Eisenmenger’s syndrome occurs before the age of 1 year in children with very high pulmonary blood flow, such as unrepaired AVSD, but may occur at the age of 40-50 years in adults with unrepaired ASD who have had moderately increased pulmonary blood flow over many years. Corrective cardiac surgery to avoid Eisenmenger’s must be undertaken before the onset of pulmonary vascular disease, the ideal age dependent on the severity of the underlying lesion.