A 41-year-old asymptomatic male was referred to our cardiology outpatient clinic for diagnostic evaluation of a suspected bicuspid aortic valve at transthoracic echocardiography. Trans-oesophageal imaging ruled-out the bicuspid aortic valve, but detected an accessory membrane lining the interatrial septum with a double-layered appearance encompassing most of the fossa ovalis. Agitated saline infusion demonstrated an inter-atrial communication with right-to-left shunt under Valsalva manoeuvre. Cardiovascular magnetic resonance cine imaging confirmed the presence of a double interatrial septum featuring a midline recess enclosed by the two septa. Under end-expiratory breath-holding conditions, a transient right-to-left shunt was observed confirming the echocardiographic evaluation (Panel 1). No history of cerebrovascular disease and no clinical or imaging findings of right heart overload were registered.
Double interatrial septum is a rare congenital condition, by morphological side, allegedly associated with an increased risk of left-sided embolic events due to blood stasis within the accessory interatrial chamber, that is often found in continuity with both atria through patent foramen ovale or additional septal fenestrations. In this case, multimodality imaging effectively was able to detect the presence of this rare atrial septal abnormality and to distinguish that from others alterations of the interatrial septum shown in the table below (Table 1). Nevertheless, the clinical significance of double interatrial septum remains uncertain, no clear relationship with embolic stroke is known and no recommendation can be made regarding the decision-making for long-term anti-thrombotic management. High quality evidences are needed to evaluate whether double atrial septum or other atrial septal abnormalities might be considered as actionable risk factors of ischemic stroke or not.