[en] Objective To assess polymorphonuclear neutrophils activation after stenting in acute coronary syndromes studied by myeloperoxydase, lactoferrin and elastase release in this clinical setting. Methods Myeloperoxydase, lactoferrin, elastase, C-reactive protein and cytokines serum levels were assessed in 20 patients undergoing catheterization for unstable angina. Serial sampling starting before arteriography and continued up to 24 h was carried out in 15 patients undergoing direct stenting (group A) and in five patients assessed by coronary angiography only (group B). Results Myeloperoxydase, lactoferrin and elastase levels remained unchanged following catheterization, whereas a significant increase in myeloperoxydase (P=0.0009) and lactoferrin (P=0.004) was observed after stenting. No change in levels of tumour necrosis factor alpha, interleukin (IL)-8 and IL-12 was found in group B after catheterization at the different sampling times, although IL-8 and IL-12 levels increased transiently following stenting. IL-6 values increased in both groups. Baseline values of C-reactive protein were similar in each group. A progressive increase in C-reactive protein was noted in both groups and appeared to be larger following stenting (group A: P=0.0002; group B: P=0.01). Conclusions In patients with unstable angina, stenting is associated by immediate neutrophil activation followed by release of inflammatory cytokines (IL-6, IL-8, IL-12) and C-reactive protein elevation. This study points out a potential role of myeloperoxydase as a trigger for inflammatory reaction in patients with unstable coronary syndromes undergoing percutaneous coronary intervention. (C) 2005 Lippincott Williams WillZins.