A rare case of inferior sinus venosus atrial septal defect and concomitant hypoplasia of the posterior mitral valve leaflet

Inferior sinus venosus atrial septal defect (SVASD) is the rarest form of the atrial septal defect (ASD) and can sometimes go unnoticed. Although this defect can be associated with other congenital anomalies, its association with hypoplasia of the posterior mitral leaflet is extremely rare. In this case, we present a woman with a history of surgery for an ostium secundum ASD who exhibited persistent right heart chamber dilation. Echocardiography revealed hypoplasia of the posterior mitral leaflet, and cardiac magnetic resonance (CMR) imaging confirmed the presence of a previously undetected inferior sinus venosus ASD.