Assessment of stenosis: implications of variability of Doppler measurements in normal-appearing carotid arteries.

PURPOSE

To examine the variability of Doppler measurements along the extra-cranial courses of the nondiseased common carotid artery (CCA) and internal carotid artery (ICA) and determine the effect of this variability on assessment of carotid arterial stenosis.

MATERIALS AND METHODS

During the study period, 580 patients were referred for carotid arterial ultrasonography (US), including Doppler measurements of flow velocities in the proximal, middle, and distal portions of the CCA, in the bulb, and in the proximal and distal portions of the ICA. Eighty-five patients (average age, 59 years) with normal ICAs and CCAs formed the cohort for this study.

RESULTS

The range of peak systolic velocity (PSV) measurement (maximum minus minimum) averaged 20 cm/sec +/- 13 in the CCA and 15 cm/sec +/- 13 in the ICA. ICA/CCA velocity ratios varied, depending on the CCA measurement location. In five arteries, PSV ratios exceeded a threshold of 1.8 (suggesting > or = 60% stenosis); in 23 arteries, end diastolic velocity ratios exceeded a threshold of 2.4 (also suggesting > or = 60% stenosis). Right-to-left CCA PSV ratios were abnormal in up to 26 patients (suggesting > 50% ICA stenosis), depending on where CCA measurements were obtained. When the CCA ratios were obtained at the same level, 16 were in the abnormal range.

CONCLUSION

Variability of Doppler measurements in the CCA and ICA in patients without visible disease is substantial and could lead to inaccuracies in carotid arterial stenosis assessment.