The hemoglobin–to–red cell distribution width ratio to predict all–cause mortality in patients with acute myocardial infarction in the MIMIC–IV database

Background The hemoglobin – to – red cell distribution width ratio (HRR) has emerged as a promising prognostic biomarker in various critical illnesses, yet its role specifically in acute myocardial infarction (AMI) remains underexplored. This study aimed to investigate the association between HRR and all–cause mortality in critically ill patients with AMI. Methods Clinical data were extracted from the Medical Information Mart for Intensive Care IV (MIMIC – IV) database. Patients with AMI were enrolled and stratified into three tertiles based on their HRR levels (T1: HRR ≤ 0.66, T2: 0.66 < HRR < 0.85, T3: HRR ≥ 0.85). The outcomes were in–hospital and 90 – day all – cause mortality. Cox proportional hazards regression models, restricted cubic spline (RCS) analysis, and Kaplan – Meier survival curves were employed to evaluate the association between HRR and mortality risk. Subgroup analyses were conducted to assess the robustness of the findings. Results A total of 4,213 AMI patients were included, with a median age of 72.35 years, and 63.11% were male. Patients in the higher HRR tertile (T2 and T3) exhibited significantly lower mortality compared to those in the lowest tertile (T1). After multivariable adjustment, higher continuous HRR was independently associated with reduced in – hospital mortality (adjusted HR: 0.46, 95% CI: 0.24 – 0.86, P = 0.016) and 90 – day mortality (adjusted HR: 0.19, 95% CI: 0.12 – 0.31, P < 0.001). RCS analysis revealed a non – linear association between HRR and 90 – day mortality risk, with risk decreasing continuously as HRR increased above the Youden – derived cutoff of 0.74 and no plateau observed. Kaplan – Meier survival curves indicated significantly better survival for patients in higher HRR tertiles (log – rank P < 0.001). Subgroup analyses confirmed the consistent protective association of elevated HRR, with significant interaction observed for sepsis. Conclusion HRR is an independent prognostic marker for patients with AMI, and lower HRR levels may be associated with increased short – term mortality. As a readily available and cost – effective biomarker derived from routine laboratory testing, HRR may serve as a valuable tool for early risk stratification in AMI patients.