Associations Between Albumin-Corrected Anion Gap and Mortality in Heart Failure Patients with Chronic Obstructive Pulmonary Disease: A Retrospective Cohort Study.

BACKGROUND: Heart failure (HF) and chronic obstructive pulmonary disease (COPD) are common comorbidities in intensive care unit (ICU) patients. The albumin-corrected anion gap (ACAG) has shown utility in predicting mortality across various populations; however, its impact on HF patients with COPD remains unclear. This study investigated the relationship between ACAG and mortality in this population.

METHODS: We conducted a retrospective cohort study using the Medical Information Mart for Intensive Care (MIMIC)-IV database. A total of 1283 patients with heart failure and chronic obstructive pulmonary disease were included from the MIMIC-IV database. ACAG levels were assessed within 24 hours of admission. The association between ACAG and in-hospital and 30-day mortality was analyzed using Kaplan-Meier analysis, multivariate Cox regression, restricted cubic spline (RCS) analysis, subgroup analysis, and receiver operating characteristic (ROC) curve analysis.

RESULTS: Among 1283 HF patients with COPD (54.6% male), in-hospital and 30-day mortality rates were 11.2% and 13.7%, respectively. Kaplan-Meier analysis demonstrated significantly increased mortality risk in patients with higher ACAG levels (log-rank P<0.001). In fully adjusted Cox models, compared to the lowest ACAG group (T1), the highest group (T3) showed hazard ratios of 2.04 (95% CI: 1.18-3.54; p=0.011) for in-hospital mortality and 1.83 (95% CI: 1.12-2.97; p=0.015) for 30-day mortality. RCS analysis revealed a linear relationship between ACAG and mortality risk, consistent across subgroups. ROC analysis demonstrated superior discriminatory ability of ACAG for in-hospital mortality (AUC=0.693) compared to anion gap (AUC=0.571) and albumin (AUC=0.640), with similar findings for 30-day mortality.

CONCLUSION: ACAG is closely associated with the risk of mortality in HF patients with COPD. It appears to be a potential prognostic predictor for HF patients with COPD, aiding in risk stratification for this population. However, further prospective studies are needed to consolidate our findings.