USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

Where is the most common location for a Ventricular Septal Defect to occur?

1. In the muscular septum

2. In the membranous septum

3. At the apex of the heart

4. Between the atria

The correct answer is: In the membranous septum

The most common location for a Ventricular Septal Defect (VSD) to occur is in the membranous septum. This area, located along the outflow tract of the right ventricle, is a common site for defects due to its thin structure compared to the muscular septum. The membranous septum comprises a small area of fibrous tissue that can result in defects during embryonic development, leading to a more frequent occurrence of VSDs at this site. Ventricular septal defects can cause significant hemodynamic changes because they allow for left-to-right shunting of blood, leading to increased pulmonary blood flow. This situation is particularly relevant for defects that are located in the membranous septum, as they can lead to more pronounced clinical symptoms. Understanding the location facilitates diagnosis and management strategies for patients with congenital heart defects, particularly when planning for surgical intervention or monitoring for potential complications.