Patterns of in-stent restenosis after carotid artery stenting: Classification and implications for long-term outcome

Objectives Factors predicting in-stent restenosis (ISR) and future need for target lesion revascularization (TLR) after carotid artery stenting (CAS) remain undetermined. We hypothesized that the patterns of restenotic lesions may provide prognostic information. In this study, we developed an ultrasound classification scheme for ISR based on lesion length and distribution and assessed factors that may predict the need for TLR. Methods Patients were followed up after CAS with B-mode ultrasound imaging, and ISR lesions (≥40% stenosis) were classified into type I (focal ≤10 mm end-stent lesions), II (focal ≤10 mm, intrastent), III (diffuse >10 mm, intrastent), IV (diffuse >10 mm proliferative, extending outside the stent), and V (total occlusion). The frequency of lesion types was assessed. Accuracy of the ultrasound classification was confirmed with angiography. We recorded patient (age, gender, comorbidities), lesion (severity, etiology, symptomatic status) and procedural features (type, number, length of stents), and the need for TLR. Results Eighty-five ISR lesions developed after 255 CAS procedures. Their percentage distribution was type I, 40; type II, 25.9; type III, 12.9; for type IV, 20; and type V, 1.2. Accuracy of the ultrasound classification was confirmed by angiography ( r2 = 0.82). Inter-rater agreement for the assignment of lesion type based on ultrasound was 0.88 (very good). TLR was performed in 13 that were ≥80% diameter reducing. On univariate analysis, the need for TLR was highest in type IV lesions (0%, 0%, 27.3%, and 58.8% [types I to IV, respectively]; P = .001). History of ISR (2.9%, 0%, 0%, and 41.2% [types I to IV]; P = .003) and diabetes mellitus (20.6%, 22.7%, 45.5%, and 52.9% [types I to IV]; P = .02) occurred more frequently with type IV ISR lesions. On multivariate analysis of all patient, lesion, and procedural characteristics, only the type of ISR (odds ratio, 5.1) and a history of diabetes (odds ratio, 9.7) were independent predictors of TLR. Conclusions The proposed classification accurately grades the magnitude of intimal hyperplasia after CAS and provides important prognostic information. Diffuse proliferative (type IV) ISR lesions and diabetes are important determinants of long-term outcome after CAS. This classification will facilitate a standardized description of recurrence after CAS and enable early identification of high-risk patients for additional monitoring, treatment, and investigation.