A Newly Defined Inflammatory Predictor of the Postprocedural No-Reflow/Slow-Flow Phenomenon in Patients with Non-ST Segment Elevation Myocardial Infarction: Aggregate Index of Systemic Inflammation

Objective: This study aimed to investigate the relationship between the Aggregate Index of Systemic Inflammation (AISI) and NRF/SF development in non-ST-elevation myocardial infarction (NSTEMI) patients undergoing percutaneous coronary intervention (PCI). Methods: This retrospective observational study included 1092 NSTEMI patients who underwent PCI. Complete blood count-derived inflammatory indices, including the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), lymphocyte-to- monocyte ratio (LMR), and AISI, were calculated before PCI. AISI was calculated using the ‘’neutrophil count x monocyte count x platelet/lymphocyte count’’ formula. NRF/ SF was defined as post- procedural TIMI flow <3 in the absence of mechanical obstruction. The study cohort was divided into 2 groups based on a median AISI score of 298. After determining the parameters associated with NRF/SF through univariate analysis, multivariate logistic regression analysis was performed to identify independent predictors. The De-Long test was conducted to assess the discriminatory ability and predictive performance of inflammation-based indices. Results: A total of 94 (8.6%) patients suffered from NRF/SF, and it was more common in patients with high AISI values compared to those with low values (p< 0.001). Considering the inflammatory parameters, higher NLR (OR= 1.347, p<0.001), higher PLR (OR= 1.003, p=0.017), higher AISI (OR= 1.003, p<0.001) and lower LMR (OR= 0.713, p<0.001) independently predicted the NRF/SF development. De-Long test analysis revealed that AISI has better predictive performance compared to other inflammation-based scores (AUC= 0.703, p<0.001). Conclusion: As an independent predictor of the NRF/SF phenomenon, AISI can serve as a practical and cost-effective biomarker for the early diagnosis of high-risk patients.