Fourier Analysis of Doppler Arterial Waveforms of Lower Extremity

Lee, Hong Gi; Yum, Myung Kul

Abstract

PURPOSE: Although it is well known that the pulsatile Doppler waveforms change in shape with disturbed flow, interpretation of the waveforms has largely been subjective. We aimed to describe the Doppler waveforms of the lower extremity objectively by parameters of Fourier transformation. METHOD: Sixty-eight Doppler arterial waves were analyzed in this study. They were classified according to the clinical findings; Group I: no ischemic symptoms with ankle pressure>100 mmHg (N=17). Group II: no ischemic symptoms with ankle pressure 80~100 mmHg (N=18). Group III:symptoms of claudication (N=19). Group IV: rest pain or tissue loss (N=14). The waveforms were Fourier transformed and their amplitudes and phases were compared up to the third harmonics. RESULT: Both the fundamental and second harmonics were predominant in group I. In contrast, fundamental harmonic was predominant with disturbed flow. The phases of the fundamental and second harmonics were delayed with disturbed flow. Relative phase (difference of phase between higher harmonics and fundamental harmonic) tended to be shortened with disturbed flow.
CONCLUSION
Abnormal waveforms are characterized by predominant amplitude of the first harmonic, phase delay, and shortening of the relative phase. These parameters may be useful for differentiation of Doppler waveforms.