How does it affect the heart?
Normally, the left side of the heart only pumps blood to the body, and the heart's right side only pumps blood to the lungs. In a child with VSD, blood can travel across the hole from the left pumping chamber (left ventricle) to the right pumping chamber (right ventricle) and out into the lung arteries. If the VSD is large, the extra blood being pumped into the lung arteries makes the heart and lungs work harder and the lungs can become congested