Background Real-world data on low baseline low-density lipoprotein cholesterol (LDL-C) levels and long-term postdischarge cardiovascular outcomes in patients with acute coronary syndrome are limited. Methods and Results Of the 10 719 patients enrolled in the Korean registry of acute myocardial infarction between January 2004 and August 2014, we identified 5532 patients who were event free from death, recurrent myocardial infarction, or stroke during the in-hospital period after successful percutaneous coronary intervention. The co-primary outcomes were 3-point major adverse cardiovascular events (a composite of nonfatal stroke, nonfatal myocardial infarction, and cardiovascular death) and cardiovascular death at 5 years. Of 5532 patients with acute myocardial infarction (mean age, 62.1±12.8 years; 75.0% men), 446 cardiovascular deaths (8.1%) and 695 three-point major adverse cardiovascular events (12.6%) occurred at 5 years. In the continuous analysis of LDL-C, the risk of cardiovascular events increased steeply as LDL-C levels decreased from 100 mg/dL. For categorical analysis of LDL-C (<70, 70-99, and ≥100 mg/dL), as LDL-C levels decreased, clinical outcomes worsened (237/3759 [6.3%] in LDL-C ≥100 mg/dL versus 123/1291 [9.5%] in LDL-C 70-99 mg/dL versus 86/482 [17.8%] in LDL-C <70 mg/dL for cardiovascular death; P-trend<0.001; and 417/3759 [11.1%] in LDL-C ≥100 mg/dL versus 172/1291 [13.3%] in LDL-C 70-99 mg/dL versus 106/482 [22.2%] in LDL-C <70 mg/dL for 3-point major adverse cardiovascular event; P-trend<0.001). In a Cox time-to-event multivariable model with LDL-C levels ≥100 mg/dL as the reference, the baseline LDL-C level <70 mg/dL was independently associated with an increased incidence of cardiovascular death (adjusted hazard ratio, 1.68 [95% CI, 1.30-2.17]) and 3-point major adverse cardiovascular event (adjusted hazard ratio, 1.37 [95% CI, 1.10-1.71]). Conclusions In this Korean acute myocardial infarction registry, the baseline LDL-C level <70 mg/dL was significantly associated with an increased incidence of long-term cardiovascular events after discharge. (COREA [Cardiovascular Risk and Identification of Potential High-Risk Population]-Acute Myocardial Infarction Registry; NCT02806102). Registration URL: https://www.clinicaltrials.gov/; Unique identifier: NCT02806102.

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