Ventricular septal defect
A ventricular septal defect (VSD) is a hole in the ventricular septum, the wall dividing the left and right ventricles of the heart. It is a common congenital heart defect, although restrictive muscular VSDs are not true pathological defects; they are typically just a delayed closure of the ventricular septum.
Source: Wikipedia — Ventricular septal defect (CC BY-SA 4.0)