Ostium primum type ASD is associated with which developmental process failure?

Ostium primum type ASD is associated with which developmental process failure?

• A. Neural crest cell migration
• B. Endocardial cushion formation
• C. Down syndrome
• D. No associations

Answer: (A)

Ostium primum ASD arises from a failure in the formation and fusion of the endocardial cushions, which are essential structures that help form the lower part of the atrial septum and the atrioventricular (AV) valves. When these cushions don’t develop properly or fail to fuse with the septum primum, a defect remains at the ostium primum region, producing this type of atrial septal defect. This is why ostium primum ASD is classically linked with AV canal defects and is frequently seen in Down syndrome, where endocardial cushion defects are common. Neural crest cell migration, by contrast, is more closely associated with outflow tract and conotruncal development (such as defects like persistent truncus arteriosus or tetralogy of Fallot) rather than the ostium primum region of the atrial septum. So the key developmental failure for ostium primum ASD is endocardial cushion formation. This explains the strong association with Down syndrome and why defects in cushion formation are the underlying mechanism.

Ostium primum ASD arises from a failure in the formation and fusion of the endocardial cushions, which are essential structures that help form the lower part of the atrial septum and the atrioventricular (AV) valves. When these cushions don’t develop properly or fail to fuse with the septum primum, a defect remains at the ostium primum region, producing this type of atrial septal defect. This is why ostium primum ASD is classically linked with AV canal defects and is frequently seen in Down syndrome, where endocardial cushion defects are common.

Neural crest cell migration, by contrast, is more closely associated with outflow tract and conotruncal development (such as defects like persistent truncus arteriosus or tetralogy of Fallot) rather than the ostium primum region of the atrial septum. So the key developmental failure for ostium primum ASD is endocardial cushion formation. This explains the strong association with Down syndrome and why defects in cushion formation are the underlying mechanism.