what is atrial septal defect
Atrial septal defect (ASD) is a congenital heart defect in which blood flows between the atria (upper chambers) of the heart.Normally, the atria are separated by a dividing wall, the interatrial septum. sinus venosus ASD is a type of atrial septum defect in which the defect in the septum involves the venous inflow of either the superior vena cava or the inferior vena cava. A sinus venosus ASD that involves the superior vena cava makes up 2 to 3% of all interatrial communication.