Serum total calcium levels as a non-linear predictor of in-hospital mortality in heart failure patients: insights from a retrospective cohort study

Calcium is pivotal in the regulation of bodily homeostasis, with numerous studies highlighting its link to cardiovascular disease in the adult population. However, the relationship between serum calcium levels and the prognosis of heart failure (HF) patients is not clear. This study explored the association between serum total calcium (STC) and in-hospital mortality in patients with HF.

Clinical data of 1,176 patients with HF were obtained from the Multiparametric Intelligent Monitoring in Intensive Care III (MIMIC-III) database. The patients were categorized into STC quartiles, and baseline characteristics were comprehensively analyzed. Univariate and multivariate analyses were employed to identify factors associated with in-hospital mortality. To explore the non-linear relationship between STC and mortality, a two-piecewise linear regression model was applied. Subgroup analyses were conducted to identify potential confounding variables.

In this cohort, 159 (13.53%) patients experienced in-hospital mortality. Significant differences in various parameters were observed among STC quartiles. Univariate analysis identified numerous factors associated with mortality. Multivariate analysis confirmed STC as an independent predictor of in-hospital mortality, with a negative association persisting even after adjusting for confounding factors (odds ratio [OR]: 0.49, 95%CI: 0.32–0.76; P = 0.0016). Non-linear analysis revealed an inflection point at 8.41 mg/dL, below which the risk of in-hospital death significantly increased (OR: 0.26, 95%CI: 0.12–0.55; P = 0.0005). Subgroup analyses indicated a pronounced inverse association in patients without atrial fibrillation or chronic obstructive pulmonary disease, as well as those with a left ventricular ejection fraction ≤ 50%.

This study identified STC as an independent predictor of in-hospital mortality in HF patients, with a non-linear relationship.