Inter atrial septal aneurysm is a benign disorder of IAS where the flap of fossa ovalis bulges on either to right or left atrium. It may be associated with fine fenestration or even a classical ostium secundum ASD.
Though the pressure within the atria is one of the determinant of this bulge.The morphology of the flap is such that it more often prolapse into LA than RA. Rarely it can be dynamic and moves 180 degrees , buckling between RA and LA .This unusual motion is real stress to IAS and can trigger atrial ectopic beats. and atrial tachycardia .