Association Between Alkaline Phosphatase Levels and All‐Cause Mortality in Critically Ill Patients With Acute Myocardial Infarction Combined Heart Failure: A Retrospective Study Using the MIMIC Database

Background Alkaline phosphatase (ALP) is implicated in vascular calcification and inflammation, yet its prognostic role in acute myocardial infarction (AMI) complicated by heart failure (HF) remains uncertain. This study aimed to examine the association between ALP levels and all‐cause mortality in critically ill patients with AMI and HF. Methods A total of 2327 adult patients diagnosed with AMI and HF from the MIMIC‐III and MIMIC‐IV databases were included and categorized into quartiles (Q1–Q4). The primary outcome was 1‐year mortality, with hospital and ICU mortality as secondary outcomes. Cox proportional hazards models and restricted cubic splines (RCS) were used to assess the association between ALP and mortality. Kaplan–Meier curves compared secondary outcomes across quartiles. Results Among the 2327 patients (62.40% male), hospital and ICU mortality rates were 19.80% and 13.80%, respectively. Kaplan–Meier analysis showed significantly higher mortality in patients with elevated ALP ( p < 0.0001). In Cox analyses, the highest ALP quartile (Q4) was associated with increased hazard of hospital mortality (HR: 1.486; 95% CI: 1.142–1.935; p = 0.003) and ICU mortality (HR: 1.400; 95% CI: 1.030–1.910; p = 0.034). RCS revealed a U‐shaped relationship between ALP and mortality, with increased risk observed at both low and high ALP levels ( p ‐nonlinearity < 0.001). Conclusion Elevated ALP is an independent predictor of mortality in critically ill patients with AMI and HF, highlighting its potential role in risk stratification and clinical management.