Influence of the angiographic internal carotid artery stenosis assessment method on indicating carotid surgery

Background: To estimate the influence of different kinds of angiographic internal carotid artery (ICA) stenosis assessment methods on clinical decision making on carotid surgery. Method: One hundred angiographically proven ICA lesions in 65 patients (54 men, 11 women, mean age +/-SD, 64+/-8 years) were evaluated by simultaneous biplane angiography. The angiograms were analyzed using three kinds of linear diameter reduction methods [North American (NASCET), and European (ECST) carotid surgery trial method, common carotid artery method(CC)], and five area reduction methods reflecting more accurately the anatomical degree of stenosis [squared NASCET, ECST and CC (N-2, E-2, CC2), combined stenosis estimation of two projections (NASCET-bi, ECST-bi)]. All lesions were additionally evaluated by continuous wave (cw-)Doppler ultrasound prior to angiography. Between method agreement on classifying the lesions into stenosis < 70% and into stenosis greater than or equal to 70% was calculated by means of kappa statistic. Results: The degree of stenosis (median and inter-quartile range) ranged between 65% (38-82) by means of NASCET and 91% (87-93) by means of CC2. Thirty-seven ICA stenoses would have been operated using NASCET, but 82 using CC2. Between method agreement on assessing high grade ICA stenosis ranged from poor (kappa value 0.17 for the pair NASCET/CC2) to excellent (kappa value 0.92 for the pair NASCET-bi). Cw-Doppler ultrasound showed a good agreement (kappa value 0.72-0.80) with all angiographic methods using an area reduction formula apart from CC2. The agreement was moderate between cw-Doppler and NASCET and ECST respectively. Conclusion: The clinical decision to operate on an ICA stenosis will strongly be influenced by the angiographic method used. Because reliable clinical data exist only for the NASCET and ECST method these two angiographic stenosis assessment method should be used for clinical decision making.