This is a relatively common abnormality of IAS. It is often observed as IAS bulging into left or right atrium in routine echocardiogram.If this happens without atrial hypertension it is termed as IAS aneurysm .
This is due to valve of foramen ovale bending into the RA/LA* cavity for various distance. By definition , the radius of curvature of the bulge should be more than 10 mm to label it as IAS aneurysm.
*Bulging into RA more common
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- Mostly a benign entity.
- More often observed in association with PFOs or ostium secundum ASD.
- When occurs in isolation does not result in any shunting across it
- The septal bulge can be static or dynamic . It could swing into LA, RA, and back to LA or vice versa.
- Anatomically 5 types are proposed.
- Multiple fenestration in the aneurysms have been noted.
- Aneurysm formation may aid in spontaneous closure of ASD.
- IAS aneurysm tend to aggravate stasis of LA blood flow and predispose to minute LA clots and systemic thrombo embolism .
- IAS aneurysm can act as an arrhythmic focus , generating focal atrial tachycardias.
- A non ejection click may be occasionally heard as the IAS aneurysm bulges and tenses within LA/RA cavity .
1 . Olivares -Reyes A, et al. Atrial Septal Aneurysm: A new classification in 205 adults. J Am Soc Echocardiogr
2. Longhini C, et al. Atrial septal aneurysm: echocardiographic study. Am J Cardiol 1985;56:653-67.
3. Gondi B, Nanda NC. Two-dimensional echocardiographic features of atrial septal aneurysm. Circulation 1981;63:452-57