The incremental prognostic effect of red blood cell distribution width in 28-day mortality among critically ill patients with HFpEF

Background The prognostic impact of red blood cell distribution width (RDW) on adverse outcomes in patients with heart failure with preserved ejection fraction (HFpEF) has been established. However, its non-linear relationship and incremental prognostic value in critically ill HFpEF patients remain insufficiently explored. Methods A retrospective cohort study was conducted involving 3802 HFpEF patients from the Medical Information Mart for Intensive Care IV (MIMIC-IV, v3.1) database. Multivariable Cox regression and restricted cubic spline (RCS) analyses were performed to evaluate the association between RDW and 28-day mortality, adjusting for potential confounders. A prediction model was constructed by the least absolute shrinkage and selection operator (Lasso)-Cox regression, and receiver operating characteristic (ROC) curve was utilized to assessed the incremental prognostic effect of RDW on 28-day mortality prediction. Results Within the final cohort of 1962 HFpEF patients, the incidence of 28-day mortality showed a significant increase across RDW tertiles (T1 9.4% vs T2 13.1% vs T3 22.9%, P < 0.001). The Kaplan-Meier analysis demonstrated significantly higher all-cause mortality risk among patients with higher RDW levels (log-rank P < 0.001). Multivariable Cox regression analysis revealed that RDW levels were independently correlated with all-cause mortality after adjusting for multiple variables for both continuous (HR 1.13, 95% CI: 1.07–1.19; P < 0.001) and categorical comparisons (T3 vs T1: HR 1.66, 95% CI: 1.20–2.29; P = 0.002). RCS analysis indicated a significant linear relationship between RDW levels and the risk of mortality ( P < 0.001 for overall association; P = 0.222 for non-linearity). When RDW was incorporated into the basic prediction model constructed by Lasso-Cox regression (AUC = 0.814), it slightly improved the predictive ability for 28-day mortality (AUC = 0.819), as evidenced by an IDI of 0.017 (95% CI: 0.006–0.036) and an NRI of 0.140 (95% CI: 0.041–0.203). Conclusions This study established a significant linear association between RDW at admission and poor prognosis in critically ill patients with HFpEF. Higher RDW levels were associated with increased 28-day mortality risk, suggesting that it may be a relevant biomarker for mortality risk stratification in HFpEF patients.