Plasma protein acute-phase response in unstable angina is not induced by ischemic injury

Background Elevated levels of C-reactive protein (CRP) are associated with an unfavorable clinical outcome in patients with unstable angina. To determine whether ischemia-reperfusion injury causes this acute-phase response, we studied the temporal relation between plasma levels of CRP and ischemic episodes in 48 patients with unstable angina and 20 control patients with active variant angina, in which severe myocardial ischemia is caused by occlusive coronary artery spasm. Methods and Results Blood samples were taken on admission and subsequently at 24, 48, 72, and 96 hours. All patients underwent Holter monitoring for the first 24 hours and remained in the coronary care unit under ECG monitoring until completion of the study. On admission, CRP was significantly higher in unstable angina than in variant angina patients (P<.001). In unstable angina, 70 ischemic episodes (1.5+/-2 per patient) and in variant angina 192 ischemic episodes (9.6+/-10.7 per patient) were observed during Holter monitoring (P<.001), for a total ischemic burden of 14.8+/-30.2 and 44.4+/-57.2 minutes per patient, respectively (P<.001). The plasma concentration of CRP did not increase in either group during the 96 hours of study, even in patients who had episodes of ischemia lasting >10 minutes. Conclusions The normal levels of CRP invariant angina, despite a significantly larger number of ischemic episodes and greater total ischemic burden, and the failure of CRP values to increase in unstable angina indicate that transient myocardial ischemia, within the range of duration observed, does not itself stimulate an appreciable acute-phase response.