In which of the following conditions left atrium is not enlarged?

ASD is associated with an enlarged right atrium and right ventricle to accommodate large volume of blood. The left atrium is not enlarged because it decompresses itself by shunting blood to the right atrium at a minor difference in pressure. The left atrium may enlarge once Eissenmenger's syndrome develops and a reversal of shunt is seen across the defect. Ref: Essential Pediatrics, 6th Edition By O P Ghai, Pages 400-1.