Association Between the Aggregate Index of Systemic Inflammation (AISI) and Tirofiban Use During Primary Percutaneous Coronary Intervention in Patients with ST-Elevation Myocardial Infarction

<i>Background and Objectives</i>: Inflammation contributes to plaque rupture and thrombosis in ST-elevation myocardial infarction (STEMI). The Aggregate Index of Systemic Inflammation (AISI) is a novel biomarker that reflects innate immune and thrombotic activation. Due to the connection between inflammation and thrombosis, higher AISI values could indicate a greater thrombus burden and the necessity of glycoprotein IIb/IIIa inhibitors. The aim of this study was to assess the relationship between AISI and tirofiban use during primary percutaneous coronary intervention (PCI) in STEMI patients. <i>Materials and Methods</i>: This retrospective study included 2624 STEMI patients who underwent primary PCI at a tertiary heart center between 2019 and 2024. Patients with pre-hospital fibrinolysis, missing laboratory data, or rescue PCI were excluded. AISI was calculated as (neutrophil × monocyte × platelet)/lymphocyte. The primary outcome was tirofiban use during PCI. Univariate and multivariable logistic regression analyses were performed to identify independent predictors, and receiver operating characteristic (ROC) curve analysis was used to evaluate AISI performance. Statistical significance was defined as <i>p</i> < 0.05. <i>Results</i>: Among the 2624 patients with STEMI undergoing primary PCI, tirofiban was administered in 23.5% of cases. Patients receiving tirofiban had significantly higher AISI values (<i>p</i> < 0.001). ROC analysis demonstrated that AISI predicted tirofiban use with a modest discriminative performance (AUC = 0.566; 95% CI 0.536-0.596; <i>p</i> < 0.001). In multivariable logistic regression, younger age (OR 0.98; <i>p</i> < 0.001), higher AISI (per 100-unit increase; OR 1.01; <i>p</i> = 0.037), and lower LVEF (OR 0.98; <i>p</i> < 0.001) independently predicted tirofiban use, whereas admission glucose showed only borderline significance (<i>p</i> = 0.089). <i>Conclusions</i>: Elevated AISI was independently associated with tirofiban use during primary PCI, indicating that systemic inflammatory status parallels intraprocedural decision-making in STEMI. Although its discriminative performance was modest, AISI reflects systemic inflammatory-thrombotic activation in this clinical setting.