Incidence, Timing and Associated Factors of In-Stent Restenosis after CASPER Placement: A Single-Center Retrospective Study.

Objective: The CASPER stent (Terumo, Tokyo, Japan) is a dual-layer micromesh device designed to prevent plaque prolapse into the stent struts and reduce perioperative stroke risk. However, the in-stent restenosis (ISR) incidence and associated factors after CASPER placement in Japan remain insufficiently investigated. This study aimed to evaluate the ISR rate, timing, and associated factors after CASPER placement. Methods: Eighty consecutive patients who underwent carotid artery stenting with a CASPER stent at a single institution between March 2021 and December 2023 were retrospectively analyzed. Preprocedural plaque characteristics, procedural details, and follow-up carotid artery ultrasound findings were reviewed. ISR was defined as luminal narrowing ≥50% in patients with neurological symptoms attributable to the ISR lesion and ≥70% in patients without such symptoms. Results: Over a mean follow-up of 27.6 ± 9.9 months, ISR occurred in 10 patients (12.5%). ISR developed 1.8-16.4 months after the index procedure, with a median time of 8.5 months. Patients with ISR had lower plaque-to-muscle ratio (PMR) values on T1-weighted MRI than patients without ISR (1.45 vs. 1.90, p = 0.024). Furthermore, stent diameter was smaller in patients with ISR than in those without it (median 7.5 vs. 8.0 mm, p = 0.029). During follow-up beyond 30 days after stent placement, ipsilateral ischemic stroke tended to occur more frequently in patients with ISR than in those without it (20.0% vs. 2.9%, p = 0.056). Conclusion: In patients treated with CASPER, ISR occurred within the first 18 months after treatment. Lower PMR values and smaller stent diameters were associated with ISR in this cohort. Larger studies with long-term follow-up are required to confirm these findings and assess CASPER stent long-term outcomes.