In atrial septal defects, which location is most commonly involved?

In atrial septal defects, which location is most commonly involved?

• A. Sinus venosus
• B. Primum
• C. Secundum
• D. Coronary sinus

Answer: (C)

The main idea is that the location of an atrial septal defect reflects how the atrial septum develops. The most frequent defect sits in the central portion of the atrial septum, the region of the fossa ovalis, known as a secundum defect. This happens when the septum primum either resorbs too much or the septum secundum doesn’t grow enough, leaving a hole after birth. Other types occur less often: primum defects are lower in the septum near the AV valves and are often part of more complex cushion-related defects; sinus venosus defects are near where the vena cavae enter the heart and frequently come with abnormal pulmonary venous drainage; coronary sinus defects are rare and lie in the wall of the coronary sinus. So, the most common location is the central atrial septum at the fossa ovalis (secundum).

The main idea is that the location of an atrial septal defect reflects how the atrial septum develops. The most frequent defect sits in the central portion of the atrial septum, the region of the fossa ovalis, known as a secundum defect. This happens when the septum primum either resorbs too much or the septum secundum doesn’t grow enough, leaving a hole after birth. Other types occur less often: primum defects are lower in the septum near the AV valves and are often part of more complex cushion-related defects; sinus venosus defects are near where the vena cavae enter the heart and frequently come with abnormal pulmonary venous drainage; coronary sinus defects are rare and lie in the wall of the coronary sinus. So, the most common location is the central atrial septum at the fossa ovalis (secundum).