Atrial septal defect ostium secundum

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Ostium Secundum Atrial Septal Defect
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Priyamvada Singh, M.B.B.S. [[2]]; Cafer Zorkun, M.D., Ph.D. [3]; Assistant Editor-In-Chief: Kristin Feeney, B.S. [[4]]

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.

Image showing ostium secundum atrial septal defect

Interior of dorsal half of heart of human embryo of about thirty-five days. (Septum secundum visible at center top.)

Same heart as above, opened on right side. (Septum secundum visible in dark area at center top.)

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 it fuses with the primary septum, and by this means the foramen ovale is closed, but sometimes the 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 individuals with an uncorrected secundum ASD don't have significant symptoms through early adulthood. About 70% develop symptoms by the time they are in their 40s.
• Many a times they 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.
• 10 to 20 %of individuals with ostium secundum ASDs also have mitral valve prolapse .
• It is the commonest type of atrial septal defect and accounts 60%-70% of all ASDs.
• It comprises 6-10% of all congenital heart diseases.