Background: Determination of the ankle-arm-index (AAI) by Doppler ultrasound is the method of choice as a screening test for peripheral arterial occlusive disease (PAOD). The easily performed Impedance Rheography (IR) may serve as an alternative screening method. This study investigates the correlations between parameters obtained by IR curve to the AAI.
Methods: 56 patients (62.8 +/- 13 years, m = 37, f = 19) were included in the study. IR was performed on both shanks using ring electrodes below the knee and above the ankle (bipolar leads, frequency 90 kHz, test voltage 2.5 Vpp). The AAI was obtained by a 8 Mz ultrasound probe.
Results: AAI < or = 0.85 showed significant correlations (p < 0.0001) to parameters of the IR curve: Crest Time (GZ, r = 0.67), Rise of the Pulse Wave (PA, r = 0.82), Relative Pulse Volume (RP, r = 0.82) and the Rheographic Quotient (RQ, r = 0.86). AAI > 0.85 showed no or only weak correlations to RI parameters. Underlying the following limits for rheographic parameters (GZ = 159 ms, PA = 3.3, RP = 0.43 vp/s and RQ = 0.4 vp), sensitivity and specify was determined: GZ: 68% and 100%, PA: 84% and 88%, RP: 68% and 92%, RQ: 77% and 88%.
Conclusions: Impedance rheography correlates significantly with the AAI. Therefore this method seems to be well suited as a screening test for PAOD.