It always indicates that rapid flow is present. Intrastenosis PSV divided by distal aortic PSV 7. The waveform distal to a hemodynamically significant lesion is often a low-resistance waveform. The waveform distal to a hemodynamically significant lesion often demonstrates abnormally high resistance. The waveform proximal to a hemodynamically significant lesion may demonstrate abnormally high resistance.
Inappropriate technique can yield a spurious diagnosis of occlusion.
The criterion is absence of detectable flow. Very slow flow can result in a false-positive finding. The normal ABI is greater than 1.0. A decrease in systolic pressure in the leg relative to the arm indicates the presence of an intervening obstructive lesion. The ABI correlates with the severity and nature of symptoms.