Background and purpose: In-stent restenosis (ISR) caused by in-stent intimal hyperplasia (ISH) may develop after carotid artery stenting (CAS), and often necessitates re-stenting. We investigated whether new ultrasound technique is useful for detecting carotid artery plaques prone to ISR.
Purpose: Superb micro-vascular imaging (SMI) is a new color Doppler imaging technique for assessing low velocity blood flow such as neovascularization in carotid artery plaques. In this study, we attempted to identify associations between findings from carotid ultrasonography with SMI performed prior to CAS and in-stent restenosis after 6 months of CAS.
Methods: This study investigated 19 patients (18 men; mean age, 72.4 years). Preoperative plaque evaluation was performed by magnetic resonance imaging, ultrasonography, and carotid angiography. Follow up angiography was performed in all patients at 6 months after CAS. ISR was defined as ISH resulting in >50% stenosis based on European Carotid Surgery Trialists criteria. We investigated whether SMI was useful as a predictor of ISR by chi-square test.
Results: Preoperative mean stenosis rate according to North American Symptomatic Carotid Endarterectomy Trial methods in 19 patients was 61.3%. Neovascularization was observed on SMI in 10 patients (52.6%). Carotid angiography at 6 months after CAS revealed ISR in 4 patients, all of whom had shown neovascularization on SMI. A significant association was seen between findings of neovascularization on SMI and development of ISR (p = 0.033). In predicting ISR, neovascularization findings on SMI offered 100.0% sensitivity and 60.0% specificity.
Conclusions: Preprocedural plaque characterization by carotid ultrasound with SMI appears useful for predicting ISR at 6 months after CAS.
Keywords: Carotid artery stenting; Carotid ultrasonography; In-stent intimal restenosis; Neovascularization; Superb microvascular imaging.
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