Elevated Serum Alkaline Phosphatase as an Independent Predictor of Mortality Among Heart Failure Patients in the Intensive Care Unit: A MIMIC-IV Database Analysis

Background Heart failure (HF) is an end-stage disease frequently necessitating intensive care unit (ICU) treatment and is associated with elevated serum alkaline phosphatase (ALP); however, the prognostic significance for HF-associated mortality among ICU patients remains unexplored. Methods This retrospective cohort study examined associations between ALP and mortality using the Medical Information Mart for Intensive Care IV (version 2.2) database. This cohort study analyzed 4,569 adults diagnosed with HF who were admitted to the ICU and were included in the Medical Information Mart for Intensive Care IV (version 2.2) database from 2008 to 2019. Patients aged < 18 years, those who died or were discharged within 24 h, and those with missing key variables were excluded. Demographic and clinical data were collected within the first 24 h of ICU admission and evaluated using Kaplan–Meier and Cox proportional-hazard models adjusted for major covariates. Results ICU mortality rate for HF was 11.45% (523 deaths), in-hospital rate was 17.22% (787 deaths), and total rate was 53.38% (2,439 deaths). Kaplan–Meier analysis revealed significantly greater ICU, in-hospital, and total mortality rates among HF patients with ALP > 140 IU/L (all p < 0.001). Both continuous and categorical ALP elevations (> 140 vs. ≤140 IU/L) were significantly associated with ICU, in-hospital, and total mortality by Cox regression analysis, and multivariate analysis established ALP as an independent predictor of all three mortality categories. Multivariate analysis revealed that when ALP was modeled as a continuous variable, each 100-IU/L increase in ALP was associated with adjusted hazard ratios (HRs) of 1.076 for ICU mortality, 1.078 for in-hospital mortality, and 1.080 for total mortality. Categorical analysis (ALP of > 140 vs. ≤140 IU/L) revealed that the adjusted HRs increased to 1.293, 1.258, and 1.318, respectively. Conclusions Increased blood ALP levels were substantially correlated with higher mortality in heart failure patients necessitating ICU care. These findings underscore the need for further research on the mechanisms underlying ALP elevation in HF.