Abstract 14201: Double the Trouble: Extremely Rare Incidental Finding of a Double Interatrial Septum With Atrial Septal Aneurysm and Coexisting Patent Foramen Ovale

Abstract

Case: A 59-year-old female with a past medical history of hypothyroidism and IgG deficiency presents to cardiology clinic due to palpitations and premature ventricular complexes (PVCs) noted at a recent urgent care visit. In-office vitals, physical exam, labs, and EKG were unremarkable. Ambulatory cardiac monitoring showed predominantly sinus rhythm with a PVC burden of 1.4%. Echocardiogram revealed an extremely rare structural anomaly – a double interatrial septum (DIAS) with atrial septal aneurysm. Cardiac MRI (cMRI) further confirmed the presence of a DIAS enclosing an interatrial space, along with blood flow within the interatrial space and a discontinuity in the anterior right lateral atrial septum suggestive of a patent foramen ovale (PFO). There was no evidence of thrombus within the interatrial or intracardiac spaces. Mild right atrial enlargement was seen. The patient was initiated on aspirin for cardioembolic stroke prophylaxis. Discussion: DIAS is a highly rare congenital cardiac anomaly with limited number of cases in literature. It has been described as a midline third atrium resulting in a “tri-atrial heart”. As of 2018, less than 20 cases have been cited. DIAS is characterized by two parallel interatrial septa along with a clear echo lucent midline space that expands in systole and collapses in diastole. This case is unique as it is one of the few to include additional characterization with cMRI. Patients with DIAS are usually asymptomatic but can experience cardioembolic events as the interatrial space is at risk for thrombus formation. Communication across the DIAS makes these events more likely. Unlike with atrial fibrillation/flutter, no current criteria for anticoagulation (AC) initiation exists for DIAS given the scarcity of cases. While some sources advocate for use of anti-platelet agents, others have indicated a preference for oral AC. Our patient had an interatrial space and a PFO but lacked communication across the DIAS, had low bleeding risk, and no other classic risk factors of Virchow’s triad. We determined her risk for thrombus formation to be relatively low, and thus initiated her on aspirin over oral AC. Percutaneous closure of the interatrial space was deferred as it has been dismissed as a viable treatment option in the literature.