Atrial septal defect (ASD)

View the Heart Disease Slideshow

Medical Definition of Atrial septal defect (ASD)

Atrial septal defect (ASD): A hole in the septum, the wall, between the atria, the upper chambers of the heart. Commonly called an ASD. ASDs constitute a major class of heart formation abnormalities present at birth (congenital cardiac malformations). Normally, when clots in veins break off, they travel first to the right side of the heart and, then to the lungs where they lodge as an obstruction (embolus). The lungs act as a filter to prevent the clots from entering the arterial circulation. However, when there is an ASD, a clot can cross from the right to the left side of the heart, then pass into the arteries as a paradoxical embolism. Once in the arterial circulation, a clot can travel to the brain, block a vessel there, and cause a stroke (cerebrovascular accident). Because of the risk of stroke from paradoxical embolism, it is usually recommended that even small ASDs be closed (repaired).


Quick GuideHeart Disease: Causes of a Heart Attack

Heart Disease: Causes of a Heart Attack

Subscribe to MedicineNet's Heart Health Newsletter

By clicking Submit, I agree to the MedicineNet's Terms & Conditions & Privacy Policy and understand that I may opt out of MedicineNet's subscriptions at any time.

Reviewed on 5/13/2016

Health Solutions From Our Sponsors