Atrial septal defect overview
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
Atrial septal defects (ASD) are a group of congenital heart diseases that involve the inter-atrial septum. The inter-atrial septum is the tissue that separates the right and left atria from each other. This tissue prevents arterial and venous blood from mixing with each other. If there is a defect in this septum, a direct communication between the atria can occur, which allows shunting, resulting in mixing of arterial and venous blood. It is possible for blood to travel from the left side of the heart to the right side of the heart, or vice versa. The direction of shunting will depend on a variety of factors, notable the patient's hemodynamics.
It should be noted however, that a "Right-to-left-shunt" typically poses the more dangerous scenario (See Pathophysiology below). Since the right side of the heart contains venous blood with a low oxygen content, and the left side of the heart contains arterial blood with a high oxygen content, right to left shunts can cause hypoxia and result in cyanosis. Additionally, a communication between the two atria may allow blood clots to pass from the venous system to the arterial system and result in a stroke or peripheral embolism.