Background: Recent studies reported that red cell distribution width (RDW) is an independent predictor for major adverse cardiac events (MACEs) in patients with acute myocardial infarction (AMI). However, incremental predictive value of RDW to conventional risk factors for MACEs has not been fully investigated yet. Methods: Between November 2005 and January 2010, 1,596 post-MI patients (1,070 male; mean age = 64.5 ± 11.9 years-old) followed up more than 12-month were included in this observational study. Baseline levels of RDW were measured at the time of admission. The 12-month MACEs were defined as a composite of death and non-fatal MI. Results: During the follow-up, 212 (13.3%) MACEs including 174 (10.9%) death and 38 (2.4%) non-fatal MI occurred. The RDW levels were significantly higher in patients with 12-month MACEs (13.8±1.3% versus 13.3±1.2%, p<0.001). In Cox proportional hazard model, RDW (hazard ratio [HR] 1.191, 95% confidence interval [CI] 1.033–1.373; p=0.016) in addition to body mass index (HR 0.911, 95%CI 0.839–0.988; p=0.025), prior coronary heart disease (HR 2.247, 95%CI 1.376–3.670; p=0.001), serum creatinine (HR 1.230, 95%CI 1.085–1.393; p=0.001), and percutaneous coronary intervention (HR 0.269, 95%CI 0.161–0.449; p<0.001) were independent predictors for 12-month MACEs after adjustment for clinical characteristics, procedural data, and discharge medication. Adding RDW to conventional risk factors and hemoglobin levels significantly improved prediction for 12-month MACEs, as shown by the net reclassification improvement (0.297; p=0.012) and integrated discrimination improvement (0.0143; p=0.042). The likelihood ratio test showed that RDW added incremental predictive value to the combination of hemoglobin and conventional risk factors for 12-month MACEs (p=0.005). Patients were categorized into 4 groups according to quartiles of RDW at baseline; quartiles 1 (≤12.6%, n=445), quartiles 2 (12.7%-13.1%, n=364), quartiles 3 (13.2%-13.9%, n=400), and quartiles 4 (>13.9%, n=387). The 12-month MACEs increased as quartiles of RDW increased. In Cox proportional hazard model, adjusted HRs for 12-month MACEs were, from lowest (reference) to the highest quartile, 1, 4.240 (95%CI, 1.410-12.752; p=0.01), 4.363 (95%CI, 1.474-12.914; p=0.008), and 6.179 (95%CI, 2.097-18.205; p=0.001), respectively. Conclusion: In post-MI patients, baseline RDW levels at admission could provide increment predictive value to conventional risk factors for predicting 12-month death and non-fatal MI even after adjustment for hemoglobin.
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