Background: An elevated C-reactive protein (CRP) level plays a crucial role in cell biology of atherosclerosis and unstable plaque formation. However, direct evidence of CRP involvement in atherosclerotic plaque development and vulnerability is still limited. We hypothesized that CRP is present in the vulnerable plaques and that CRP staining intensity is stronger in vulnerable plaques compared to stable plaques.
Methods: Directional coronary atherectomy (DCA) was performed on 58 patients with stable angina (group 1) and 40 patients with unstable angina (group 2). White blood cell (WBC) counts were measured prior to DCA. Immunohistochemical staining (IHCS) was performed to localize CRP in the atheroma. Staining intensity in macrophages and extracellular tissue was graded as: 0, no staining; 1+, < 30%; 2+, 30%-60%; 3+, > 60%.
Results: The IHCS demonstrated that CRP staining - 1+ intensity in macrophages and extracellular tissue were significantly higher in group 1 than in group 2 patients (all p values < 0.0001). However, IHCS demonstrated that CRP staining a 2+ intensity in macrophages and extracellular tissue were significantly higher in group 2 than in group 1 patients (all p values < 0.0001). By multiple analysis, only stable angina was independently associated with CRP staining : 1+ intensity in both macrophages and extracellular tissue (p < 0.0001), whereas unstable angina and WBC counts were independent predictors of CRP staining > or = 2+ intensity in both macrophages and extracellular tissue (p < 0.0001).
Conclusion: CRP was frequently found in atherosclerotic plaques of patients with unstable angina. This analytical finding suggests that CRP directly mediates an inflammatory process in the atherosclerotic plaque.