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.

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.)

• The ostium secundum atrial septal defect is the most common type of atrial septal defect.
• Accounts for 60%-70% of ASDs
• Comprises 6-10% of all congenital heart diseases.
• Arises from an enlarged foramen ovale, inadequate growth of the septum secundum, or excessive absorption of the septum * 10 to 20 %of individuals with ostium secundum ASDs also have mitral valve prolapse .
• 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.
• Symptoms are typically decreased exercise tolerance, easy fatigueability, palpitations, and syncope.
• Complications of an uncorrected secundum ASD include pulmonary hypertension, right-sided heart failure, atrial fibrillation or flutter, stroke, and Eisenmenger's syndrome.
• While pulmonary hypertension is unusual before 20 years of age, it is seen in 50% of individuals above the age of 40.
• 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.
• Progression to Eisenmenger's syndrome occurs in 5 to 10% of individuals late in the disease process.

The septum secundum, semilunar in shape, 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.