Limitations of the femoral artery pulsatility index with aortoiliac artery stenosis: an experimental study.

Relationships between femoral artery pulsatility index (PI) (a number calculated from Doppler-derived arterial blood velocity waveforms) and three directly measured physiologic parameters (proximal artery stenosis, blood pressure index (BPI), and blood flow) were studied in a canine model. All combinations of stenoses were constructed, including 0%, 25%, 50%, 75%, and 90% reduction in a cross-sectional area in the infrarenal aorta and/or left common iliac artery of 14 animals. PIs, BPIs, and mean blood flows were measured for each stenosis pattern at both the right (control) and left femoral arteries. Three groups were studied--group I, the left femoral artery remained open; group II, the left femoral artery was ligated; and group III, a left femoral arteriovenous fistula was constructed. Correlations between reductions in femoral artery PI and increasing arterial stenosis as well as decreasing BPI and blood flow were obtained. However, positive correlations were weak and only recognized when high-grade stenoses were present. Moreover, these correlations were further influenced by the multiplicity of stenoses present as well as flow velocity into the distal arterial bed. These data suggest that PI lacks the sensitivity to be a clinically useful diagnostic test.