Systemic Immune-Inflammation Index Predicts Long-Term Outcomes in Patients with Three-Vessel Coronary Disease After Revascularization: Results from a Large Cohort of 3561 Patients

Objective: This study aimed to investigate the prognostic value of systemic immune inflammation index (SII) concerning long-term outcomes in patients with the three-vessel disease (TVD) after revascularization in a large cohort. Methods: In total, 3561 TVD patients who had undergone revascularization between 2013 and 2018 were included in the study. Patients were divided into the low SII (< 694.3 × 10 9 /L) (n = 2556, 71.8%) and the high SII (≥ 694.3 × 10 9 /L) group (n = 1005, 28.2%). The C-index, net reclassification improvement (NRI), and integrated discrimination improvement (IDI) were calculated to assess whether the addition of SII to a baseline model with traditional risk factors improved the accuracy of cardiac event prediction. The primary outcome was the frequency of major adverse and cerebrovascular events (MACCE). The secondary outcome was the incidence of all-cause death. Results: After 2.4 years of follow-up, the Cox proportional hazard regression model analysis displayed that high SII was independently associated with an increased risk of developing future MACCE (hazard ratio [HR] 1.65, 95% confidence interval [CI] 1.23– 2.21, p = 0.001) and all-cause death (HR: 2.96; 95% CI: 1.19– 7.32, p = 0.019). The addition of SII significantly improved the reclassification beyond the baseline model with traditional risk factors (MACCE: NRI, 0.115; p = 0.0001; all-cause death: NRI, 0.369; p = 0.0001). Reclassification with the addition of SII also demonstrated an IDI of 0.0022 (p = 0.006) in MACCE and 0.0033 (p = 0.014) in all-cause death. Conclusion: In TVD patients after revascularization, increased SII is an independent prognostic factor for long-term outcomes of MACCE and death. Compared to traditional risk factors, SII improved the risk prediction of major cardiovascular events in TVD patients who underwent revascularization.