Atrial septal defect (ASD) flow jets visualize in the subcostal and the right parasternal views, and sometimes from the apical four-chamber view. ASDs are usually associated with low velocity blood flow that is continuous throughout the cardiac cycle, but is most prominent during late systole and early diastole. Blood flow through an ASD typically moves from left to right, but can move from right to left or bidirectional, depending on the LA pressures.

An ASD flow jet seen in this subcostal view, frozen in early diastole. A variance map is used. Since this ASD flow jet moves toward the transducer, it is primarily red with a central jet of aliased blue. The yellows and greens in the jet represent highly turbulent blood flow.