Summary

• A defect in the interventricular septum that allows shunting of blood between the left and right ventricles.
• Usually congenital, but rarely acquired after myocardial infarction or trauma.
• May be associated with other congenital defects such as tetralogy of Fallot.
• Significant left-to-right shunting results in pulmonary hypertension, which, if left untreated, can progress to shunt reversal with cyanosis and the Eisenmenger's syndrome.
• Small shunts may close spontaneously in childhood and can be managed by observation.
• Large shunts require surgical closure.