Background and purpose: Although in-stent protrusion is a potential risk factor for thromboembolism following carotid artery stenting, the correlation between in-stent protrusion and postoperative ipsilateral stroke has not been well examined. Materials and methods: We retrospectively reviewed 342 consecutive carotid artery lesions in 319 patients who underwent carotid artery stenting between April 2008 and April 2015. After excluding cases with carotid artery dissection and acute occlusion, 301 lesions in total of 277 patients were included in the analysis. We examined the association between in-stent protrusion, which was detected by intravascular ultrasound, and postoperative ipsilateral stroke within 30 days. Results: In-stent protrusion was observed in 47 (15.6%) lesions, of which postoperative ipsilateral stroke within 30 days occurred with 4 (8.5%) lesions. All these events occurred within 10 days after treatment. On the other hand, only 1 (0.39%) of the 256 lesions without in-stent protrusion showed this symptom, and the event occurred at 30 days after treatment. Thus, lesions with in-stent protrusion had a higher cumulative risk of ipsilateral stroke than those without in-stent protrusion (8.5% vs 0.4% at 30 days, log-rank P < 0.001). In-stent protrusion, which was more often seen in symptomatic lesions, was associated with a vulnerable plaque assessed by MRI. After adjustment for postoperative stroke risks such as symptomatic lesions, plaque vulnerability, age or sex, in-stent protrusion was still significantly associated with postoperative ipsilateral stroke within 30 days (OR = 27.03, P = 0.001). Conclusions: Postoperative ipsilateral stroke was observed more frequently in patients with demonstrated in-stent protrusion (ISP) following CAS.
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