Association between RDW-to-albumin ratio and mortality in HFpEF: a retrospective study based on MIMIC-IV and external...

Heart failure with preserved ejection fraction (HFpEF) in the intensive care unit (ICU) has high mortality, yet reliable bedside prognostic markers remain limited. The red cell distribution width-to-albumin ratio (RDW/Alb), reflecting inflammation and nutrition, has not been validated in this setting.

This retrospective cohort study queried the MIMIC-IV (v2.2) database for adults (≥18 years) with first ICU admission and HFpEF (left ventricular ejection fraction ≥50% by ICD coding or echocardiographic narrative). RDW and serum albumin within 24 h of ICU entry were used to calculate RDW/Alb, analyzed as tertiles (T1 ≤ 4.08; T2 4.08-5.13; T3 > 5.14). The primary endpoint was all-cause mortality at 30, 90, and 365 days. Kaplan-Meier curves, multivariable Cox regression, restricted cubic splines (RCS), and subgroup analyses were conducted. Prognostic discrimination of RDW/Alb was compared with the triglyceride-glucose (TyG) index in a biomarker-complete subset. Findings were externally validated in 429 HFpEF patients from general wards at our hospital.

Among 3,436 ICU-HFpEF patients, 659 (19.2%), 907 (26.4%), and 2,997 (87.3%) deaths occurred at 30, 90, and 365 days, respectively. Mortality rose stepwise across tertiles (30-day: 8.0% vs 16.2% vs 33.3%; log-rank < 0.001). In fully adjusted models, each unit increase in RDW/Alb was associated with 12% higher hazard for 30-day (HR 1.12, 95% CI 1.10-1.15) and 90-day mortality (HR 1.12), and a 10% increase for 1-year mortality (HR 1.10, 95% CI 1.07-1.12). Compared with T1, T3 patients had HRs of 3.13, 3.02, and 1.37 for 30-, 90-, and 365-day mortality (all p < 0.001). RCS revealed a nonlinear risk surge above an RDW/Alb of 4.56. The association remained across subgroups and was stronger in females, non-diabetics, and non-statin users (interaction < 0.01). In 490 patients with glucose and triglyceride data, RDW/Alb outperformed TyG in predicting mortality (AUC 0.67-0.68 vs 0.52-0.54; p < 0.01). External validation confirmed RDW/Alb as a predictor of 1-year mortality (HR for T3 vs T1: 2.90; 95% CI: 1.55-5.41; p < 0.001).

RDW/Alb is a simple, widely available marker that strongly predicts mortality in ICU patients with HFpEF, outperforming TyG and supporting its role in early risk stratification.