Misclassification of carotid stenosis severity with area stenosis-based evaluation by computed tomography angiography: impact on erroneous indication to revascularization or patient (lesion) migration to a higher guideline recommendation class as per ESC/ESVS/ESO/SVS and CMS-FDA thresholds

Intoduction: Despite a growing understanding of the role played by plaque morphology, the degree of carotid lumen reduction remains the principle parameter in decisions on revascularization in symptomatic and asymptomatic patients. Computed tomog-raphy angiography (CTA) is a widely used guideline-approved imaging modality, with "percent stenosis" commonly calculated as %area reduction (area stenosis - AS).Aim: We evaluated the impact of the non-linear relationship between diameter stenosis (DS) and AS (area = pi center dot (diameter/2)2, so that in concentric lesions 51%AS is 30%DS and 75%AS is 50%DS) on stenosis severity misclassification using calculation of area reduction.Material and methods: CTA and catheter quantitative angiography (cQA) were performed in 300 consecutive patients referred to a tertiary vascular centre for potential carotid revascularization (age: 47-83 years, 33.7% symptomatic, 36% female; referral stenosis of >= "50%"). CTA-AS was determined by agreement of 2 experienced radiologists; cQA-DS (pivotal trials standard reference, NASCET method) was calculated by agreement of 2 corelab analysts.Results: For symptomatic lesion thresholds, CTA-AS-based calculation reclassified 76% of "< 50%" cQA-DS measurements to the "50-69%" group, and 58% of "50-69%" measurements to the ">= 70%" group. For asymptomatic lesion thresholds, 78% of "< 60%" cQA-DS measurements were reclassified to the "60-79%" group, whereas 42% of "60-79%" cQA measurements crossed to the ">= 80%" class. Overall, employing CTA-AS instead of cQA-DS enlarged the "60-79%" and ">= 80%" lesion severity classes 1.6-and 5.8-fold, respectively, whereas the ">= 70%" class increased 4.15-fold.Conclusions: Replacing the pivotal carotid trials reference standard cQA-DS "%stenosis" measurement with CTA-AS-based "%stenosis" results in a large-scale lesion/patient erroneous gain of an "indication" to revascularization or migration to a higher revascularization indication class. In consequence, unnecessary carotid procedures may be performed in the absence of cQA verifi-cation. Until guidelines rectify the "%stenosis" measurement methods with different guideline-approved imaging modalities (and, where needed, re-adjust decision thresholds), CTA-AS measurement should not be used as a basis for carotid revascularization.