Comparison between degree of carotid stenosis observed at angiography and in histological examination

Summary

Background. The generally accepted indications for carotid endarterectomy are the clinical picture and degree of per cent stenosis of the carotid artery. Despite the fact that stenosis measurement is defined, the methods vary considerably. The correlation of particular methods, especially angiography and duplex sonography, has been repeatedly demonstrated. However, the correlation between any technique and true anatomical stenosis, as evaluated on the surgical specimen, has been only anecdotally reported.

Method. During carotid endarterectomy, the atherosclerotic plaque was removed in one piece and subsequently stored and histologically processed. The histological slides were evaluated under an optical microscope, scanned and the slide with maximum stenosis was determined using a planimetric program. Both the minimal lumen area and the area of the whole plaque were measured. The stenosis was calculated using the planimetric method. On the maximum stenosis slice, the minimal diameter and the diameter of the whole plaque were also measured. Angiographic images were scanned and the per cent stenoses were remeasured, according to the NASCET and ECST criteria. In total, of 147 cases, all above-mentioned parameters were obtained. Student’s t tests for paired samples were used to evaluate the results.

Findings. The t-tests indicated significant differences between the per cent stenosis as measured on the anatomical specimen and on the angiogram (p<0.05). The results indicate that the angiographic measurement underestimates the degree of in-situ anatomical stenosis. The underestimation was more marked the less the degree of stenosis.

Conclusions. Our study finds that per cent stenosis measurement obtained by angiography with NASCET or ECST methods does not reliably reflect the anatomical degree of per cent stenosis, which makes questionable the rigorous following of percentage stenosis using angiography as the sole indicator for carotid endarterectomy in all cases.