Utility and accuracy of duplex ultrasonography in evaluating in-stent restenosis after carotid stenting

Background: Stents alter flow velocities after carotid artery stenting (CAS). To identify criteria for in-stent restenosis (ISR), velocities obtained by duplex ultrasonography (DU) after CAS were analyzed. Methods: Carotid angiography and DU were performed after 129 CAS procedures. The 2 × 2 table method and receiver operating characteristic curves were used to assess the ability of DU to detect ISR. Results: The median follow-up period was 21.2 months (interquartile range 14-32 months). Overall, 6 patients (4.7%) had significant ISR by angiography. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the validated criteria for nonstented arteries were 100%, 85%, 25%, and 100%, respectively, to determine ISR. Newly validated criteria revealed optimal detection of ISR, with 100% sensitivity, 99% specificity, PPV of 66%, and NPV of 100%. Patients with abnormal findings on initial DU revealed increased velocities by >80% when ISR occurred. Conclusions: DU can accurately detect ISR after CAS, but velocity criteria require modification and validation at each vascular laboratory. For patients with abnormal findings on initial DU, significant changes in velocities suggest ISR.