Ventricular septal defect (VSD) is best described as which of the following?

• A. Acyanotic defect involving a hole in the septum between the atria
• B. Cyanotic defect with a hole between the ventricles
• C. Defect with an opening in the ventricular outflow tract
• D. An acyanotic defect with an opening in the septum between the right and left ventricles

Answer: (D)

Ventricular septal defect is about a hole in the interventricular septum, allowing communication between the left and right ventricles. Because the left ventricle operates at higher pressure, blood tends to flow from the left ventricle into the right ventricle and then to the lungs. This increases pulmonary blood flow but keeps the oxygen content of systemic blood normal, so it’s described as acyanotic. The opening is specifically between the right and left ventricles, not between the atria, and it isn’t an opening in the ventricular outflow tract. (Only with very large shunts and long-standing pulmonary hypertension can cyanosis develop later, but the typical description remains acyanotic.)