No-Reflow in Young Acute Coronary Syndrome Patients: Association with the Inflammatory Prognostic Index.

OBJECTIVE: The no-reflow phenomenon (NRP) is an important complication associated with adverse outcomes in patients undergoing PCI for acute coronary syndrome (ACS). Inflammation plays a central role in the pathophysiology of NRP. The inflammatory prognostic index (IPI), calculated using the neutrophil-to-lymphocyte ratio and C-reactive protein-to-albumin ratio, has recently emerged as a novel inflammatory marker. This study aimed to investigate the relationship between IPI and NRP in young patients with ACS undergoing PCI. METHOD: In this single-center retrospective study, a total of 443 consecutive patients aged ≤45 years who underwent PCI for ACS between 2022 and 2025 were included. The study population comprised 305 patients with ST-segment elevation myocardial infarction (STEMI; 68.8%), 126 with non-ST-segment elevation myocardial infarction (NSTEMI; 28.4%), and 12 with unstable angina (2.7%). Laboratory parameters were obtained from the first venous blood sample collected before coronary angiography during the index hospitalization. NRP was defined as a final Thrombolysis in Myocardial Infarction (TIMI) flow grade of 0-2 in the absence of mechanical obstruction or a final TIMI flow grade of 3 with a myocardial blush grade of 0-1. Clinical, laboratory, angiographic, and procedural characteristics were compared according to NRP status. Logistic regression and receiver operating characteristic (ROC) curve analyses were performed to identify independently associated factors and evaluate the discriminatory performance of inflammatory indices. RESULTS: NRP developed in 112 patients (25.3%), whereas 331 patients (74.7%) had normal flow. Patients with NRP had significantly higher IPI levels than those without NRP [6.88 (4.66-12.67) vs. 3.50 (2.03-7.41), P < 0.001]. The multivariable model included IPI modeled using a natural cubic spline with 4 degrees of freedom, STEMI presentation, left anterior descending (LAD) coronary artery as the culprit vessel, serum creatinine, and an initial TIMI flow grade of 0-1. IPI showed a significant nonlinear association with NRP in the multivariable analysis (p for overall association <0.001; p for nonlinearity <0.001). An initial TIMI flow grade of 0-1 and LAD involvement as the culprit vessel also remained independently associated with NRP. In the standalone ROC analysis, IPI demonstrated the highest discriminatory performance among the inflammatory indices evaluated for NRP [area under the curve (AUC): 0.725, 95% confidence interval (CI): 0.677-0.772], with a cutoff value of 3.45, providing 92.0% sensitivity and 49.8% specificity. CONCLUSION: IPI showed a significant nonlinear association with NRP in young patients with ACS undergoing PCI and may provide additional information for identifying patients at increased risk of this procedural complication. However, its relatively low specificity limits its use as a standalone marker, and prospective validation is warranted.