Atrial Septal Defect

In a heart with an Atrial Septal Defect (ASD) there is communication between the right and left atria which causes a left to right shunting of blood due to the lower pressure in the pulmonary circulatory system. Consequently there is a mixing of oxygenated (systemic) and deoxygenated (pulmonary) blood.

There are two types of ASD:

• Primum type involves the endocardial cushions.
• Secundum type involves septum primum or septum secundum.