Explain about Atrial Septal Defect (ASD) ?

ASD occurs as an isolated anomaly in 5- 10 per cent of all CHDs. These communications occur in four sites i.e. in the central portion of atrial septum, in the position of foramen termed fossa ovalis or secundum defects. In the region of SVC - right atrium junction termed sinus venosus defects. Defect created by failure to seal the septum premium, called ostiurn primum defect. An unroofed coronary sinus is a rare communication between the coronary sinus and the left atrium.

Figure: Atrial septal defect