Upstream stenosis. Its diagnosis by Doppler signals from the femoral artery.

Transcutaneous femoral artery Doppler signals were measured with a 10-MHz pencil probe in 263 lower limbs of 135 patients. The Doppler waveforms were compared with arteriograms in 125 limbs with lower-limb ischemia and in 138 controls in the detection of minor (< 50%) and major (> 50%) iliac-artery stenosis. Doppler maximum velocity-time waveforms were obtained using a maximum frequency follower, and the wave-form shape was analyzed using a Laplace transform (LT) to produce a coefficient, the LT damping. Pulsatility index (PI) was also calculated. In 62 limbs with minor artery disease, mean LT damping was significantly greater than normal (0.5 +/- 0.15 vs 0.33 +/- 0.06; P < .001). In 63 limbs with major iliac stenosis, mean LT damping was higher still (0.78 +/- 0.16; P < .02). The LT damping was not affected by increased distal impedance and there was a good correlation with iliac stenosis in 65 limbs with an occluded superficial femoral artery (r = -0.73). The results with PI were inferior at every grade of severity of iliac disease when assessed by receiver-operator characteristic curves. These results suggest that LT damping is a sensitive method of analyzing femoral Doppler signals in the noninvasive detection of iliac artery stenosis.