Atrial septal defect ostium secundum anatomy


 * Associate Editors-In-Chief: Priyamvada Singh, M.B.B.S. [mailto:psingh@perfuse.org]; ; Assistant Editor-In-Chief: Kristin Feeney, B.S. [mailto:kfeeney@perfuse.org]

For a full discussion on ostium secundum defects click here.

Overview
During fetal development, the septal wall may fail to fuse causing an atrial septal defect to arise. An ostium secundum atrial septal defect is one such type of malformation arising from the irregular development of the foramen ovale, septum secundum or septum primum. It is the most common type of atrial septal defect.

Anatomy of an Ostium Secundum Defect




Ostium Secundum Atrial Septal Defect

 * The septum secundum is semilunar in shape. It grows downward from the upper wall of the atrium immediately to the right of the primary septum and foramen ovale. Shortly after birth the septum secundum fuses with the primary septum and through this means the foramen ovale is closed. Sometimes the septal fusion is incomplete and the upper part of the foramen remains patent.


 * The limbus fossae ovalis denotes the free margin of the septum secundum. The ostium secundum (or foramen secundum) is a foramen in the septum primum. It should not be confused with the foramen ovale, which is a foramen in the septum secundum. It can arises from an enlarged foramen ovale, inadequate growth of the septum secundum, or excessive absorption of the septum.


 * Most of the times ostium secundum ASDs occur sporadically. However, they have been found to occur with increased incidences in some genetic disorders like, the Holt-Oram (heart-hand) syndrome, Down syndrome, Noonan syndrome,Treacher Collins syndrome, and the thrombocytopenia-absent radii (TAR) syndrome.


 * Most individuals with an uncorrected secundum ASD are asymptomic or experience minimal symptoms through early adulthood.
 * About 70% of all ostium secundum ASD patients develop symptoms by the time they are in their 40s.


 * 10 to 20 %of individuals with ostium secundum ASDs also have mitral valve prolapse.


 * It is the most common type of atrial septal defect and accounts 60%-70% of all ASDs.


 * It comprises 6-10% of all congenital heart diseases.