Imaging the Adult With Secundum Atrial Septal Defect: A Practical Echocardiographic Approach From Diagnosis to Device Closure

BACKGROUND: Secundum atrial septal defect (ASD) is one of the most common congenital heart defects encountered in adults. Echocardiography plays a central role in diagnosis, assessment of haemodynamic significance, anatomical characterization, transcatheter closure planning, and follow-up. However, the frequently non-circular geometry of secundum ASD can make accurate anatomical assessment challenging, particularly with single-plane measurements. PURPOSE: This narrative review provides a practical echocardiographic approach to adult secundum ASD, emphasizing the complementary roles of transthoracic echocardiography (TTE), multiplanar two-dimensional transesophageal echocardiography (TEE), color Doppler, and three-dimensional (3D) TEE. CONTENT: TTE provides initial diagnosis and assessment of physiological consequences, including right-sided chamber remodeling, ventricular function, tricuspid regurgitation, and pulmonary pressure. Multiplanar 2D TEE enables systematic assessment of ASD size, morphology, and surrounding septal rims, while measurements obtained in different planes may reveal substantial differences and highlight the limitations of single-plane sizing. 3D TEE provides an en-face spatial representation of the interatrial septum and complements 2D measurements by defining defect geometry, rim relationships, and suitability for transcatheter closure. Haemodynamic assessment should integrate right ventricular volume overload, shunt magnitude, pulmonary vascular status, and left ventricular disease rather than defect diameter alone. Cardiovascular magnetic resonance or cardiac computed tomography may provide complementary information when echocardiography is insufficient to define pulmonary venous connections, anatomy, or haemodynamics. CONCLUSION: A systematic multimodality echocardiographic approach integrates anatomical and physiological information throughout the management of adult secundum ASD. Combining TTE, multiplanar 2D TEE, 3D TEE, and targeted advanced imaging can facilitate individualized assessment and informed transcatheter closure planning.