ABSTRACT: BACKGROUND:Chronic kidney disease (CKD) is a risk factor for myocardial infarction (MI) and death. Our goal was to characterize the association between CKD severity and short-term outcomes and the use of in-hospital evidence-based therapies among patients with ST-segment elevation MI (STEMI) and non-ST-segment elevation MI (NSTEMI). METHODS AND RESULTS:The study sample was drawn from the Acute Coronary Treatment and Intervention Outcomes Network registry, a nationwide sample of STEMI (n=19 029) and NSTEMI (n=30 462) patients. Estimated glomerular filtration rate was calculated with the Modification of Diet in Renal Disease equation in relation to use of immediate (first 24 hours) therapies and early (first 48 hours) cardiac catheterization as well as in-hospital major bleeding events and death. Overall, 30.5% and 42.9% of patients with STEMI and NSTEMI, respectively, had CKD. Regardless of MI type, patients with progressively more severe CKD had higher rates of death. For STEMI, the odds ratio for stage 3a, 3b, 4, and 5 CKD compared with patients with no CKD was 2.49, 3.72, 4.82, and 7.97, respectively (P(trend)<0.0001). For NSTEMI, the analogous odds ratios were 1.81, 2.41, 3.50, and 4.09 (P for trend <0.0001). In addition, patients with progressively more severe CKD were less likely to receive immediate evidence-based therapies including aspirin, beta-blockers, or clopidogrel, were less likely to undergo any reperfusion (STEMI) or revascularization (NSTEMI), and had higher rates of bleeding. CONCLUSIONS:Reports over the past decade have highlighted the importance of CKD among patients with MI. Data from this contemporary cohort suggest that patients with CKD still receive fewer evidence-based therapies and have substantially higher mortality rates.