this condition have a hole in the wall between the heart's chambers and changes to the mitral and tricuspid heart valves. 

Other names for this condition are:

• Atrioventricular canal defect.
• Endocardial cushion defect.

With atrioventricular septal defect, extra blood flows to the lungs. The extra blood forces the heart to work too hard.

For every 10,000 live births in the U.S., 3 or 4 babies are born with atrioventricular septal defect. If not treated, the condition can cause high blood pressure in the lungs and heart failure. Treatment may involve surgery early in life to close the hole in the heart and to repair the valves.

Types of atrioventricular septal defect include:

• Complete AVSD. This causes a hole between the right and left sides of the heart and between the upper and lower chambers. The upper chambers are called the atria. The lower chambers are called the ventricles. Complete AVSD affects all four chambers.
  
  Complete AVSD also affects the heart valves. The tricuspid and mitral valves form as one common valve. As a result, the valve may not close fully, causing blood to flow back into the chambers.
  
  A complete AVSD may be balanced or unbalanced. In a balanced AVSD, the left and right ventricles are big enough and close enough in size. Unbalanced means that one ventricle is less developed than the other.
• Partial or incomplete AVSD. This causes a hole only in the upper chambers of the heart. It also involves the heart valves. The mitral and tricuspid valves are separate, but they do not form typically. The mitral valve may have an opening, called a cleft, that can allow blood to leak backward.
• Transitional AVSD. This type involves a large hole in the upper heart chambers and a smaller hole in the lower chambers. The large hole lets extra blood flow into the lungs. The heart valves do not form typically.

Atrioventricular septal defect symptoms depend on whether the defect is partial or complete.

Complete AVSD

The condition affects all four heart chambers. Symptoms of a complete atrioventricular septal defect most often happen within a few months after birth. Typically, symptoms are like those of heart failure. They may include:

• Trouble breathing or fast breathing.
• Heavy sweating, especially when feeding.
• Tiredness.
• Trouble feeding.
• Poor weight gain.
• Wheezing.

Partial AVSD

The condition affects only the two upper heart chambers. Symptoms of a partial atrioventricular septal defect may not appear until late childhood or early adulthood. The symptoms may be due to complications such as heart valve disease, high blood pressure in the lungs or heart failure. Symptoms may include:

• Tiredness and weakness.
• Fast or irregular heartbeat, also called an arrhythmia.
• Not being able to exercise as much.
• Shortness of breath.
• Swelling in the legs, ankles and feet.

 

 

Atrioventricular septal defect, also called atrioventricular canal defect, happens before birth when a baby's heart is forming. Experts aren't sure of the exact cause. But atrioventricular septal defect is linked with some genetic syndromes, such as Down syndrome, also called trisomy 21.

How the heart works

To understand congenital heart defects, it may help to know how the heart works.

The heart is divided into four chambers.

• The two upper chambers are called the atria.
• The two lower chambers are called the ventricles.

The right side of the heart moves blood into vessels that lead to the lungs, where the blood receives oxygen. The oxygen-rich blood flows back to the heart's left side and into the body's main artery, called the aorta. From there, the blood flows to the rest of the body.

Valves control blood flow into and out of the heart chambers. These heart valves open to let blood in. They close to keep blood from flowing backward.

What happens in atrioventricular septal defect

In a partial atrioventricular septal defect:

• There's a hole in the heart's wall between the upper chambers.
• The valve between the left chambers, called the mitral valve, has an unusual opening. The opening is called a cleft.
• Blood can leak backward through the opening.

In a complete atrioventricular septal defect:

• There's a large hole in the center of the heart. The hole is where the walls between the upper and the lower chambers meet.
• Oxygen-rich and oxygen-poor blood mix through the hole.
• There's one large valve between the heart's upper and lower chambers, instead of the typical separate valves.
• The heart must work harder to pump blood. The heart becomes larger.

There's a strong link between Down syndrome, also called trisomy 21, and atrioventricular septal defect. If prenatal testing detects AVSD, the baby has higher risk of having Down syndrome. A baby with Down syndrome has a higher risk of having an AVSD.

Possible complications of atrioventricular septal defect include:

• Enlarged heart. More blood flow through the heart forces it to work harder than usual. This can make it larger.
• High blood pressure in the lungs. This condition also is called pulmonary hypertension. A hole in the heart lets oxygen-rich blood mix with oxygen-poor blood. The lungs get too much blood. Pressure builds up in the lungs.
• Heart failure. If atrioventricular septal defect is not treated, the heart can't pump enough blood to meet the body's needs.

Pregnancy

Many people who have atrioventricular septal defect surgery can have a pregnancy. But they should see a doctor trained in congenital heart disease. This type of doctor is called an adult congenital cardiologist. Together you can discuss and plan for any special care needed during pregnancy.

There is no known prevention for atrioventricular septal defect.

Some heart conditions are passed down in families, which means they are inherited. If you have a family or personal history of congenital heart defects, talk with a genetic counselor and a heart doctor before you get pregnant.