SUMMARY The peak Doppler-shifted frequency and degree of lumen narrowing were compared in 75 cervical carotid stenoses. Peak frequency was not found to precisely indicate severity of stenosis, but it was possible to divide stenoses into four ranges of severity on the basis of peak frequency. Peak frequencies of less than 5 KHz, in most instances, indicated stenoses of less than 50% decrease in lumen area. Frequencies from 5 to 8 KHz were generally associated with stenoses of 50-75% decrease in lumen area, and frequencies of 8-12 KHz were most often associated with stenoses of 75-90% decrease in area. Frequencies greater than 12 KHz almost invariably occurred in very severe lesions of greater than 90% decrease in lumen area (> 70% decrease in diameter). The use of peak frequency as an indicator of severity of stenosis, while not specific, is felt to be of considerable clinical benefit as it provides a more quantitative evaluation of stenosis than auditory assessment of Doppler frequencies. Stroke, Vol 13, No 3, 1982 DOPPLER SONOGRAPHY has become an accepted method for clinical detection and evaluation of cervical carotid occlusive disease. One of the most important parameters used in Doppler assessment of carotid stenosis is the peak Doppler shift frequency occurring during systole.* Relatively little data is available, however, to indicate how precisely peak systolic frequency correlates with luminal narrowing and how peak systolic frequency measurements made with frequency spectrum analysis should be used in clinically gauging stenotic lesions. Spencer and Reid,' using a 5 MHz continuous wave Doppler, compared peak frequencies in normal and stenosed internal carotids with those predicted by a theoretical model. The formulation of practical suggestions for using peak frequency in predicting severity of stenosis was beyond the scope of their work; nonetheless, the wide variation evident in their data suggests that precise assessment of stenosis is not possible with peak Doppler frequencies.The objectives of our study were to further investigate the relationship of peak frequency and carotid stenosis and, in particular, to develop practical suggestions for the use of peak frequency in clinical evaluation of cervical carotid occlusive disease. Materials and MethodsSeventy-five cervical carotid stenoses were identified in which the degree of lumen narrowing could be accurately measured from carotid arteriograms and in which good quality spectral analysis could be obtained from recorded Doppler signals. Fifty-eight of these stenoses were located in the internal, 12 were in the external and 6 were in the common carotid artery. Calipers were used to measure the lumen diameter in *Hereafter termed peak frequency or peak systolic frequency. the stenotic and non-stenotic zones on AP and lateral selective carotid arteriograms ( fig. 1A). The arteriograms were measured blindly by two independent observers. If the measurements disagreed by more than 0.5 mm, the films were remeasured by a third independent observer in an e...
Duplex ultrasound (US) scans of 110 carotid arteries ipsilateral to hemispheric strokes were compared with scans of 90 asymptomatic vessels in the same patients to determine the relative prevalence of stenotic lesions. In addition, scans of paired carotid arteries in patients with stroke involving only one cerebral hemisphere were compared to determine whether the incriminated side demonstrated a greater degree of stenosis than the asymptomatic side. The duplex US findings demonstrated a positive correlation between stenosis and hemispheric stroke. However, only 20% of carotid arteries ipsilateral to hemispheric stroke showed a reduction in diameter greater than 70%, compared with 5% of asymptomatic vessels. A minimal difference was demonstrated between the symptomatic and asymptomatic groups with respect to lesser degrees of stenosis. In paired carotid arteries, the degree of stenosis of the symptomatic vessel exceeded that of the asymptomatic vessel in only 43% of cases. These results suggest that the prevalence of severe carotid stenosis in stroke patients has been previously overestimated. The findings also emphasize the need for further investigation of other plaque-related risk factors that may enhance stroke prevention through improved selection of surgical or medical therapy. Factors currently under investigation include plaque ulceration, intraplaque hemorrhage, plaque echogenicity, and the effects of sequential stenoses.
Fifty errors with Doppler examination of 356 carotid bifurcations were examined to determine their cause and to establish methods of prevention. Only those errors related to hemodynamically significant stenosis or complete occlusion were considered. The relative frequency of errors in diagnosis of occlusion (30 false-positive or negative versus 31 true-positive) was considerably greater than the rate of inaccuracy for diagnosis of hemodynamically significant stenosis (20 false-positive or-negative versus 89 true-positive). The high error rate in diagnosis of occlusion was attributed to reliance on negative information. The source of error could be established in 48 of the 50 cases. In all but three cases, potential for preventing error existed through use of additional noninvasive techniques such as examination of common carotid resistivity or use of oculoplethysmography. Twenty-two errors of localization of stenosis or occlusion were encountered in addition to the 50 false-positive and -negative errors. In three of these, the errors might have led to patient mismanagement.
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