Grading carotid intrastent restenosis: a 6-year follow-up study.

Background and Purpose: The accuracy of carotid ultrasound has not been well established in predicting intrastent restenosis (ISR) after carotid artery stenting (CAS). The aim of this study is to determine different degrees of ISR using ultrasound velocity criteria compared to percentage of stenosis at angiography.
Methods: This is a 6-year prospective study. After CAS procedure, each patient underwent angiography for measuring ISR (NASCET method) which was compared to peak systolic velocity (PSV), end diastolic velocity (EDV), and the ratio between PSV of internal carotid artery and common carotid artery (ICA/CCA). This was done within 48 hours, thus creating a baseline value. Ultrasound (US) examination was performed at day 30, at 3, 6, 9, and 12 months, and then yearly. Patients with an increase in PSV greater than 3 times the baseline value or in presence of PSV >or=200 cm/s underwent angiography.
Results: 814 CAS procedures, 6427 US examinations, and 1123 angiographies were performed. ISR >or=70% and ISR >or=50% was detected, respectively, in 22 patients and in 73 patients. We defined velocity criteria for grading carotid ISR: PSV <or=104 cm/s, if <30% stenosis; PSV:105 to 174 cm/s if 30% to 50% stenosis; PSV:175 to 299 cm/s if a 50% to 70% stenosis; PSV >or=300 cm/s, EDV >or=140 cm/s, and ICA/CCA >or=3.8 if a >or=70% stenosis. Receiver operator characteristic (ROC) curves for ISR >or=70% were, respectively, for PSV, EDV, and ICA/CCA: 0.99, 0.98, and 0.99.
Conclusions: US grading of carotid ISR can guarantee a correct follow-up after CAS if new customized velocity criteria are validated by skilled operators using a specific protocol of follow-up in a certified laboratory.