Prediction of No-Reflow Phenomenon After Primary Percutaneous Coronary Intervention in Patients With ST-Segment Elevation Myocardial Infarction Using the Systemic Immune-Inflammation Index/HDL Ratio

Background: The no-reflow phenomenon following primary percutaneous coronary intervention (PPCI) in patients with ST-segment elevation myocardial infarction (STEMI) is associated with adverse clinical outcomes. Inflammatory activation and microvascular dysfunction play key roles in its pathophysiology. The systemic immune-inflammation index (SII) integrates neutrophil, platelet, and lymphocyte counts, while high-density lipoprotein cholesterol (HDL-C) reflects anti-inflammatory capacity. Results: This observational study included 150 STEMI patients undergoing PPCI. No-reflow occurred in 41 patients (27.3%). Patients with no-reflow had significantly higher neutrophil counts, platelet counts, C-reactive protein levels, SII values, and SII/HDL ratios, and significantly lower lymphocyte counts and HDL-C levels (all p < 0.001). The SII/HDL ratio was significantly higher in the no-reflow group (56.6 ± 20.6 vs. 28.4 ± 19.8). Receiver operating characteristic analysis demonstrated good predictive value of SII/HDL for no-reflow (AUC 0.80). A cut-off value >25.25 showed 82.9% sensitivity and 77.1% specificity. On multivariable logistic regression analysis, SII/HDL >25.25 was an independent predictor of no-reflow (OR 16.32, 95% CI 6.45–41.28, p < 0.001). Conclusions: The SII/HDL ratio is a strong independent predictor of the no-reflow phenomenon following PPCI in STEMI patients. This simple, readily available biomarker may assist in early risk stratification and optimization of reperfusion strategies.