Usefulness of high-sensitivity C-Reactive protein in predicting long-term risk of death or acute myocardial infarction in patients with unstable or stable angina pectoris or acute myocardial infarction

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Abstract

High-sensitivity C-reactive protein (CRP), proposed as a new coronary risk marker, may reflect either an acute phase reaction or the level of chronic inflammation. Thus, CRP may be less predictive of long-term outcomes when measured after acute myocardial infarction (AMI) than after unstable angina pectoris (UAP) or stable angina pectoris (SAP). A total of 1,360 patients with severe coronary artery disease (≥1 stenosis ≥70%) had CRP levels obtained at angiography. Presenting diagnoses were SAP (n = 599), UAP (n = 442), or AMI (n = 319). During follow-up (mean 2.8 years), death or nonfatal AMI (D/AMI) occurred in 19.5%, 16.1%, and 17.2% (p = NS) with SAP, UAP, and AMI, respectively. Corresponding median CRP levels were 1.31, 1.27, and 2.50 mg/dl (p <0.001). For the overall cohort, increasing age, low ejection fraction, revascularization, and elevated CRP were the strongest of 6 independent predictors for D/AMI. Among those presenting with SAP, CRP levels above the first tertile were associated with an adjusted hazard ratio of 1.8 (95% confidence interval [CI] 1.2 to 2.8, p <0.009) for D/AMI. After UAP, the hazard ratio was 2.7 (95% CI 1.4 to 5.0, p <0.002). However, when measured during hospitalization for AMI, CRP was not predictive of long-term outcome (hazard ratio 1.0 [95 % CI 0.5 to 1.7] p = 0.86). In conclusion, predischarge CRP levels are higher after AMI than after UAP or SAP. However, whereas CRP is strongly predictive of long-term D/AMI for patients presenting with SAP or UAP, it is not predictive shortly after AMI, suggesting that measurements should be delayed until the acute phase reaction is over and levels have returned to baseline.

Section snippets

Study objectives and hypotheses

Our objectives were to test (1) whether CRP is equally predictive of long-term clinical outcomes (death [D] or AMI) in patients with angiographically similar CAD presenting with AMI as in those presenting with stable angina pectoris (SAP) or unstable angina pectoris (UAP), and (2) whether the predictive value of CRP overall and in the specific diagnostic subgroups is altered by adjustment for multiple standard risk factors. We postulated that CRP values would be higher after AMI than after SAP

All patients

Baseline demographics of the 1,360 patients with CAD overall and by diagnostic subgroup are summarized in Table 1. Patients averaged 65 years of age (range 33 to 95), and 77% were men. After AMI, ejection fraction, blood pressure, and lipid levels were lower and CRP higher; however, there were no significant differences among groups in the number of severely stenotic coronary vessels and in D/AMI events.

For the overall cohort, CRP was a highly significant univariable and multivariable

Study perspective

In our large CAD cohort with up to 5 years follow-up, we found that CRP was strongly predictive of long-term outcome in patients with SAP and UAP, but not after recent AMI despite higher levels (2.5 vs 1.3 mg/dl). Because the 3 CAD subgroups had comparable angiographic CAD and therapy, we interpret this failure in the AMI group as reflecting a distortion in chronic levels caused by the acute phase reaction associated with myocardial injury. In non-AMI patients, the adjusted relative hazard of

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    This study was supported in part by the Deseret Foundation, Intermountain Health Care, Salt Lake City, Utah; and by Grant 5T32HL07576 from the National Heart, Lung, and Blood Institutes, National Institutes of Health, Bethesda, Maryland.

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