Atrial septal aneurysm as a potential source of neurological ischemic events.

An atrial septal aneurysm (ASA) is a congenital malformation of the atrial septum characterized by bulging of the septum overlying the fossa ovalis region into either atrium. The prevalence of ASA varies according to the diagnostic method used and to the type of population studied. A practical classification of ASA based on the current knowledge of its pathogenesis into Type I, Type II, and Type III is presented. With the widespread use of transesophageal echocardiography in recent years, ASA has become an increasingly recognized entity. Recently, the clinical interest in ASA has been increased by several reports in the literature proposing ASA as a potential source of emboli. The three most plausible mechanisms to link this association are thrombus formation in or around the ASA, paradoxical embolization through an interatrial communication in the form of patent foramen ovale or atrial septal defect, and mitral valve prolapse that has been found to be frequently associated with ASA. Although the echocardiographic detection of ASA is in most cases an incidental finding, the identification of ASA should prompt careful review of the echocardiogram for mitral valve prolapse, atrial septal defect, and patent foramen ovale. Although conclusive evidence of a causal relation between ASA and cerebrovascular emboli has not been shown, the identification of ASA in such patients in the absence of another cause to explain the embolic event may represent an indication for long-term antiplatelet or anticoagulation therapy, or even surgery. Until long-term follow-up results of these patients are available, management should be on an individual basis.