Which cardiac defect is most commonly associated with Down syndrome?

Down syndrome, also known as Trisomy 21, is associated with several congenital heart defects, with endocardial cushion defects being the most common. Endocardial cushion defects are a type of atrioventricular septal defect (AVSD) that occurs when there is a failure of the embryonic structures to properly fuse, resulting in an incomplete separation of the chambers of the heart.

These defects often involve a combination of atrial septal defects and ventricular septal defects, along with issues in the heart valves. Since children with Down syndrome frequently present with defects that affect the atrioventricular endocardial cushions, this condition is particularly prevalent among this population.

In contrast, while other defects such as atrial septal defects and coarctation of the aorta can occur in children with Down syndrome, they do not have the same level of association. Endocardial cushion defects represent a more typical presentation in this group, contributing to the heart-related challenges many with Down syndrome face.