Prognostic Value of Systemic Immune‐Inflammation Index (SII) in Hospital Readmission Following Acute Myocardial Infarction: A Four‐Year Analysis

Background Acute myocardial infarction (AMI) initiates an inflammatory response essential for cardiac repair. Several novel inflammatory markers have been identified as indicators of systemic inflammation, including the systemic immune‐inflammation index (SII). This study aimed to evaluate the relationship between SII levels and readmission rates in AMI patients. Methods This retrospective cohort study analyzed 1147 AMI patients admitted between 2019 and 2021. The optimal SII cutoff was determined as 694.3 × 10 9 /L, categorizing patients into high SII (≥ 694.3) and low SII (< 694.3) groups. The association between SII levels and readmission risk was assessed using a logistic regression model. Results Over 4 years, 454 patients were readmitted, with higher readmission rates (34.4%) observed in the high SII group. Statistically significant differences were noted in primary outcomes, with higher SII patients experiencing increased incidence of major adverse cardiovascular events (MACEs) ( p < 0.05). The Cox proportional hazards model indicated that individuals with prior CABG had a 40% higher risk of readmission. Conclusion Although patients with high SII demonstrated higher hospital readmission rates, primarily due to recurrent MI, no statistically significant association was observed.