Proposed angiographic criteria for measurement of vertebral artery origin stenosis: the vertebral origin treatment with endovascular therapy (VOTE) method.

Standard measurement criteria for vertebral artery origin (VAO) stenosis have not yet been established. We propose such criteria and report on interrater agreement using two measurement methods in a series of patients referred for endovascular therapy. Three experienced angiography raters independently reviewed magnified cerebral angiograms. The formula [1 - (Ds/Dn)] × 100 was used, where Ds is the diameter of the most stenotic portion of the lesion and Dn is normal vessel diameter. The first measurement method allows unrestricted use of the V1 segment for measurement of normal diameter. In the second method, normal diameter is measured in the first portion of the V2 segment with exclusion of any region of poststenotic dilatation. Ten consecutive patients with VAO stenosis were reviewed. The mean degree of stenosis was 71.9% (standard deviation, ± 10.7%) with the first method and 66.9% ± 10.6% with the second method. Average interrater agreement was 80% with the first method and 87% with the second method. The intraclass correlation coefficient (ICC) demonstrated greater interrater agreement when the tortuous proximal V1 segment was excluded in normal diameter measurement (ICC = 0.7750) compared with the unrestricted use of the V1 segment for normal diameter (ICC = 0.7256). The kappa statistic was the best among the 3 raters with 10% variance when the tortuous V1 segment was excluded, at 0.73 (overall agreement, 87%). Our findings indicate that excluding the tortuous V1 portion when measuring normal diameter improves interrater agreement and simplifies the measurement of high-grade VAO stenosis.