Association between lactate-to-albumin ratio and 28-day mortality in critically ill patients with HFpEF: a retrospectively cohort study

Previous studies have established associations between elevated lactate-to-albumin ratio (LAR) and mortality in sepsis or critically ill populations. However, its prognostic significance specifically among heart failure with preserved ejection fraction (HFpEF) patients remains underexplored. This study aims to elucidate the relationship between LAR and 28-day all-cause mortality in critically ill patients with HFpEF. This retrospective cohort study derived 731 critically ill HFpEF patients from the Medical Information Mart for Intensive Care IV (MIMIC-IV, v3.1) database. Demographic characteristics, comorbidities, laboratory parameters, clinical severity indices, and mortality outcomes were systematically extracted. Participants were subsequently stratified into LAR tertiles: T1 (< 0.363), T2 (0.363-0.593), and T3 (> 0.593). We employed Cox proportional hazards regression and restricted cubic spline (RCS) analyses to evaluate associations between LAR and 28-day mortality. Sensitivity analyses and comorbidity-stratified subgroup assessments verified result robustness and examined interaction effects. Receiver operating characteristic (ROC) curve analysis assessed LAR's discriminative performance for 28-day mortality prediction. Within the final cohort of 731 HFpEF patients, 103 (14.1%) experienced 28-day mortality following ICU admission. A pronounced mortality gradient emerged across LAR tertiles (T1:10.3%; T2:10.7%; T3:21.3%; P < 0.001). Kaplan-Meier analysis confirmed significantly reduced survival probability with elevated LAR, persisting after adjustment for age, sex, race and BMI (log-rank P = 0.019). Unadjusted Cox regression demonstrated significant LAR-mortality associations. However, multivariable adjustment attenuated statistical significance for both continuous (HR 1.31, 95% CI 0.80-2.16; P = 0.290) and categorical comparisons (T3 vs. T1: HR 1.34, 95% CI 0.71-2.53; P = 0.373). RCS and sensitivity analyses corroborated these patterns. Significant interaction effects emerged between LAR and race, BMI, myocardial infarction, chronic pulmonary disease, chronic kidney disease, and hypertension (P < 0.05). ROC analysis indicated modest discriminatory capacity for 28-day mortality prediction (AUC 0.625, 95% CI 0.566-0.685). In this cohort of critically ill patients with HFpEF, it's demonstrated a positive correlation between LAR and the risk of 28-day all-cause mortality. However, our study did not confirm LAR as an independent predictor of mortality in HFpEF after comprehensive adjustment. Instead, the findings position LAR as a composite biomarker reflecting global disease severity.