Inflammatory Signatures from the Complete Blood Count and In-Hospital Mortality in Acute Myocardial Infarction

Background/Objectives: Early risk stratification in acute myocardial infarction (AMI) requires accessible and cost-effective tools. Complete blood count-derived inflammatory indices may provide readily available markers of immunothrombotic activity. The objective of this study was to evaluate the association between inflammatory indices derived from the complete blood count at admission and in-hospital mortality among patients with acute myocardial infarction treated at a high-complexity cardiovascular center. Methods: We conducted a retrospective cohort analysis of prospectively collected data from adults with type 1 AMI treated at a high-complexity cardiovascular center in Colombia between 2021 and 2025. Complete blood count parameters at admission were used to calculate hematological inflammatory indices. The primary outcome was all-cause in-hospital mortality. Associations were evaluated using logistic regression models. Discrimination was assessed using ROC curves, and restricted cubic splines and sensitivity analyses were used to evaluate nonlinearity and robustness. Results: Among 3768 patients, 143 (3.8%) died during hospitalization. Non-survivors had higher NLR, SIRI, SII, and AISI values (all p < 0.001). After adjustment, SIRI (OR 1.94, 95% CI 1.62–2.32), NLR (OR 1.89, 95% CI 1.57–2.27), NPR (OR 1.86, 95% CI 1.56–2.22), and AISI (OR 1.83, 95% CI 1.53–2.19) showed the numerically largest adjusted associations with mortality. Discriminatory performance was modest, with the numerically highest AUROC observed for NPR (0.723), followed by SIRI (0.716) and NLR (0.706). Conclusions: Inflammatory indices were associated with in-hospital mortality in type 1 AMI, but their discriminatory ability was modest. These indices may serve as complementary markers of inflammatory risk.