Review of Distal Embolism with Respect to Filters for Carotid Artery Stenting

Objective: Carotid artery stenting is performed using a device for preventing distal embolism because vasodilationrelated debris may cause cerebral infarction. Concerning filters for preventing embolism, membrane-type filters have been used, but mesh-type filters became commercially available. We have selected filter-assisted stenting as a first-choice procedure. We examined post-treatment filters under a microscope, and reviewed the pathogenesis of distal embolism. Methods: The subjects were 83 patients in whom carotid artery stenting with a filter was performed, and filters could be examined after surgery (Angioguard XP [AG; Cordis Corporation, Miami Lakes, FL, USA]: 25 patients, Filterwire EZ [FW; Boston Scientific, Natick MA, USA]: 32, and Spider FX [Spider; Covidien, Dublin, Ireland]: 26). After treatment, the filters were stained with hematoxylin and eosin (HE), separated from the struts, and embedded in preparations for microscopic observation. Debris was classified into plaque-derived and fibrin-formation types, and quantified as an area using computer software. Distal embolism was evaluated based on intraoperative flow impairment, postoperative symptoms, and perioperative diagnostic imaging findings. Results: Intraoperative flow impairment was noted in six patients (24%) in the AG group, five (15.6%) in the FW group, and one (3.8%) in the Spider group. Cerebral infarction was observed in three (12%), two (6.3%), and two (7.6%) patients, respectively. There were no differences in the volume of plaque-derived debris, but the volume of fibrin-formation-type debris was more in the AG group. As a result, the volume of debris collected was more. In the Spider group, the volume of fibrin-formation-type debris was minimum. Conclusion: Functions differed between the membrane-type and mesh-type filters. Considering their performance, these filters should be used.