Objectives: This study examined the relationship between chronic refractory (CR) in-stent restenosis (ISR) and metal allergic reaction. Background: Although drug-eluting stent reduced the restenotic event compared with bare-metal stent, the mechanism of neointimal proliferation is not clear yet; however, bare-metal stent still remains as one of the choices. Methods: Of 128 bare-metal stent implanted patients who experienced target lesion revascularization at least once, 60 patients with the second ISR (study group) and 68 patients without the second ISR (control group) were compared in terms of result from the skin patch test for metal allergic reaction. Results: Nickel was dominant among components of 316L stainless steel. The nickel-positive was observed in 19% (24/128) of all patients. Of 24 nickel-positive, 18 (30%) was in the study group, whereas 6 (9%) was in the control group (P=.02). According to multivariate analysis, the most significant predictor for CR-ISR was reference vessel diameter (P=.0010) followed by nickel-positive (P=.0033) and hyperlipidemia (P=.0305). The nickel-positive showed the highest odds ratio of 5.41 adjusted with confounder variables. Conclusion: This study with the second ISR showed that nickel was a major factor for CR-ISR. Further improvement of biocompatible material is required for coronary stents and strut-coating materials even in the drug-eluting stent era.
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