The incidence of carotid in-stent stenosis is underestimated ≥50% or ≥80% and its clinical implications

The incidence of carotid in-stent stenosis has been reported to vary between 1% and 30%. Most published studies have short follow-up, which may lead to underestimation of the incidence of in-stent stenosis. This study analyzed the incidence of ≥50% and ≥80% in-stent stenosis using validated duplex ultrasound criteria and its clinical implications. This is a retrospective analysis of prospectively collected data of 450 carotid artery stenting (CAS) procedures (February 6, 2001-December 19, 2016). All patients had postoperative carotid duplex ultrasound examination, which was repeated at 1 month, 6 months, and every 6 to 12 months thereafter. A Kaplan-Meier analysis was used to estimate rates of freedom from ≥50% in-stent stenosis (internal carotid artery peak systolic velocity of ≥224 cm/s) and ≥80% in-stent stenosis (internal carotid artery peak systolic velocity of ≥325 cm/s), freedom from reintervention, and survival. The mean age was 68.3 years, with a mean follow-up of 40.3 months. A total of 201 patients (45% [201/450]) had CAS for symptomatic disease. Primary CAS was done in 291 patients (65%); in the remaining 35%, CAS was done for postcarotid endarterectomy (CEA) stenosis. A total of 101 patients (23%) had ≥50% late carotid in-stent stenosis, and of these, 33 (7.4%) had ≥80% in-stent stenosis. Nineteen patients (4.3%) developed late transient ischemic attack and three (0.7%) late stroke. Twenty-three (5.2%) patients had late reintervention. Rates of freedom from ≥50% in-stent stenosis in the whole series were 85%, 79%, 75%, 72%, and 70% at 1 year, 2 years, 3 years, 4 years, and 5 years, respectively. The rates of freedom from ≥50% in-stent stenosis for primary CAS and CAS for post-CEA stenosis were not statistically significant (P = .540). The rates of freedom from ≥80% in-stent stenosis for the whole series were 96%, 95%, 93%, 90%, and 89% at 1 year, 2 years, 3 years, 4 years, and 5 years, respectively. The rates of freedom from ≥80% in-stent stenosis for primary CAS and CAS for post-CEA stenosis were also not statistically significant (P = .516). Rates of freedom from reintervention were 98%, 96%, 93%, 93%, and 91% at 1 year, 2 years, 3 years, 4 years, and 5 years, respectively, and there were no significant differences between primary CAS and CAS for post-CEA stenosis (P = .939). The overall late survival rates were 99%, 97%, 96%, 94%, and 91% at 1 year, 2 years, 3 years, 4 years, and 5 years. The incidence of ≥50% in-stent stenosis is relativel