Pan-immune-inflammation value for risk stratification of adverse cardiovascular outcomes in acute coronary syndrome undergoing percutaneous coronary intervention: a systematic review and meta-analysis

Background: Patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI) remain at residual cardiovascular risk. The pan-immune-inflammation value (PIV), integrating neutrophil, platelet, monocyte, and lymphocyte counts, has been proposed as a candidate prognostic biomarker in this population, but the evidence has not been formally synthesised. We evaluated the prognostic and discriminatory value of PIV in adults with ACS undergoing PCI. Methods: PubMed/MEDLINE, Embase, Web of Science Core Collection, the Cochrane Library, Scopus, and CNKI were searched from inception, supplemented by trial registries, Google Scholar, and reference hand-searching. Cohort studies reporting associations between PIV and major adverse cardiovascular events (MACE; primary outcome), all-cause mortality, cardiovascular or cardiac mortality, angiographic no-reflow or slow-flow, or post-contrast renal injury were eligible. Two reviewers independently performed study selection, data extraction, and QUIPS risk-of-bias assessment. Adjusted hazard ratios, odds ratios, and AUC values were pooled separately using random-effects models; certainty was rated with GRADE. PROSPERO: CRD420261378751. Results: Nineteen cohort studies (n = 18,715) were included. Higher PIV was associated with study-defined MACE (adjusted HR 1.65, 95% CI 1.20-2.27; k = 2; I² = 0.0%; low certainty) and all-cause mortality (HR 3.51, 95% CI 2.15-5.74; k = 2; I² = 0.0%; moderate certainty). A single study reported an association with cardiac mortality (HR 3.24, 95% CI 1.34-7.81; low certainty). PIV showed consistent discrimination for no-reflow or slow-flow (AUC 0.828, 95% CI 0.808-0.846; k = 2; I² = 0.0%; moderate certainty) and heterogeneous discrimination for post-contrast renal injury (AUC 0.771, 95% CI 0.617-0.875; k = 5; I² = 95.1%; very low certainty). Risk of bias was moderate in 16 studies and high in three. Conclusion: Elevated PIV may be associated with adverse cardiovascular outcomes in ACS patients undergoing PCI, particularly long-term all-cause mortality and angiographic no-reflow or slow-flow. However, evidence is limited by observational designs, small numbers of studies for several outcomes, heterogeneous cut-offs, and risk-of-bias concerns. PIV should be regarded as a promising supplementary marker requiring prospective multicentre validation, comparison with established inflammatory indices, and assessment of incremental value beyond GRACE or TIMI before routine clinical use. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/, identifier CRD420261378751.