Septal defects are problems with the structure of the heart. They are present at birth. Septal defects are located on the inside of the heart. They are on a wall that separates the chambers of the heart. There are two upper chambers of the heart called atrium. Two lower chambers of the heart are called ventricles.

In a healthy heart, the blood flows from the body to the right atrium. The blood then goes into the right ventricle. The ventricle pumps this blood to the lungs to pick up fresh oxygen. The blood then returns to the left side of the heart. It enters the left atrium first, then down to the left ventricle. The ventricle pushes the blood out to the rest of the body.

Septal defects allow the blood to move between the left and right chambers. The blood most often moves from the left side of the heart into the right side. This means that blood that has just returned from the lungs may end up being sent right back to the lungs. As a result, both the heart and lungs have to work harder than they need to work.

There are three main types of septal defects:

  • Atrial septal defect (ASD)—a hole in the wall between the two upper chambers (atrium) of the heart
  • Ventricular septal defect (VSD)—a hole in the wall between the two lower chambers (ventricles) of the heart
  • Atrioventricular septal defect (AVSD)—a combination of ASD, VSD, and problems with opening between chambers called valves

The stress of pushing extra blood to the lungs may lead to heart failure. The following information applies to all three of these defects except where noted.

Ventricular Septal Defect
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In most cases the cause is not known.