Aortic isthmus flow reversal in fetal coarctation of the aorta and the associated factors.

Reversal of flow in the aortic isthmus is much more common in true-positive cases of CoA as compared to controls, and isthmic flow reversal in the full systolic phase only suggests presence of CoA. The aortic isthmic reversed flow volume accounts for over half of the isthmic forward flow volume in the CoA-positive fetuses than in the normal controls.