Independent prognostic importance of the albumin-corrected anion gap in critically ill patients with congestive heart failure: a retrospective study from MIMIC-IV database.

Background: The associations between the albumin-corrected anion gap (ACAG) and all-cause mortality in patients with congestive heart failure in the intensive care unit remain uncertain. This study aimed to investigate this unknown.

Methods: The MIMIC-IV (version 3.0) database was used to analyze critically ill patients with congestive heart failure. Patients were grouped into tertiles (T1-T3) on the basis of the ACAG. The association between ACAG levels and 1-year all-cause mortality was assessed using Kaplan-Meier survival analyses, multivariate adjusted Cox regression models, and restricted cubic spline curves. An analysis of subgroups was performed to evaluate ACAG's prognostic impact across diverse populations. Mediation analysis was conducted to identify and elucidate potential causal pathways linking ACAG to all-cause mortality.

Results: A cohort of 7787 patients was analyzed. On the basis of Kaplan-Meier curves, Cox regression, restricted cubic spline curves and subgroup analysis, T2 (hazard ratio 1.09, 95% confidence interval 1.02 ~ 1.16) and T3 (hazard ratio 1.25, 95% confidence interval 1.17 ~ 1.33) individuals presented a greater mortality risk compared to T1 individuals (p for linear trend < 0.001), and most subgroups consistently observed this relationship, except for those with different levels of left ventricular ejection fraction. Mediation analysis indicated that the red cell distribution width, stage of acute kidney injury, chloride and acute physiology score III partially mediated the relationship between ACAG and mortality, accounting for 12.4%, 7.0%, 12.9%, and 31.2% of the mediating effect, respectively.

Conclusions: The ACAG was associated with higher 1-year all-cause mortality in critically ill patients with congestive heart failure, with stronger impact in those with lower left ventricular ejection fractions. The ACAG may serve as an indicator in high-risk groups.

Clinical trial number: Not applicable.