Embryological Basis of Congenital Cardiac and Tracheoesophageal Defects

Formation of the Atrial Septum

The atrial septum develops from complex interactions between embryonic tissues, beginning with the septum primum and septum secundum. Any disruptions in this process can lead to atrial septal defects (ASDs), characterized by abnormal communication between the left and right atria.

Mechanisms Leading to Atrial Septal Defect

• Failure of septum primum fusion: If the septum primum does not fully close, a persistent ostium secundum defect may result.
• Malformation of the septum secundum: Inadequate development of the septum secundum can leave a patent foramen ovale.
• Abnormal apoptosis: Excessive programmed cell death may disrupt the balance of septal formation.

Understanding these embryological mechanisms is critical for diagnosing and managing congenital cardiac defects.