C-reactive protein increase in unstable coronary disease cause or effect?

A crucial point in understanding the clinical and pathophysiologic meaning of C-reactive protein (CRP) elevation in acute coronary syndromes (ACS) is whether CRP release is predominantly a response to even small amounts of myocardial necrosis, for which troponin is a sensitive and specific marker, or is an independent indicator of the inflammatory process occurring in that clinical condition. Whereas troponin is a good predictor of both mortality and myocardial infarction (MI), although the highest values are associated with a decreased probability of MI, CRP predicts mortality but has no relation with the early or late occurrence of MI. The large variability of CRP values in ACS may depend on the different response of this inflammation marker to various stimuli, some patients being particularly hyperresponsive, especially those with elevated CRP values at baseline. We hypothesize that myonecrosis, as detected by troponin increases, would represent the strongest stimulus for CRP increase in ACS, causing in some patients, especially those with already-elevated CRP values at baseline, a disproportionate increase of this marker. Accordingly, the highest CRP values during ACS are likely to be observed in patients with already-elevated CRP values at baseline (which would increase the probability of having death and MI in the follow-up) and the highest troponin values (which would increase the probability of death in the follow-up, but not of subsequent MI). This hypothesis would explain why high CRP levels in unstable coronary disease are good predictors of death, but not of MI.