Association Between Lactate-to-Calcium Ratio and 28-Day Mortality in Patients With Sepsis-Induced Myocardial Injury: A Retrospective Cohort Study Based on the MIMIC-IV Database

Background Patients with sepsis-induced myocardial injury (SIMI) face a high risk of mortality. Although various biomarkers can be used to predict prognosis in SIMI patients, each has certain limitations. This study aimed to investigate the prognostic value of the lactate-to-calcium ratio (LCR) in patients with SIMI. Methods This retrospective cohort study was conducted using data from the MIMIC-IV database. Patients diagnosed with SIMI who were admitted to the ICU were included. The LCR was calculated based on the first arterial blood gas analysis performed within 24 hours of ICU admission. A restricted cubic spline (RCS) model was used to explore the nonlinear relationship between LCR and 28-day mortality. Patients were divided into high and low LCR groups based on the cutoff values, both overall and by sex. Kaplan–Meier survival curves were used to compare 28-day mortality between groups. Stratification analyses were conducted to assess the prognostic value of LCR across different age strata. Results A total of 1,631 patients were included. The RCS model revealed a positive association between higher LCR and increased 28-day mortality. The cut-off values for LCR were 2.96 for the overall population, 2.91 for females, and 2.16 for males. Cox regression analysis showed that high LCR was significantly associated with higher 28-day mortality (log-rank P < 0.001). Age-stratified analysis indicated that LCR had a higher predictive value in patients younger than 65 years. Among males, high LCR was associated with increased 28-day mortality only in those younger than 65. In females, the association was consistent regardless of age. Conclusion A higher LCR is associated with increased 28-day mortality in ICU patients with SIMI. The sex-specific cut-off values (2.91 for females and 2.16 for males) suggest that LCR may serve as a useful prognostic indicator for identifying high-risk patients with sepsis-induced myocardial injury.