Spectrum of Interatrial Shunts Presenting with an Intact Atrial Septum: Imaging Features at Echocardiography, CT, and MRI.

Communication between the right atrium and left atrium in the presence of an intact interatrial septum is possible, although uncommon. This may occur in isolation or in association with other forms of congenital heart disease. Shunting may occur via unroofing (a deficiency in tissue, which could be due to a lack of formation or the regression of the vessel walls during embryologic development), via anomalous or decompressing veins, or from a combination of multiple anomalies. Surgical correction is typically necessary for patients, as there is a predisposition to develop cardiovascular and cerebrovascular events. Echocardiography, cardiac MRI, and CT enable the diagnosis of these shunts. It is crucial for imagers to understand the pathophysiology and identify any associated anomalies that may affect the interpretation, choice of intervention, and treatment outcome. The purpose of this review is to provide a comprehensive overview of interatrial communications with an intact atrial septum, including their embryology, pathophysiology, imaging features, and management strategies. Keywords: Congenital, Cardiac, CT, MR Imaging, Echocardiography, Interarterial Shunts, Intact Atrial Septum, Congenital Heart Disease, Unroofing Defects, Anomalous Veins © RSNA, 2025.