Association Between Inflammatory Indices and Major Adverse Events After Coronary Artery Bypass Surgery: A Retrospective Cohort Study

Background: Coronary artery bypass grafting (CABG) is associated with a significant risk of postoperative major adverse event (MAE), largely driven by systemic inflammatory responses. Easily accessible inflammatory indices such as the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), and plateletcrit (PCT) have been proposed as potential predictors; however, the comparative performance and optimal timing of these indices remain unclear. Thus, this study aimed to evaluate the association between perioperative inflammatory indices measured at different time points and postoperative MAEs in patients undergoing elective on-pump CABG, and to compare the discriminatory performance of these indices. Methods: This single-center retrospective cohort study included 500 patients who underwent elective on-pump CABG between January 2022 and December 2023. Inflammatory indices (NLR, PLR, SII, and PCT) were calculated preoperatively and on postoperative days 0 (POD0), 1, and 3. The primary outcome was MAE, defined as mortality, stroke, sepsis, or acute kidney injury (AKI). Multivariable logistic regression and receiver operating characteristic curve analyses were performed to assess independent associations and discriminatory performance. Results: MAE occurred in 120 patients (24.0%) and were predominantly driven by AKI. Meanwhile, inflammatory indices measured on PODs0 and 1 showed limited discriminative ability. Conversely, NLR on POD3 was independently associated with MAE (odds ratio (OR): 1.16 per unit increase; 95% confidence interval (CI): 1.11–1.22; p < 0.001) and demonstrated the highest discriminatory performance (area under the curve (AUC): 0.733), followed by SII and PLR, whereas PCT showed poor performance. A cut-off value of NLR ≥10 on POD3 was associated with a significantly increased risk of MAE (OR: 3.98, 95% CI: 2.49–6.37; p < 0.001) and AKI (OR: 3.44, 95% CI: 2.09–5.66; p < 0.001). Conclusions: The prognostic value of inflammatory markers after CABG is time-dependent. NLR measured on POD3 showed the strongest and most consistent association with adverse outcomes and may serve as a practical tool for postoperative risk stratification, particularly for AKI. However, given the potential influence of reverse causality, these findings should be confirmed in prospective, multicenter studies.