PAEA Pediatrics End of Rotation (EOR) Practice Exam

The ostium secundum is the most common location for atrial septal defects (ASDs). This type of defect occurs in the middle portion of the atrial septum and is characterized by an opening that allows blood to flow from the left atrium to the right atrium, leading to increased volume in the right atrium and right ventricle.

The ostium secundum ASD is often related to an inadequate formation of the septum primum and septum secundum during embryonic development, which results in a persistent communication between the two atria. This defect can lead to right heart volume overload and, if left untreated, may result in complications such as pulmonary hypertension or atrial arrhythmias.

Other types of ASDs, like those located in the ostium primum and sinus venosus, are less common. The ventricular septum, while a location for a different type of congenital heart defect, does not pertain to atrial septal defects. Thus, the ostium secundum accounts for the majority of cases, describing the most prevalent anatomical site where these defects occur.