Atrial Septal Aneurysm
The normal anatomic relationship between the aorta, superior caval vein and the oval fossa is illustrated here. The above 3D image of the atrial septum is visualized both from the left and right atrium by rotating the image. The persistant opening between the two atrial chambers (PFO) is often a slit like gap seen in the antero-cephalad aspect of the oval fossa. The cartoon below illustrates the corresponding long axis (B) and short axis (A) views. Please note that the PFO is drawn as an overlaping gap in the long axis plane. Compare this with the further illustrations given below.
Cartoon below illustrates the aneurismal atrial septum and its appearence in 3D and 2D long axis views. If there is significant overlap between the secondum and primum septae, then it forms a "tunnel" like PFO. If there is no overlap, it becomes an ASD of the secondum type.
Any degree of deviation or bulge in the atrial septum in the plane of the atrial septum, along an imaginary line running parallel to the superior and inferior caval veins, depicts an atrial septal aneurysm. Depending on the thickness and muscularization of the septa, the echogenicity of the aneurysm markedly varies . Colour Doppler interogation of the aneurysm is mandatory to differentiate between an aneurysmal atrial septum with fenestrations or an aneurysmal atrial septal defect (illustrated below).
Rarely, there may be mal-alignment between the planes of the secondum and primum septae. This is often associated with an aneurysmal ASD. Failure to recognize the degree of mal-alignment may lead to placement of the ASD/PFO device either to the left or right atrial aspect of the septum leading to device embolization. 3D visualization of the atrial septum especially in aneurysmal or malaligned septal defects helps to avoid complications and accurate placement of ASD device in multifenestrated defects.
The illustration below and the 3D image above shows a malaligned aneurysmal ASD. The device below is sitting on the atrial septum visualized from the LA aspect. It is only attached to the primum septum and jutts into the LA above the aneurysm.
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