A neonate is found to have a persistent communication between the right and left atria after birth. If it is an ostium primum defect, which structure failed to develop correctly?

• A Endocardial cushions (atrioventricular cushions) failed to fuse with the septum primum ✓
• B Septum secundum failed to grow from the roof of the common atrium
• C Foramen ovale failed to close after birth
• D Septum primum failed to develop an ostium secundum

Explanation

Ostium primum ASD results from failure of the endocardial cushions (atrioventricular cushions) to fuse with the inferior edge of the septum primum before the ostium primum closes. This type of ASD is located at the lower part of the interatrial septum, close to the atrioventricular valves, and is associated with cleft mitral valve. Ostium secundum ASD results from excessive resorption of the septum primum or inadequate development of the septum secundum, leaving a central hole. Patent foramen ovale is a postnatal communication between the two septa.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.