**5.2 Progression to pulmonary vascular obstructive disease**

PVOD may develop in 10% of untreated VSDs. This is likely to be due to the exposure of the pulmonary vascular bed to high flow and high pressure. Speedy diagnosis and closure of the VSD at least prior to 18 months of age is expected to decrease the incidence of development of PVOD.

With the advent of better echocardiographic imaging as well as its availability, the incidence of Eisenmenger's syndrome and irreversible PVOD has decreased but still exists in less than 10% of patients. Such patients are often are diagnosed in adulthood, particularly in developing countries. In many of these patients, prognosis maybe worse after surgical repair. In a subset of patients with VSD and PAH, newer treatment modalities such as pulmonary vasodilators have made some patients amenable to repair. However, immediate post-operative survival does not necessarily assure good long-term outcomes [17].
