A ventricular septal defect (VSD), a hole in the heart, is a common heart defect that's present at birth (congenital). The hole occurs in the wall that separates the heart's lower chambers (septum) and allows blood to pass from the left to the right side of the heart. The oxygen-rich blood then gets pumped back to the lungs instead of out to the body, causing the heart to work harder.
A small ventricular septal defect may cause no problems, and many small VSDs close on their own. Larger VSDs need surgical repair early in life to prevent complications.