Analysis and comparison of pressure gradients and ratios for predicting iliac stenosis.

Over the past 35 years five different pressure variables and their numeric criteria have been recommended to determine the hemodynamic significance of iliac artery stenosis. To analyze and compare the five variables, systolic and mean radial and femoral artery pressures were measured intraoperatively in 144 legs at rest and in 119 (83%) of these during hyperemic flow augmentation with papaverine. Iliac artery diameter stenosis measured from preoperative two-view arteriograms was 48 +/- 37% (mean +/- 1 SD). Resting systolic and resting mean pressure gradients (radial minus femoral artery pressure), hyperemic mean pressure gradients, hyperemic systolic pressure ratios (femoral/radial), and the percentage change from rest to hyperemia of the systolic pressure ratios were measured. For completeness a sixth variable, the hyperemic systolic pressure gradient, was also measured. High-grade (75%) stenosis is predicted with 95% confidence by resting pressure gradients > or = 52 mm Hg systolic and > or = 16 mm Hg mean and resting systolic pressure ratios < or = 0.61. Hyperemia is unnecessary and not useful for predicting > 50% stenosis. The rest-to-hyperemia percentage changes in systolic pressure ratios give poor results. Moderate (50%) stenosis is predicted with 95% confidence by resting pressure gradients > or = 34 mm Hg systolic and > or = 7 mm Hg mean, hyperemic mean pressure gradients > or = 30 mm Hg, and systolic pressure ratios < or = 0.73. Most published criteria have low accuracy, low predictive value, and a low optimal percentage of stenosis range. Simple pressure gradients give optimal results.