A person with a ventricular septal defect has a hole in the ventricular septum, which separates the right ventricle from the left ventricle in the heart.

The ventricular septum is the wall that separates the lower chambers of the heart, called the ventricles. A ventricular septal defect creates a disturbance in blood flow through the heart. Such a defect allows blood to flow from the left ventricle to the right ventricle. This can damage the right ventricle and the lungs.