Background: C-reactive protein (CRP), which has been suggested to directly enhance inflammation in plaques, is rapidly synthesized and secreted in the liver 6 h after an acute inflammatory stimulus. Therefore, serum levels of CRP within 6 h after the onset of acute myocardial infarction (AMI) merely reflect a chronic and persistent inflammatory process and are not due to acute myocardial damage. We hypothesized that the serum CRP level, which would abnormally elevate thereafter, is followed by a plaque rupture in the clinical setting of AMI.
Methods and results: CRP was prospectively measured by high-sensitivity CRP assay (hs-CRP) in 157 consecutive patients (106 patients within 6 h, and 51 patients ≥ 6 h but < 12 h after the onset of AMI) with ST-segment elevation AMI undergoing primary percutaneous coronary intervention (PCI). Serum levels of hs-CRP were also measured in 30 patients with stable angina undergoing elective PCI and in 30 healthy control subjects. The serum level of hs-CRP was significantly higher in patients with an onset of AMI < 6 h than in patients with angina pectoris (2.7 ± 2.3 mg/L vs 1.4 ± 0.7 mg/L, p < 0.0001 [mean ± SD]) and in healthy subjects (2.7 ± 2.3 mg/L vs 1.0 ± 0.6 mg/L, p < 0.0001). There were no significant differences in serum levels of hs-CRP in patients with an onset of AMI ≤ 3 h than in those patients with an onset of AMI > 3 h but < 6 h (2.7 ± 2.5 mg/L vs 2.7 ± 2.2 mg/L, p = 0.87). However, the serum level of hs-CRP was significantly higher in patients with an onset ≥ 6 h than in patients with an onset < 6 h (14.1 ± 16.5 mg/L vs 2.7 ± 2.3 mg/L, p < 0.0001).
Conclusions: Serum levels of hs-CRP were significantly higher in patients with an onset of AMI < 6 h than in healthy subjects and in patients with angina pectoris undergoing PCI. The inflammatory process has been proved as one of the mechanisms causing plaque rupture. Elevated serum hs-CRP levels in patients with AMI < 6 h may portend vulnerable plaque rupture.