BACKGROUND Inflammation might contribute to the development of stent thrombosis (ST). The association between inflammatory cytokine concentrations and drug-eluting ST were evaluated.

METHODS AND RESULTS Among the 123 ST patients enrolled in the multicenter Korea Stent Thrombosis registry, plasma samples were available in 41 patients. The patients' clinical characteristics and plasma concentrations of monocyte chemoattractant protein-1, tumor necrosis factor-alpha, and interleukin (IL)-6 were compared with 81 matched controls. Although the concentrations of 3 cytokines were higher in the ST group, they did not have significant differences. When divided into quartiles, the proportion of patients with the highest quartile of IL-6 was higher in the ST group than in the control group (44% vs. 16%, P = 0.001), and the highest IL-6 quartile was an independent predictor of ST for both early (adjusted hazard ratio [HR] 6.96; 95% confidence interval [CI] 1.75-27.66) and late ST (adjusted HR 4.71; 95%CI 1.06-20.92). In addition, the highest IL-6 quartile was an independent predictor of ST in those on clopidogrel (adjusted HR 7.70; 95%CI 1.97-30.13) but not in those who were off clopidogrel.

CONCLUSIONS Highest IL-6 quartile was associated with ST, especially in clopidogrel users regardless of the time of ST, suggesting the involvement of inflammatory cytokines in ST.