Analysis of femoral artery Doppler signals by LaPlace transform damping method.

The LaPlace transform damping (LTD) method of common femoral artery Doppler waveform analysis is a new method for assessing aortoiliac stenosis. A microcomputer was used to analyze the waveform to determine the value of the damping parameter, which is related to inflow stenosis. The study included 60 limbs with arterial disease and 20 limbs in normal control subjects. With a damping value of 0.60 used as the cutoff point between nonocclusive lesions and iliac stenoses of greater than 50% diameter reduction, we found a sensitivity of 100% and a specificity of 93% (overall accuracy 95%). Unlike Doppler waveform analysis by the pulsatility index method, the accuracy of the LTD method is not affected by occlusion of the superficial femoral artery. The Doppler signal processor and the computer currently used for the LTD analysis are simple to operate and fully suitable for routine use in a clinical vascular laboratory. Our experience indicates that the LTD method of waveform analysis provides the best noninvasive method for detection of significant inflow disease.