Prognostic significance of baseline low-density lipoprotein cholesterol in patients undergoing coronary revascularization; A report from the CREDO-Kyoto registry

Background The impact of very low baseline levels of low-density lipoprotein cholesterol (LDL-C) on patients with coronary artery disease remains unclear. Therefore, we aimed to investigate the baseline characteristics and clinical outcomes of patients with low baseline LDL-C levels who had undergone coronary revascularization. Methods We enrolled 39439 patients of the pooled population from the CREDO-Kyoto registries Cohorts 1, 2, and 3. After excluding 6306 patients with missing baseline LDL-C data, the study population consisted of 33133 patients who had undergone their first coronary revascularization. We assessed the risk for mortality and cardiovascular events according to quintiles of the baseline LDL-C levels. Results Patients in the very low LDL-C quintile (< 85 mg/dL) had more comorbidities than those in the other quintiles. Lower LDL-C levels were strongly associated with anemia, thrombocytopenia, and end-stage renal disease. The cumulative 4-year incidence of all-cause death increased as LDL-C levels decreased (very low: 19.4%, low: 14.5%, intermediate: 11.1%, high: 10.0%, and very high:9.2%; P<0.001), which was driven by both the early and late events. After adjusting for baseline characteristics, the adjusted risks of the very low and low LDL-C quintiles relative to the intermediate LDL-C quintile remained significant for all-cause death (very low: HR 1.29, 95% CI 1.16-1.44, P<0.001; low: HR 1.15, 95% CI 1.03-1.29, P=0.01). There were no significant interactions between the association of LDL-C level with all-cause death and subgroup factors, such as lipid-lowering treatment at index hospitalization, age, sex, acute myocardial infarction presentation, and study cohort. The excess adjusted risks of the lowest LDL-C quintile relative to the intermediate LDL-C quintile were significant for clinical outcomes such as cardiovascular death (HR 1.17, 95% CI 1.01-1.35), non-cardiovascular death (HR 1.35, 95% CI 1.15-1.60), sudden death (HR 1.44, 95% CI 1.01-2.06), and heart failure admission (HR 1.11 95% CI 1.01-1.22), while there was no excess risk for the lowest LDL-C quintile relative to the intermediate LDL-C quintile for myocardial infarction and stroke. Conclusions Lower baseline LDL-C levels were associated with more comorbidities and a significantly higher risk of death, regardless of cardiovascular or non-cardiovascular causes, in patients who underwent coronary revascularization.