Quantifying stenosis of the internal carotid artery:: Which ultrasound criteria are relevant?

Therapeutic decisions in cases of arteriosclerotic stenosis of the internal carotid artery usually depend mainly on the degree of stenosis. However, the recommendations with regard to suitable ultrasonographic criteria are so controversial that even authors of repute describe "confusion" and "chaos in methodology". Aim: The aim of this study is to assess which of the most frequently recommended sonographic criteria for stenosis best fulfill the requirements of an exact quantification of stenoses of the internal carotid artery. Method: In 42 consecutive cases the pre-operative ultrasound findings were compared with the degree of stenosis in surgically removed specimens. The sonographic technique employed consisted of the analysis of 2 direct and 3 indirect hemodynamic criteria of stenosis. In 34 of these cases planimetry was performed, too. The specimens were obtained by eversion thrombendarteriectomy or arteriotomy; for determination of the degree of stenosis a Paladur molded cylinder was prepared and measured. Results: Quantification of the haemodynamic criteria carries provided well with the endarterectomy specimens. Only in two cases there was a deviation of more than 10%: however, in these two cases a change with time in the degree of stenosis was probably responsible for the discrepancy. In contrast, planimetry usually underestimated the degree of stenosis: In 61% of the findings the ultrasonographic results differed by more than 10% from the reference standard. Conclusion: Quantification of stenosis of the internal carotid artery should be made using a combination of direct and indirect haemodynamic ultrasonographic criteria.