Objective criteria for the interpretation of carotid artery spectral analysis patterns.

The duplex scanner (imager + pulsed Doppler) in combination with a fast Fourier transform spectrum analyzer has been used to identify areas of arterial narrowing. To evaluate its effectiveness in the detection of clinically significant carotid stenosis, 1 previously described and 2 original objective parameters were applied to the real time sound frequency tracings from 157 carotid arteries that also had angiograms available to determine the presence and degree of stenotic involvement. There was a statistically significant difference between the means of the test scores of the group of vessels with high grade narrowing (greater than or equal to 60%) and those with less than 40% stenosis for all 3 criteria. Of major clinical interest were our 2 parameters, the 3-point diastolic internal carotid frequency total and the internal-to-common carotid spectral area ratio, both of which showed considerable promise as predictors of stenotic disease. For each test, 40/46 (87%) of the test scores of the arteries with 50% or greater narrowing fell outside 2 standard deviations (95% confidence level) of the means of the vessels with less than 50% stenosis. A previously reported parameter, the internal-to-common carotid peak systolic frequency ratio, was notably less discriminant in this regard.