Large VSDs allow blood to flow from the left ventricle to the right ventricle and lead to increase in pressure and flow in the lung circulation. This places significant strain on the heart and affected babies usually need surgical repair of the defect.

The effects of high flow and pressure in the lung circulation lead to breathlessness, poor feeding and slow weight gain in most affected babies. Early repair is usually recommended if the pressure in the lungs is markedly elevated. Some defects may gradually diminish in size and the effects on the heart may become less severe, allowing surgery to be delayed until later or avoided
altogether.

The position of the VSD in the partition between the ventricles varies from one patient to another. Sometimes there are multiple defects. Surgical repair is often required in the first three to six months. The defect is closed with a patch made from artificial material (e.g. Dacron). Sometimes surgery is required later on, even if the defect is smaller, because of the development of secondary problems - such as damage to one of the heart valves.

In suitable cases, in larger children, device closure may be feasible.