Elevated Cystatin-C Levels Are Associated with Increased Mortality in Acute Coronary Syndrome Patients: An HIJ-PROPER Sub-Analysis

Background and Aims: We investigated the association between serum cystatin-C (Cys-C) levels and cardiovascular events in patients with acute coronary syndrome (ACS). Methods: Data of 1,100 patients from the prospective parent study were included. Patients hospitalized for ACS were divided into 4 groups based on quartiles (Q) of Cys-C levels (mg/L) within 24 h of admission: Q1, ≤0.82; Q2, 0.82 < estimated level ≤0.95; Q3, 0.95< estimated level ≤1.12; and Q4, >1.12. The primary endpoint of this study was all-cause mortality, and the secondary endpoint was composite of all-cause mortality, nonfatal myocardial infarction, nonfatal stroke, unstable angina pectoris, or ischemia-driven revascularization. Results: During a median observation period of 4.0 years, the primary endpoint was noted in 5, 12, 18, and 36 patients in Q1–Q4, respectively, with corresponding incidence rates of 1.8%, 4.4%, 6.5%, and 13.5%, respectively ( p < 0.0001 for difference among 4 groups). This association persisted even after adjusting for patient characteristics and other laboratory results at baseline ( p = 0.04). A stepwise increase in the incidence rate of the secondary endpoint with an incline in Cys-C levels was observed in the nonadjusted model (26.6%, 33.3%, 32.3%, and 39.1% in Q1–Q4, respectively; p = 0.01) but not in the adjusted model ( p = 0.3). No difference was observed in the incidence rate of nonfatal myocardial infarction ( p = 0.89), nonfatal stroke ( p = 0.3), unstable angina pectoris ( p = 0.49), and ischemia-driven revascularization ( p = 0.47) with an incline in Cys-C levels. Conclusion: Elevated Cys-C levels were associated with increased all-cause mortality but not cardiovascular events other than mortality in ACS patients.