Platelet-To-Lymphocyte Ratio and 28-Day Survival in Critically Ill Patients With Pulmonary Hypertension: Insights From a MIMIC-IV Retrospective Analysis.

AIMS/BACKGROUND: Existing pulmonary arterial hypertension (PAH) risk stratification, based on hemodynamics and functional parameters, is often inadequate in critical illness. The platelet-to-lymphocyte ratio (PLR), reflecting inflammatory and thrombotic pathways, may enhance outcome prediction. This study aimed to determine the prognostic value of PLR for 28-day mortality in critically ill PAH patients, evaluate nonlinear thresholds, and validate predictive performance using machine learning. METHODS: A retrospective cohort of 1512 PAH patients was extracted from the Medical Information Mart for Intensive Care IV (MIMIC-IV) v3.0 database (2008-2022). PLR was derived from admission hematologic parameters. Multivariable Cox regression, restricted cubic spline (RCS) models, and machine learning algorithms were employed to assess associations between PLR and mortality. CONCLUSION: PLR represents an independent predictor of short-term mortality in critically ill PAH patients, with nonlinear thresholds offering actionable risk stratification. Integration of PLR into prognostic models may strengthen early risk assessment and guide timely interventions in critical care settings.