The atrial septal defects constitute a common variety of CHD. Incidence of ASD has been reported to be 6/1000 live births. Females are more frequently affected than males. Atrial septal defect has been found to be associated with most of the autosomal and sex chromosome aberrations and is a common accompaniment of trisomies including trisomy 18 and trisomy 21.
There are three clinically significant types of atrial septal defects:
i) Osteum secundum defect.
ii) Endocardia! cushion defect
with osteum primum defect.
iii) Complete failure of formation
of interatrial septum leading to a