Clinical Impact of External Carotid Artery Remodeling Following Carotid Artery Stenting

<b>Background</b>: Carotid artery stenting (CAS) is a common revascularization approach for carotid artery stenosis. While its impact on the internal carotid artery (ICA) has been extensively studied, the effects on the external carotid artery (ECA)-a key collateral pathway for cerebral perfusion-remain insufficiently explored. This study aimed to assess structural changes in the ECA following CAS and their clinical significance. <b>Methods</b>: A retrospective observational cohort study of 963 patients treated with CAS between 2018 and 2024 was conducted. Demographic data, comorbidities, and procedural characteristics were collected. Pre- and postprocedural ICA and ECA diameters were measured via angiography. Spearman's correlation, regression modeling, and receiver operating curver (ROC) analysis were used to identify predictors of ECA narrowing and occlusion and their relationship with neurological outcomes. <b>Results</b>: The median ECA diameter decreased post-CAS (from 4.7 mm to 3.8 mm, <i>p</i> < 0.001). ECA overstenting occurred in 96.4% of cases, with 71.7% exhibiting diameter reduction. De novo ECA occlusion occurred in 2.5% of patients and was associated with a higher incidence of stroke, transient ischemic attack, and in-stent restenosis (ISR). Multivariate analysis identified preoperative ECA diameter (<i>p</i> < 0.001), ICA diameter (<i>p</i> = 0.001), and second-generation stents (<i>p</i> = 0.02) as independent predictors of ECA narrowing. ROC analysis confirmed that a preoperative ECA diameter ≤ 3.05 mm strongly predicted occlusion (Area under the curve (AUC) = 0.93, <i>p</i> < 0.001). <b>Conclusions</b>: CAS frequently leads to ECA remodeling, including occlusion, compromising collateral perfusion and contributing to adverse ischemic incidences and ISR. Preprocedural ECA assessment may aid in optimizing patient selection and procedural planning.