Prognostic Value of Dynamic Hematologic Immune-Inflammatory Indices in Patients Undergoing Isolated Coronary Artery Bypass Grafting

Background: Despite advances in surgical and perioperative care, early mortality and postoperative complications after isolated coronary artery bypass grafting (CABG) remain clinically relevant. Conventional risk models primarily reflect baseline clinical and operative characteristics and may not fully capture the dynamic immune-inflammatory response to cardiopulmonary bypass and surgical trauma. Hematologic indices derived from routine complete blood counts may provide a practical and low-cost assessment of this perioperative inflammatory burden. Methods: This single-center retrospective observational study included 650 adult patients who underwent isolated CABG between 2020 and 2024. Preoperative and postoperative monocyte-to-lymphocyte ratio (MLR), pan-immune-inflammation value (PIV), and delta neutrophil index (DNI) were evaluated. The primary outcome was in-hospital mortality, and the secondary outcome was a composite postoperative adverse event comprising prolonged mechanical ventilation, prolonged intensive care unit stay, prolonged inotropic support, pneumonia, or sepsis. Results: In-hospital mortality occurred in 52 patients (8.0%), and composite postoperative adverse events occurred in 221 patients (34.0%). Non-survivors were older and had higher clinical risk scores, lower ejection fraction, longer cardiopulmonary bypass and aortic cross-clamp times, and less favorable renal and inflammatory profiles. Preoperative and postoperative MLR, PIV, and DNI were significantly higher in non-survivors after false discovery rate correction. In univariable analyses, DNI showed the strongest associations with mortality; however, none of the immune-inflammatory indices remained independently associated with mortality or composite postoperative adverse events after multivariable adjustment. Among individual biomarkers, postoperative DNI showed the highest discrimination for in-hospital mortality (AUC 0.765, 95% CI 0.692–0.838), followed by preoperative DNI (AUC 0.738). Addition of postoperative DNI to the clinical mortality model increased the AUC from 0.805 to 0.815, although the incremental improvement was not statistically significant. Conclusions: Although perioperative MLR, PIV, and DNI were associated with adverse outcomes in unadjusted analyses, none remained independently associated with in-hospital mortality or composite postoperative adverse events after multivariable adjustment. Postoperative DNI showed the strongest individual discrimination for mortality; however, its addition to the clinical model resulted in only a small and statistically non-significant improvement in AUC. These findings indicate limited incremental prognostic value of the evaluated immune-inflammatory indices beyond established clinical and operative risk factors and do not support their use as stand-alone predictors after isolated CABG.