Circulating monocytes and in-stent neointima after coronary stent implantation

OBJECTIVES: The aim of this study was to investigate the relationship between circulating monocytes and in-stent neointimal volume at six-month follow-up. BACKGROUND: In-stent neointimal hyperplasia is the main contributing factor to in-stent restenosis. There is increasing evidence that white blood cells (WBCs), especially monocytes, play a central role in restenosis after stent implantation. METHODS: We performed coronary stent implantation in 107 patients (107 lesions). Peripheral blood was obtained from all patients immediately before coronary angiography and every day for seven days after the intervention, and each WBC fraction count was analyzed. At scheduled six-month follow-up, all patients received angiographic and volumetric intravascular ultrasound analysis. RESULTS: The circulating monocyte count increased and reached its peak two days after stent implantation (from 350 +/- 167 to 515 +/- 149/mm3, p < 0.01). The maximum monocyte count after stent implantation showed a significant positive correlation with in-stent neointimal volume at six-month follow-up (r = 0.44, p < 0.0001). Other fractions showed neither significant serial changes nor a correlation with in-stent neointimal volume. Multiple regression analysis revealed that in-stent neointimal volume was independently correlated with stent volume immediately after implantation (r = 0.45, p < 0.0001) and maximum monocyte count (r = 0.35, p < 0.001). Angiographic restenosis, defined as percent diameter stenosis >50%, was observed in 22 patients (21%), and these patients showed a significantly larger maximum monocyte count than patients without restenosis (642 +/- 110 vs. 529 +/- 77/mm3, p < 0.01). CONCLUSIONS: Circulating monocytes increased after coronary stent implantation, and the peak monocyte count related to in-stent neointimal volume. Our results suggest that circulating monocytes play a role in the process of in-stent neointimal hyperplasia.