Impact of Low-Density Lipoprotein Cholesterol Levels at Acute Coronary Syndrome Admission on Long-Term Clinical Outcomes

Aim: Low-density lipoprotein cholesterol (LDL-C) level reduction is highly effective in preventing the occurrence of a cardiovascular event. Contrariwise, an inverse association exists between LDL-C levels and prognosis in some patients with cardiovascular diseases-the so-called "cholesterol paradox." This study aimed to investigate whether the LDL-C level on admission affects the long-term prognosis in patients who develop acute coronary syndrome (ACS) and to examine factors associated with poor prognosis in patients with low LDL-C levels.Methods: We enrolled 410 statin-naive patients with ACS, whom we divided into low- and high-LDL-C groups based on an admission LDL-C cut-off (obtained from the Youden index) of 122 mg/dL. Endothelial function was assessed using the reactive hyperemia index 1 week after statin initiation. The primary composite endpoint included all-cause death, as well as myocardial infarction and ischemic stroke occurrences.Results: During a median follow-up period of 6.1 years, 76 patients experienced the primary endpoint. M ultivariate Cox regression analysis revealed that patients in the low LDL-C group had a 2.3-fold higher risk of experiencing the primary endpoint than those in the high LDL-C group (hazard ratio, 2.34; 95% confidence interval, 1.29-4.27; p=0.005). In the low LDL-C group, slow gait speed (frailty), elevated chronic-phase highsensitivity C-reactive protein levels (chronic inflammation), and endothelial dysfunction were significantly associated with the primary endpoint.Conclusions: Patients with low LDL-C levels at admission due to ACS had a significantly worse long-term prognosis than those with high LDL-C levels; frailty, chronic inflammation, and endothelial dysfunction were poor prognostic factors.