The ostium primum atrial septal defect is a defect in the atrial septum at the level of the tricuspid and mitral valves.
[en.wikipedia.org]
Ostium primum atrial septal defect Schemating drawing showing the location of different types of ASD, the view is into an opened right atrium.
[ipfs.io]
Defects, Atrial, ATRIAL SEPTAL DEFECT, Defect, Atrial Septal, Defects, Atrial Septal, HEART SEPTAL DEFECT ATRIAL, IA SEPTAL DEFECT, SEPTAL DEFECT INTERATRIAL, Septal Defect
[fpnotebook.com]