Variability of carotid bruit spectral analysis.

The reproducibility of determination of stenosis of the carotid artery by bruit spectral analysis was studied in 20 patients with 29 cervical bruits. The tests were performed with the Spectraview, a dedicated microcomputer which performs the analysis by the method of Lees. The estimated residual lumen was calculated from the break frequency of the power spectrum at peak systole. Each patient was studied on five separate occasions during a week. The lowest day-to-day variation was found with those lesions with the smallest residual lumen diameter. Six patients with wide ranges had major swings of blood pressure or pulse. When the bruit analysis results from days with similar blood pressure and pulse were compared, there was a low variability. The lesser stenoses had a wider spread of break frequency, but in this range, the variation represented only small differences in lumen diameter. The results of this study indicate that bruit spectral analysis can estimate the residual lumen diameter with an acceptable day-to-day variation.