Unroofed coronary sinus = Coronary sinus type ASD

Unroofed coronary sinus is a rare type of ASD.
The defect is inferior and slightly anterior to the fossa ovalis, at the expected site of the coronary sinus ostium.
Part or all of the common wall between coronary sinus and left atrium is absent.
It is often associated with a persistent left SVC that joins the roof of the left atrium