by EBSCO Medical Review Board
(Atrioventricular Canal Defect; Atrioventricular Septal Defect; Endocardial Cushion Defect; Ventricular Septal Defect)


Septal defects are problems with the structure of the inside of the heart at birth. The problems are on a wall that is between the two upper chambers of the heart called atria. There are also two lower chambers of the heart 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 right 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 left ventricle pushes the blood out to the rest of the body. The blood from the left side should not mix with blood from the right side.

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. The means that the heart and lungs have to work harder than they need to work. This can lead to heart failure.

There are three main types of septal defects:

  • Atrial septal defect (ASD)—a hole in the wall between the atria
  • Ventricular septal defect (VSD)—a hole in the wall between the ventricles
  • Atrioventricular septal defect (AVSD)—a mix of ASD, VSD, and problems with openings between chambers called valves
Ventricular Septal Defect
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The cause is not always known.

Risk Factors

Things that may raise the risk of these problems are:

  • Family history of birth defects of the heart
  • Exposure to a viral infection, drugs, or alcohol during pregnancy
  • Taking certain medicines during pregnancy, such as those used to treat seizure disorder
  • Genetic disorders, such as Down syndrome


Many people with ASD or VSD do not have symptoms. Large defects and AVSD may cause:

  • Shortness of breath
  • Getting tired easily
  • Poor growth


A septal defect may be found during a regular exam. The doctor may hear a heart murmur.

The heart may be tested. This can be done with:

Chest x-rays may be done to look at the heart and the structures around it.


Treatment depends on the type and size of the defect. Choices are:

  • Monitoring small ASDs and VSDs to see if they close on their own
  • Medicines to ease symptoms of heart failure
  • Surgery to repair a defect that is causing problems and has not closed on its own


There are no known guidelines to prevent this health problem. The risk may be lowered with proper prenatal care.


American Heart Association 

National Institute of Child Health and Human Development 


Canadian Cardiovascular Society 

The College of Family Physicians of Canada 


Atrial septal defects. EBSCO DynaMed website. Available at: Accessed December 18, 2020.

Congenital heart defects. American Heart Association website. Available at: Accessed December 18, 2020.

Spicer DE, Hsu HH, et al. Ventricular septal defect. Orphanet J Rare Dis 2014 Dec 19;9:144.

Ventricular septal defect. EBSCO DynaMed website. Available at: Accessed December 18, 2020.

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