The best method to quantitate angiographic carotid artery stenosis?

Stroke welcomes Letters to the Editor and will publish them, if suitable, as space permits. They should not exceed 1,000 words (excluding references) and may be subject to editing or abridgment. Please submit letters in duplicate, typed double-spaced. Include a fax number for the corresponding author. To the Editor: We read with interest the recent report by Alexandrov et al 1 and the editorial by Barnett and Warlow 2 concerning the measurement of carotid artery stenosis. After comparison between the duplex method and various angiographic measurements, Alexandrov and colleagues strongly advocated the duplex method. However, as the editorial points out, the results of NASCET 3 and ECST 4 have set the standard of indication for carotid endartercctomy (CEA) based on angiographic measurements only. It is well known that the formulas used by NASCET 3 and ECST 4 ' 3 give different measures of the degrees of stenosis in the same arteriogram. 1-3-6 ' 7 So far, most comparative studies between these two measurement methods have been limited to the group of severely and moderately stenosed bifurcations. Yet the threshold between mild and moderate stenosis may become more important, depending on the final outcome of the ongoing trials: how close to 30% will the limit be when surgery is recommended? In routine clinical work, a gTeat part of the bifurcations evaluated by angiog-raphy belong to these groups of mild and moderate degrees of stenosis. It is therefore important to compare the two most widely used methods for measuring angiographic carotid artery stenosis in an unselected group of symptomatic patients with all degrees of stenosis. With this aim, we evaluated the selective intra-arterial digital subtraction angiography films of 41 consecutive patients with hemispheric or retinal transient ischemic attacks or nondisabling stroke. Three observers measured the stenosis degree according to the NASCET and ECST criteria. In most cases three projections of each bifurcation were available, and the first observer selected the image of each bifurcation to be measured by all three investigators. Both measurements, using a magnifying glass film viewer, were independently performed twice by each observer with at least 3 weeks' interval between the separate sessions. After exclusion of two nondiagnostically imaged bifurcations, 80 bifur-cations thus underwent 480 pain of measurements. For statistical analysis, the measured stenosis percentages were divided into four clinically relevant classes: mild (0 to 29%), moderate (30% to 69%) or severe (70% to 99%) stenosis or occluded. The …